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|
//-----------------------------------------------------------------------------
//
// Copyright (C) Microsoft Corporation. All Rights Reserved.
//
//-----------------------------------------------------------------------------
using System;
using System.Collections.Generic;
using System.Numerics;
using Microsoft.Contracts;
using Microsoft.Boogie;
namespace Microsoft.Dafny {
public class Resolver {
public int ErrorCount = 0;
void Error(IToken! tok, string! msg, params object[] args) {
ConsoleColor col = Console.ForegroundColor;
Console.ForegroundColor = ConsoleColor.Red;
Console.WriteLine("{0}({1},{2}): Error: {3}",
tok.filename, tok.line, tok.col-1,
string.Format(msg, args));
Console.ForegroundColor = col;
ErrorCount++;
}
void Error(Declaration! d, string! msg, params object[] args) {
Error(d.tok, msg, args);
}
void Error(Statement! s, string! msg, params object[] args) {
Error(s.Tok, msg, args);
}
void Error(NonglobalVariable! v, string! msg, params object[] args) {
Error(v.tok, msg, args);
}
void Error(Expression! e, string! msg, params object[] args) {
Error(e.tok, msg, args);
}
readonly Dictionary<string!,TopLevelDecl!>! classes = new Dictionary<string!,TopLevelDecl!>();
readonly Dictionary<ClassDecl!,Dictionary<string!,MemberDecl!>!>! classMembers = new Dictionary<ClassDecl!,Dictionary<string!,MemberDecl!>!>();
readonly Dictionary<DatatypeDecl!,Dictionary<string!,DatatypeCtor!>!>! datatypeCtors = new Dictionary<DatatypeDecl!,Dictionary<string!,DatatypeCtor!>!>();
readonly Graph<ModuleDecl!>! importGraph = new Graph<ModuleDecl!>();
public void ResolveProgram(Program! prog) {
// register modules
Dictionary<string,ModuleDecl!> modules = new Dictionary<string,ModuleDecl!>();
foreach (ModuleDecl m in prog.Modules) {
if (modules.ContainsKey(m.Name)) {
Error(m, "Duplicate module name: {0}", m.Name);
} else {
modules.Add(m.Name, m);
}
}
// resolve imports and register top-level declarations
foreach (ModuleDecl m in prog.Modules) {
importGraph.AddVertex(m);
foreach (string imp in m.Imports) {
ModuleDecl other;
if (!modules.TryGetValue(imp, out other)) {
Error(m, "module {0} named among imports does not exist", imp);
} else if (other == m) {
Error(m, "module must not import itself: {0}", imp);
} else {
assert other != null; // follows from postcondition of TryGetValue
importGraph.AddEdge(m, other);
}
}
RegisterTopLevelDecls(m.TopLevelDecls);
}
// check for cycles in the import graph
List<ModuleDecl!> cycle = importGraph.TryFindCycle();
if (cycle != null) {
string cy = "";
string sep = "";
foreach (ModuleDecl m in cycle) {
cy = m.Name + sep + cy;
sep = " -> ";
}
Error(cycle[0], "import graph contains a cycle: {0}", cy);
} else {
// fill in module heights
List<ModuleDecl!> mm = importGraph.TopologicallySortedComponents();
assert mm.Count == prog.Modules.Count; // follows from the fact that there are no cycles
int h = 0;
foreach (ModuleDecl m in mm) {
m.Height = h;
h++;
}
}
// resolve top-level declarations of refinements
foreach (ModuleDecl m in prog.Modules)
foreach (TopLevelDecl decl in m.TopLevelDecls)
if (decl is ClassRefinementDecl)
ResolveTopLevelRefinement((ClassRefinementDecl) decl);
// resolve top-level declarations
Graph<DatatypeDecl!> datatypeDependencies = new Graph<DatatypeDecl!>();
foreach (ModuleDecl m in prog.Modules) {
ResolveTopLevelDecls_Signatures(m.TopLevelDecls, datatypeDependencies);
}
foreach (ModuleDecl m in prog.Modules) {
ResolveTopLevelDecls_Meat(m.TopLevelDecls, datatypeDependencies);
}
// compute IsRecursive bit for mutually recursive functions
foreach (ModuleDecl m in prog.Modules) {
foreach (TopLevelDecl decl in m.TopLevelDecls) {
ClassDecl cl = decl as ClassDecl;
if (cl != null) {
foreach (MemberDecl member in cl.Members) {
Function fn = member as Function;
if (fn != null && !fn.IsRecursive) { // note, self-recursion has already been determined
int n = m.CallGraph.GetSCCSize(fn);
if (2 <= n) {
// the function is mutually recursive (note, the SCC does not determine self recursion)
fn.IsRecursive = true;
}
}
}
}
}
}
}
public void RegisterTopLevelDecls(List<TopLevelDecl!>! declarations) {
foreach (TopLevelDecl d in declarations) {
// register the class/datatype name
if (classes.ContainsKey(d.Name)) {
Error(d, "Duplicate name of top-level declaration: {0}", d.Name);
} else {
classes.Add(d.Name, d);
}
if (d is ClassDecl) {
ClassDecl cl = (ClassDecl)d;
// register the names of the class members
Dictionary<string!,MemberDecl!> members = new Dictionary<string!,MemberDecl!>();
classMembers.Add(cl, members);
foreach (MemberDecl m in cl.Members) {
if (members.ContainsKey(m.Name)) {
Error(m, "Duplicate member name: {0}", m.Name);
} else {
members.Add(m.Name, m);
}
}
} else {
DatatypeDecl dt = (DatatypeDecl)d;
// register the names of the constructors
Dictionary<string!,DatatypeCtor!> ctors = new Dictionary<string!,DatatypeCtor!>();
datatypeCtors.Add(dt, ctors);
foreach (DatatypeCtor ctor in dt.Ctors) {
if (ctors.ContainsKey(ctor.Name)) {
Error(ctor, "Duplicate datatype constructor name: {0}", ctor.Name);
} else {
ctors.Add(ctor.Name, ctor);
}
}
}
}
}
public void ResolveTopLevelRefinement(ClassRefinementDecl! decl) {
// TODO: check for loops in refinement
if (!classes.ContainsKey(decl.RefinedClass.val)) {
Error(decl.RefinedClass, "Refined class declaration is missing: {0}", decl.RefinedClass.val);
} else {
TopLevelDecl! a = classes[decl.RefinedClass.val];
if (!(a is ClassDecl)) {
Error(a, "Refined declaration is not a class declaration: {0}", a.Name);
return;
}
decl.Refined = (ClassDecl!) a;
// TODO: copy over remaining members of a
// TODO: extend with type parameters for refinements
}
}
public void ResolveTopLevelDecls_Signatures(List<TopLevelDecl!>! declarations, Graph<DatatypeDecl!>! datatypeDependencies) {
foreach (TopLevelDecl d in declarations) {
allTypeParameters.PushMarker();
ResolveTypeParameters(d.TypeArgs, true, d);
if (d is ClassDecl) {
ResolveClassMemberTypes((ClassDecl)d);
} else {
ResolveCtorTypes((DatatypeDecl)d, datatypeDependencies);
}
allTypeParameters.PopMarker();
}
}
public void ResolveTopLevelDecls_Meat(List<TopLevelDecl!>! declarations, Graph<DatatypeDecl!>! datatypeDependencies) {
foreach (TopLevelDecl d in declarations) {
allTypeParameters.PushMarker();
ResolveTypeParameters(d.TypeArgs, false, d);
if (d is ClassDecl) {
ResolveClassMemberBodies((ClassDecl)d);
} else {
DatatypeDecl dtd = (DatatypeDecl)d;
if (datatypeDependencies.GetSCCRepresentative(dtd) == dtd) {
// do the following check once per SCC, so call it on each SCC representative
SccStratosphereCheck(dtd, datatypeDependencies);
}
}
allTypeParameters.PopMarker();
}
}
ClassDecl currentClass;
Function currentFunction;
readonly Scope<TypeParameter>! allTypeParameters = new Scope<TypeParameter>();
readonly Scope<IVariable>! scope = new Scope<IVariable>();
readonly Scope<Statement>! labeledStatements = new Scope<Statement>();
/// <summary>
/// Assumes type parameters have already been pushed
/// </summary>
void ResolveClassMemberTypes(ClassDecl! cl)
requires currentClass == null;
ensures currentClass == null;
{
currentClass = cl;
foreach (MemberDecl member in cl.Members) {
member.EnclosingClass = cl;
if (member is Field) {
ResolveType(((Field)member).Type);
} else if (member is Function) {
Function f = (Function)member;
allTypeParameters.PushMarker();
ResolveTypeParameters(f.TypeArgs, true, f);
ResolveFunctionSignature(f);
allTypeParameters.PopMarker();
} else if (member is Method) {
Method m = (Method)member;
allTypeParameters.PushMarker();
ResolveTypeParameters(m.TypeArgs, true, m);
ResolveMethodSignature(m);
allTypeParameters.PopMarker();
} else if (member is CouplingInvariant) {
CouplingInvariant inv = (CouplingInvariant)member;
if (currentClass is ClassRefinementDecl) {
ClassDecl refined = ((ClassRefinementDecl)currentClass).Refined;
assert refined != null;
assert classMembers.ContainsKey(refined);
Dictionary<string!,MemberDecl!> members = classMembers[refined];
// resolve abstracted fields in the refined class
List<Field!> fields = new List<Field!>();
foreach (IToken tok in inv.Toks) {
if (!members.ContainsKey(tok.val))
Error(tok, "Refined class does not declare a field: {0}", tok.val);
else {
MemberDecl! field = members[tok.val];
if (!(field is Field))
Error(tok, "Coupling invariant refers to a non-field member: {0}", tok.val);
else if (fields.Contains((Field!)field))
Error(tok, "Duplicate reference to a field in the refined class: {0}", tok.val);
else
fields.Add((Field!)field);
}
}
inv.Refined = fields;
} else {
Error(member, "Coupling invariants can only be declared in refinement classes");
}
} else {
assert false; // unexpected member type
}
if (currentClass is ClassRefinementDecl) {
ClassDecl refined = ((ClassRefinementDecl)currentClass).Refined;
assert refined != null;
assert classMembers.ContainsKey(refined);
// there is a member with the same name in refined class if and only if the member is a refined method
if ((member is MethodRefinement) != (classMembers[refined].ContainsKey(member.Name)))
Error(member, "Refined class has a member with the same name as in the refinement class: {0}", member.Name);
}
}
currentClass = null;
}
/// <summary>
/// Assumes type parameters have already been pushed, and that all types in class members have been resolved
/// </summary>
void ResolveClassMemberBodies(ClassDecl! cl)
requires currentClass == null;
ensures currentClass == null;
{
ResolveAttributes(cl.Attributes, false);
currentClass = cl;
foreach (MemberDecl member in cl.Members) {
ResolveAttributes(member.Attributes, false);
if (member is Field) {
// nothing more to do
} else if (member is Function) {
Function f = (Function)member;
allTypeParameters.PushMarker();
ResolveTypeParameters(f.TypeArgs, false, f);
ResolveFunction(f);
allTypeParameters.PopMarker();
} else if (member is Method) {
Method m = (Method)member;
allTypeParameters.PushMarker();
ResolveTypeParameters(m.TypeArgs, false, m);
ResolveMethod(m);
allTypeParameters.PopMarker();
// check if signature of the refined method matches the refinement method
if (member is MethodRefinement) {
MethodRefinement mf = (MethodRefinement)member;
assert currentClass is ClassRefinementDecl;
assert ((ClassRefinementDecl)currentClass).Refined != null; // should have already been resolved
MemberDecl d = classMembers[((ClassRefinementDecl)currentClass).Refined][mf.Name];
if (d is Method) {
mf.Refined = (Method)d;
if (mf.Ins.Count != mf.Refined.Ins.Count)
Error(mf, "Different number of input variables");
if (mf.Outs.Count != mf.Refined.Outs.Count)
Error(mf, "Different number of output variables");
if (mf.IsStatic || mf.Refined.IsStatic)
Error(mf, "Refined methods cannot be static");
} else {
Error(member, "Refined class has a non-method member with the same name: {0}", member.Name);
}
}
} else if (member is CouplingInvariant) {
CouplingInvariant inv = (CouplingInvariant)member;
assert inv.Refined != null;
inv.Formals = new List<Formal!>();
scope.PushMarker();
for (int i = 0; i < inv.Refined.Count; i++) {
Field! field = inv.Refined[i];
Formal! formal = new Formal(inv.Toks[i], field.Name, field.Type, true, field.IsGhost);
inv.Formals.Add(formal);
scope.Push(inv.Toks[i].val, formal);
}
ResolveExpression(inv.Expr, false, true);
scope.PopMarker();
} else {
assert false; // unexpected member type
}
}
currentClass = null;
}
/// <summary>
/// Assumes type parameters have already been pushed
/// </summary>
void ResolveCtorTypes(DatatypeDecl! dt, Graph<DatatypeDecl!>! dependencies)
{
foreach (DatatypeCtor ctor in dt.Ctors) {
ctor.EnclosingDatatype = dt;
allTypeParameters.PushMarker();
ResolveTypeParameters(ctor.TypeArgs, true, ctor);
ResolveCtorSignature(ctor);
allTypeParameters.PopMarker();
foreach (Formal p in ctor.Formals) {
DatatypeDecl dependee = p.Type.AsDatatype;
if (dependee != null) {
dependencies.AddEdge(dt, dependee);
}
}
}
}
/// <summary>
/// Check that the SCC of 'startingPoint' can be carved up into stratospheres in such a way that each
/// datatype has some value that can be constructed from datatypes in lower stratospheres only.
/// The algorithm used here is quadratic in the number of datatypes in the SCC. Since that number is
/// deemed to be rather small, this seems okay.
/// </summary>
void SccStratosphereCheck(DatatypeDecl! startingPoint, Graph<DatatypeDecl!>! dependencies)
{
List<DatatypeDecl!> scc = dependencies.GetSCC(startingPoint);
List<DatatypeDecl!>! cleared = new List<DatatypeDecl!>(); // this is really a set
while (true) {
int clearedThisRound = 0;
foreach (DatatypeDecl dt in scc) {
if (cleared.Contains(dt)) {
// previously cleared
} else if (StratosphereCheck(dt, dependencies, cleared)) {
clearedThisRound++;
cleared.Add(dt);
// (it would be nice if the List API allowed us to remove 'dt' from 'scc' here; then we wouldn't have to check 'cleared.Contains(dt)' above and below)
}
}
if (cleared.Count == scc.Count) {
// all is good
return;
} else if (clearedThisRound != 0) {
// some progress was made, so let's keep going
} else {
// whatever is in scc-cleared now failed to pass the test
foreach (DatatypeDecl dt in scc) {
if (!cleared.Contains(dt)) {
Error(dt, "because of cyclic dependencies among constructor argument types, no instances of datatype '{0}' can be constructed", dt.Name);
}
}
return;
}
}
}
/// <summary>
/// Check that the datatype has some constructor all whose argument types go to a lower stratum, which means
/// go to a different SCC or to a type in 'goodOnes'.
/// Returns 'true' and sets dt.DefaultCtor if that is the case.
/// </summary>
bool StratosphereCheck(DatatypeDecl! dt, Graph<DatatypeDecl!>! dependencies, List<DatatypeDecl!>! goodOnes) {
// Stated differently, check that there is some constuctor where no argument type goes to the same stratum.
DatatypeDecl stratumRepresentative = dependencies.GetSCCRepresentative(dt);
foreach (DatatypeCtor ctor in dt.Ctors) {
foreach (Formal p in ctor.Formals) {
DatatypeDecl dependee = p.Type.AsDatatype;
if (dependee == null) {
// the type is not a datatype, which means it's in the lowest stratum (below all datatypes)
} else if (dependencies.GetSCCRepresentative(dependee) != stratumRepresentative) {
// the argument type goes to a different stratum, which must be a "lower" one, so this argument is fine
} else if (goodOnes.Contains(dependee)) {
// the argument type is in the same SCC, but has already passed the test, so it is to be considered as
// being in a lower stratum
} else {
// the argument type is in the same stratum as 'dt', so this constructor is not what we're looking for
goto NEXT_OUTER_ITERATION;
}
}
// this constructor satisfies the requirements, so the datatype is allowed
dt.DefaultCtor = ctor;
return true;
NEXT_OUTER_ITERATION: {}
}
// no constructor satisfied the requirements, so this is an illegal datatype declaration
return false;
}
void ResolveAttributes(Attributes attrs, bool twoState) {
// order does not matter for resolution, so resolve them in reverse order
for (; attrs != null; attrs = attrs.Prev) {
ResolveAttributeArgs(attrs.Args, twoState, true);
}
}
void ResolveAttributeArgs(List<Attributes.Argument!>! args, bool twoState, bool specContext) {
foreach (Attributes.Argument aa in args) {
if (aa.E != null) {
ResolveExpression(aa.E, twoState, specContext);
}
}
}
void ResolveTriggers(Triggers trigs, bool twoState) {
// order does not matter for resolution, so resolve them in reverse order
for (; trigs != null; trigs = trigs.Prev) {
foreach (Expression e in trigs.Terms) {
ResolveExpression(e, twoState, true);
}
}
}
void ResolveTypeParameters(List<TypeParameter!>! tparams, bool emitErrors, TypeParameter.ParentType! parent) {
// push non-duplicated type parameter names
foreach (TypeParameter tp in tparams) {
if (emitErrors) {
// we're seeing this TypeParameter for the first time
tp.Parent = parent;
}
if (!allTypeParameters.Push(tp.Name, tp) && emitErrors) {
Error(tp, "Duplicate type-parameter name: {0}", tp.Name);
}
}
}
/// <summary>
/// Assumes type parameters have already been pushed
/// </summary>
void ResolveFunctionSignature(Function! f) {
scope.PushMarker();
foreach (Formal p in f.Formals) {
if (!scope.Push(p.Name, p)) {
Error(p, "Duplicate parameter name: {0}", p.Name);
}
ResolveType(p.Type);
}
ResolveType(f.ResultType);
scope.PopMarker();
}
/// <summary>
/// Assumes type parameters have already been pushed
/// </summary>
void ResolveFunction(Function! f)
requires currentFunction == null;
ensures currentFunction == null;
{
scope.PushMarker();
currentFunction = f;
if (f.IsStatic) {
scope.AllowInstance = false;
}
foreach (Formal p in f.Formals) {
scope.Push(p.Name, p);
}
foreach (Expression r in f.Req) {
ResolveExpression(r, false, true);
assert r.Type != null; // follows from postcondition of ResolveExpression
if (!UnifyTypes(r.Type, Type.Bool)) {
Error(r, "Precondition must be a boolean (got {0})", r.Type);
}
}
foreach (FrameExpression fr in f.Reads) {
ResolveFrameExpression(fr, "reads");
}
foreach (Expression r in f.Decreases) {
ResolveExpression(r, false, true);
// any type is fine
}
if (f.Body != null) {
ResolveExpression(f.Body, false, f.IsGhost);
assert f.Body.Type != null; // follows from postcondition of ResolveExpression
if (!UnifyTypes(f.Body.Type, f.ResultType)) {
Error(f, "Function body type mismatch (expected {0}, got {1})", f.ResultType, f.Body.Type);
}
}
currentFunction = null;
scope.PopMarker();
}
void ResolveFrameExpression(FrameExpression! fe, string! kind) {
ResolveExpression(fe.E, false, true);
Type t = fe.E.Type;
assert t != null; // follows from postcondition of ResolveExpression
if (t is CollectionType) {
t = ((CollectionType)t).Arg;
}
if (t is ObjectType) {
// fine, as long as there's no field name
if (fe.FieldName != null) {
Error(fe.E, "type '{0}' does not contain a field named '{1}'", t, fe.FieldName);
}
} else if (UserDefinedType.DenotesClass(t) != null) {
// fine type
if (fe.FieldName != null) {
UserDefinedType ctype;
MemberDecl member = ResolveMember(fe.E.tok, t, fe.FieldName, out ctype);
if (member == null) {
// error has already been reported by ResolveMember
} else if (!(member is Field)) {
Error(fe.E, "member {0} in class {1} does not refer to a field", fe.FieldName, ((!)ctype).Name);
} else {
assert ctype != null && ctype.ResolvedClass != null; // follows from postcondition of ResolveMember
fe.Field = (Field)member;
}
}
} else {
Error(fe.E, "a {0}-clause expression must denote an object or a collection of objects (instead got {1})", kind, fe.E.Type);
}
}
/// <summary>
/// Assumes type parameters have already been pushed
/// </summary>
void ResolveMethodSignature(Method! m) {
scope.PushMarker();
// resolve in-parameters
foreach (Formal p in m.Ins) {
if (!scope.Push(p.Name, p)) {
Error(p, "Duplicate parameter name: {0}", p.Name);
}
ResolveType(p.Type);
}
// resolve out-parameters
foreach (Formal p in m.Outs) {
if (!scope.Push(p.Name, p)) {
Error(p, "Duplicate parameter name: {0}", p.Name);
}
ResolveType(p.Type);
}
scope.PopMarker();
}
/// <summary>
/// Assumes type parameters have already been pushed
/// </summary>
void ResolveMethod(Method! m) {
// Add in-parameters to the scope, but don't care about any duplication errors, since they have already been reported
scope.PushMarker();
if (m.IsStatic) {
scope.AllowInstance = false;
}
foreach (Formal p in m.Ins) {
scope.Push(p.Name, p);
}
// Start resolving specification...
foreach (MaybeFreeExpression e in m.Req) {
ResolveExpression(e.E, false, true);
assert e.E.Type != null; // follows from postcondition of ResolveExpression
if (!UnifyTypes(e.E.Type, Type.Bool)) {
Error(e.E, "Precondition must be a boolean (got {0})", e.E.Type);
}
}
foreach (FrameExpression fe in m.Mod) {
ResolveFrameExpression(fe, "modifies");
}
foreach (Expression e in m.Decreases) {
ResolveExpression(e, false, true);
// any type is fine
}
// Add out-parameters to the scope, but don't care about any duplication errors, since they have already been reported
foreach (Formal p in m.Outs) {
scope.Push(p.Name, p);
}
// ... continue resolving specification
foreach (MaybeFreeExpression e in m.Ens) {
ResolveExpression(e.E, true, true);
assert e.E.Type != null; // follows from postcondition of ResolveExpression
if (!UnifyTypes(e.E.Type, Type.Bool)) {
Error(e.E, "Postcondition must be a boolean (got {0})", e.E.Type);
}
}
// Resolve body
if (m.Body != null) {
ResolveStatement(m.Body, m.IsGhost, m);
}
scope.PopMarker();
}
/// <summary>
/// Assumes type parameters have already been pushed
/// </summary>
void ResolveCtorSignature(DatatypeCtor! ctor) {
scope.PushMarker();
foreach (Formal p in ctor.Formals) {
if (!scope.Push(p.Name, p)) {
Error(p, "Duplicate parameter name: {0}", p.Name);
}
ResolveType(p.Type);
}
scope.PopMarker();
}
public void ResolveType(Type! type) {
if (type is BasicType) {
// nothing to resolve
} else if (type is CollectionType) {
ResolveType(((CollectionType)type).Arg);
} else if (type is UserDefinedType) {
UserDefinedType t = (UserDefinedType)type;
foreach (Type tt in t.TypeArgs) {
ResolveType(tt);
}
TypeParameter tp = allTypeParameters.Find(t.Name);
if (tp != null) {
if (t.TypeArgs.Count == 0) {
t.ResolvedParam = tp;
} else {
Error(t.tok, "Type parameter expects no type arguments: {0}", t.Name);
}
} else if (t.ResolvedClass == null) { // this test is becausee 'array' is already resolved; TODO: an alternative would be to pre-populate 'classes' with built-in references types like 'array' (and perhaps in the future 'string')
TopLevelDecl d;
if (!classes.TryGetValue(t.Name, out d)) {
Error(t.tok, "Undeclared top-level type or type parameter: {0}", t.Name);
} else if (((!)d).TypeArgs.Count == t.TypeArgs.Count) {
t.ResolvedClass = d;
} else {
Error(t.tok, "Wrong number of type arguments ({0} instead of {1}) passed to class/datatype: {2}", t.TypeArgs.Count, d.TypeArgs.Count, t.Name);
}
}
} else if (type is TypeProxy) {
TypeProxy t = (TypeProxy)type;
if (t.T != null) {
ResolveType(t.T);
}
} else {
assert false; // unexpected type
}
}
public bool UnifyTypes(Type! a, Type! b) {
while (a is TypeProxy) {
TypeProxy proxy = (TypeProxy)a;
if (proxy.T == null) {
// merge a and b; to avoid cycles, first get to the bottom of b
while (b is TypeProxy && ((TypeProxy)b).T != null) {
b = ((TypeProxy)b).T;
}
return AssignProxy(proxy, b);
} else {
a = proxy.T;
}
}
while (b is TypeProxy) {
TypeProxy proxy = (TypeProxy)b;
if (proxy.T == null) {
// merge a and b (we have already got to the bottom of a)
return AssignProxy(proxy, a);
} else {
b = proxy.T;
}
}
#if !NO_CHEAP_OBJECT_WORKAROUND
if (a is ObjectType || b is ObjectType) { // TODO: remove this temporary hack
// allow anything with object; this is BOGUS
return true;
}
#endif
// Now, a and b are non-proxies and stand for the same things as the original a and b, respectively.
if (a is BoolType) {
return b is BoolType;
} else if (a is IntType) {
return b is IntType;
} else if (a is ObjectType) {
return b is ObjectType;
} else if (a is SetType) {
return b is SetType && UnifyTypes(((SetType)a).Arg, ((SetType)b).Arg);
} else if (a is SeqType) {
return b is SeqType && UnifyTypes(((SeqType)a).Arg, ((SeqType)b).Arg);
} else if (a is UserDefinedType) {
if (!(b is UserDefinedType)) {
return false;
}
UserDefinedType aa = (UserDefinedType)a;
UserDefinedType bb = (UserDefinedType)b;
if (aa.ResolvedClass != null && aa.ResolvedClass == bb.ResolvedClass) {
// these are both resolved class/datatype types
assert aa.TypeArgs.Count == bb.TypeArgs.Count;
bool successSoFar = true;
for (int i = 0; i < aa.TypeArgs.Count; i++) {
if (!UnifyTypes(aa.TypeArgs[i], bb.TypeArgs[i])) {
successSoFar = false;
}
}
return successSoFar;
} else if (aa.ResolvedParam != null && aa.ResolvedParam == bb.ResolvedParam) {
// these are both resolved type parameters
assert aa.TypeArgs.Count == 0 && bb.TypeArgs.Count == 0;
return true;
} else {
// something is wrong; either aa or bb wasn't properly resolved, or they don't unify
return false;
}
} else {
assert false; // unexpected type
}
}
bool AssignProxy(TypeProxy! proxy, Type! t)
requires proxy.T == null;
requires t is TypeProxy ==> ((TypeProxy)t).T == null;
modifies proxy.T, ((TypeProxy)t).T; // might also change t.T if t is a proxy
ensures result ==> proxy == t || proxy.T != null || (t is TypeProxy && ((TypeProxy)t).T != null);
{
if (proxy == t) {
// they are already in the same equivalence class
return true;
} else if (proxy is UnrestrictedTypeProxy) {
// it's fine to redirect proxy to t (done below)
} else if (t is UnrestrictedTypeProxy) {
// merge proxy and t by redirecting t to proxy, rather than the other way around
((TypeProxy)t).T = proxy;
return true;
} else if (t is RestrictedTypeProxy) {
// Both proxy and t are restricted type proxies. To simplify unification, order proxy and t
// according to their types.
RestrictedTypeProxy r0 = (RestrictedTypeProxy)proxy;
RestrictedTypeProxy r1 = (RestrictedTypeProxy)t;
if (r0.OrderID <= r1.OrderID) {
return AssignRestrictedProxies(r0, r1);
} else {
return AssignRestrictedProxies(r1, r0);
}
// In the remaining cases, proxy is a restricted proxy and t is a non-proxy
} else if (proxy is DatatypeProxy) {
if (t.IsDatatype) {
// all is fine, proxy can be redirected to t
} else {
return false;
}
} else if (proxy is ObjectTypeProxy) {
if (t is ObjectType || UserDefinedType.DenotesClass(t) != null) {
// all is fine, proxy can be redirected to t
} else {
return false;
}
} else if (proxy is ObjectsTypeProxy) {
if (t is ObjectType || UserDefinedType.DenotesClass(t) != null) {
// all is good
} else if (t is CollectionType) {
proxy.T = new CollectionTypeProxy(new ObjectTypeProxy());
return UnifyTypes(proxy.T, t);
}
} else if (proxy is CollectionTypeProxy) {
CollectionTypeProxy collProxy = (CollectionTypeProxy)proxy;
if (t is CollectionType) {
if (!UnifyTypes(collProxy.Arg, ((CollectionType)t).Arg)) {
return false;
}
} else {
return false;
}
} else if (proxy is OperationTypeProxy) {
OperationTypeProxy opProxy = (OperationTypeProxy)proxy;
if (t is IntType || t is SetType || (opProxy.AllowSeq && t is SeqType)) {
// this is the expected case
} else {
return false;
}
} else if (proxy is IndexableTypeProxy) {
IndexableTypeProxy iProxy = (IndexableTypeProxy)proxy;
if (t is SeqType) {
if (!UnifyTypes(iProxy.Arg, ((SeqType)t).Arg)) {
return false;
}
} else if (t.IsArrayType) {
Type elType = UserDefinedType.ArrayElementType(t);
if (!UnifyTypes(iProxy.Arg, elType)) {
return false;
}
} else {
return false;
}
} else {
assert false; // unexpected proxy type
}
// do the merge
proxy.T = t;
return true;
}
bool AssignRestrictedProxies(RestrictedTypeProxy! a, RestrictedTypeProxy! b)
requires a != b;
requires a.T == null && b.T == null;
requires a.OrderID <= b.OrderID;
modifies a.T, b.T;
ensures result ==> a.T != null || b.T != null;
{
if (a is DatatypeProxy) {
if (b is DatatypeProxy) {
// all is fine
a.T = b;
return true;
} else {
return false;
}
} else if (a is ObjectTypeProxy) {
if (b is ObjectTypeProxy) {
// all is fine
a.T = b;
return true;
} else if (b is ObjectsTypeProxy) {
// unify a and b by redirecting b to a, since a gives the stronger requirement
b.T = a;
return true;
} else if (b is IndexableTypeProxy) {
// the intersection of ObjectTypeProxy and IndexableTypeProxy is an array type
a.T = UserDefinedType.ArrayType(Token.NoToken, ((IndexableTypeProxy)b).Arg);
b.T = a.T;
return true;
} else {
return false;
}
} else if (a is ObjectsTypeProxy) {
if (b is ObjectsTypeProxy) {
// fine
a.T = b;
return true;
} else if (b is CollectionTypeProxy) {
// fine provided b's collection-element-type can be unified with object or a class type
a.T = b;
return UnifyTypes(((CollectionTypeProxy)b).Arg, new ObjectTypeProxy());
} else if (b is OperationTypeProxy) {
// fine; restrict a to sets of object/class, and restrict b to set/seq of object/class
if (((OperationTypeProxy)b).AllowSeq) {
a.T = new CollectionTypeProxy(new ObjectTypeProxy());
b.T = a.T;
} else {
a.T = new SetType(new ObjectTypeProxy());
b.T = a.T;
}
return true;
} else if (b is IndexableTypeProxy) {
IndexableTypeProxy pb = (IndexableTypeProxy)b;
// the intersection of ObjectsTypeProxy and IndexableTypeProxy is
// EITHER a sequence of ObjectTypeProxy OR an array of anything
// TODO: here, only the first of the two cases is supported
b.T = new SeqType(pb.Arg);
a.T = b.T;
return UnifyTypes(pb.Arg, new ObjectTypeProxy());
} else {
assert false; // unexpected restricted-proxy type
}
} else if (a is CollectionTypeProxy) {
if (b is CollectionTypeProxy) {
a.T = b;
return UnifyTypes(((CollectionTypeProxy)a).Arg, ((CollectionTypeProxy)b).Arg);
} else if (b is OperationTypeProxy) {
if (((OperationTypeProxy)b).AllowSeq) {
b.T = a; // a is a stronger constraint than b
} else {
// a says set<T>,seq<T> and b says int,set; the intersection is set<T>
a.T = new SetType(((CollectionTypeProxy)a).Arg);
b.T = a.T;
}
return true;
} else if (b is IndexableTypeProxy) {
CollectionTypeProxy pa = (CollectionTypeProxy)a;
IndexableTypeProxy pb = (IndexableTypeProxy)b;
// strengthen a and b to a sequence type
a.T = new SeqType(pa.Arg);
b.T = new SeqType(pb.Arg);
return UnifyTypes(pa.Arg, pb.Arg);
} else {
assert false; // unexpected restricted-proxy type
}
} else if (a is OperationTypeProxy) {
OperationTypeProxy pa = (OperationTypeProxy)a;
if (b is OperationTypeProxy) {
if (pa.AllowSeq ==> ((OperationTypeProxy)b).AllowSeq) {
b.T = a;
} else {
a.T = b; // b has the stronger requirement
}
return true;
} else {
IndexableTypeProxy pb = (IndexableTypeProxy)b; // cast justification: lse we have unexpected restricted-proxy type
if (pa.AllowSeq) {
// strengthen a and b to a sequence type
b.T = new SeqType(pb.Arg);
a.T = b.T;
return true;
} else {
return false;
}
}
} else if (a is IndexableTypeProxy) {
assert b is IndexableTypeProxy; // else we have unexpected restricted-proxy type
a.T = b;
return UnifyTypes(((IndexableTypeProxy)a).Arg, ((IndexableTypeProxy)b).Arg);
} else {
assert false; // unexpected restricted-proxy type
}
}
public void ResolveStatement(Statement! stmt, bool specContextOnly, Method! method)
requires !(stmt is LabelStmt); // these should be handled inside lists of statements
{
if (stmt is UseStmt) {
UseStmt s = (UseStmt)stmt;
s.IsGhost = true;
ResolveExpression(s.Expr, true, true);
assert s.Expr.Type != null; // follows from postcondition of ResolveExpression
Expression expr = s.Expr;
while (true) {
if (expr is OldExpr) {
expr = ((OldExpr)expr).E;
} else {
break;
}
}
} else if (stmt is PredicateStmt) {
PredicateStmt s = (PredicateStmt)stmt;
s.IsGhost = true;
ResolveExpression(s.Expr, true, true);
assert s.Expr.Type != null; // follows from postcondition of ResolveExpression
if (!UnifyTypes(s.Expr.Type, Type.Bool)) {
Error(s.Expr, "condition is expected to be of type {0}, but is {1}", Type.Bool, s.Expr.Type);
}
} else if (stmt is PrintStmt) {
PrintStmt s = (PrintStmt)stmt;
ResolveAttributeArgs(s.Args, false, false);
} else if (stmt is BreakStmt) {
BreakStmt s = (BreakStmt)stmt;
if (s.TargetLabel != null) {
Statement target = labeledStatements.Find(s.TargetLabel);
if (target == null) {
Error(s, "break label is undefined or not in scope: {0}", s.TargetLabel);
} else {
s.TargetStmt = target;
}
}
} else if (stmt is ReturnStmt) {
// nothing to resolve
} else if (stmt is AssignStmt) {
AssignStmt s = (AssignStmt)stmt;
int prevErrorCount = ErrorCount;
if (s.Lhs is SeqSelectExpr) {
ResolveSeqSelectExpr((SeqSelectExpr)s.Lhs, true, false, true);
} else {
ResolveExpression(s.Lhs, true, true); // allow ghosts for now, but see FieldSelectExpr LHS case below
}
bool lhsResolvedSuccessfully = ErrorCount == prevErrorCount;
assert s.Lhs.Type != null; // follows from postcondition of ResolveExpression
// check that LHS denotes a mutable variable or a field
bool lvalueIsGhost = false;
if (s.Lhs is IdentifierExpr) {
IVariable var = ((IdentifierExpr)s.Lhs).Var;
if (var == null) {
// the LHS didn't resolve correctly; some error would already have been reported
} else {
lvalueIsGhost = var.IsGhost;
if (!var.IsMutable) {
Error(stmt, "LHS of assignment must denote a mutable variable or field");
}
}
} else if (s.Lhs is FieldSelectExpr) {
// LHS is fine, but restrict the RHS to ExprRhs
if (!(s.Rhs is ExprRhs)) {
Error(stmt, "Assignment to field must have an expression RHS; try using a temporary local variable");
} else {
FieldSelectExpr fse = (FieldSelectExpr)s.Lhs;
if (fse.Field != null) { // otherwise, an error was reported above
lvalueIsGhost = fse.Field.IsGhost;
if (!lvalueIsGhost) {
if (specContextOnly) {
Error(stmt, "Assignment to non-ghost field is not allowed in this context (because this is a ghost method or because the statement is guarded by a specification-only expression)");
} else {
// It is now that we wish we would have resolved s.Lhs to not allow ghosts. Too late, so we do
// the next best thing.
if (lhsResolvedSuccessfully && UsesSpecFeatures(fse.Obj)) {
Error(stmt, "Assignment to non-ghost field is not allowed to use specification-only expressions in the receiver");
}
}
}
}
}
} else if (s.Lhs is SeqSelectExpr) {
SeqSelectExpr lhs = (SeqSelectExpr)s.Lhs;
// LHS is fine, provided the "sequence" is really an array
if (lhsResolvedSuccessfully) {
assert lhs.Seq.Type != null;
Type elementType = new InferredTypeProxy();
if (!UnifyTypes(lhs.Seq.Type, UserDefinedType.ArrayType(Token.NoToken, elementType))) {
Error(lhs.Seq, "LHS of array assignment must denote an array element (found {0})", lhs.Seq.Type);
}
if (specContextOnly) {
Error(stmt, "Assignment to array element is not allowed in this context (because this is a ghost method or because the statement is guarded by a specification-only expression)");
}
}
if (!(s.Rhs is ExprRhs)) {
Error(stmt, "Assignment to array element must have an expression RHS; try using a temporary local variable");
}
} else {
Error(stmt, "LHS of assignment must denote a mutable variable or field");
}
s.IsGhost = lvalueIsGhost;
if (s.Rhs is ExprRhs) {
ExprRhs rr = (ExprRhs)s.Rhs;
ResolveExpression(rr.Expr, true, lvalueIsGhost);
assert rr.Expr.Type != null; // follows from postcondition of ResolveExpression
Type lhsType = s.Lhs.Type;
if (s.Lhs is SeqSelectExpr && !((SeqSelectExpr)s.Lhs).SelectOne) {
assert lhsType.IsArrayType;
lhsType = UserDefinedType.ArrayElementType(lhsType);
}
if (!UnifyTypes(lhsType, rr.Expr.Type)) {
Error(stmt, "RHS (of type {0}) not assignable to LHS (of type {1})", rr.Expr.Type, s.Lhs.Type);
}
} else if (s.Rhs is TypeRhs) {
TypeRhs rr = (TypeRhs)s.Rhs;
Type t = ResolveTypeRhs(rr, stmt, lvalueIsGhost);
if (!UnifyTypes(s.Lhs.Type, t)) {
Error(stmt, "type {0} is not assignable to LHS (of type {1})", t, s.Lhs.Type);
}
} else if (s.Rhs is HavocRhs) {
// nothing else to do
} else {
assert false; // unexpected RHS
}
} else if (stmt is VarDecl) {
VarDecl s = (VarDecl)stmt;
if (s.OptionalType != null) {
ResolveType(s.OptionalType);
s.type = s.OptionalType;
}
if (s.Rhs != null) {
Type! rhsType;
if (s.Rhs is ExprRhs) {
ExprRhs rr = (ExprRhs)s.Rhs;
ResolveExpression(rr.Expr, true, s.IsGhost);
assert rr.Expr.Type != null; // follows from postcondition of ResolveExpression
rhsType = rr.Expr.Type;
} else if (s.Rhs is TypeRhs) {
TypeRhs rr = (TypeRhs)s.Rhs;
rhsType = ResolveTypeRhs(rr, stmt, s.IsGhost);
} else {
assert false; // unexpected RHS
}
if (s.OptionalType == null) {
s.type = rhsType;
} else if (!UnifyTypes(s.OptionalType, rhsType)) {
Error(stmt, "initialization RHS (of type {0}) not assignable to variable (of type {1})", rhsType, s.OptionalType);
}
}
// now that the declaration has been processed, add the name to the scope
if (!scope.Push(s.Name, s)) {
Error(s, "Duplicate local-variable name: {0}", s.Name);
}
} else if (stmt is CallStmt) {
CallStmt s = (CallStmt)stmt;
// resolve receiver
ResolveReceiver(s.Receiver, true, false);
assert s.Receiver.Type != null; // follows from postcondition of ResolveExpression
// resolve the method name
UserDefinedType ctype;
MemberDecl member = ResolveMember(s.Tok, s.Receiver.Type, s.MethodName, out ctype);
Method callee = null;
if (member == null) {
// error has already been reported by ResolveMember
} else if (!(member is Method)) {
Error(s, "member {0} in class {1} does not refer to a method", s.MethodName, ((!)ctype).Name);
} else {
callee = (Method)member;
s.Method = callee;
s.IsGhost = callee.IsGhost;
if (specContextOnly && !callee.IsGhost) {
Error(s, "only ghost methods can be called from this context");
}
}
// resolve any local variables declared here
foreach (AutoVarDecl local in s.NewVars) {
// first, fix up the local variables to be ghost variable if the corresponding formal out-parameter is a ghost
if (s.IsGhost || callee != null && local.Index < callee.Outs.Count && callee.Outs[local.Index].IsGhost) {
local.MakeGhost();
}
ResolveStatement(local, specContextOnly, method);
}
// resolve left-hand side
Dictionary<string!,object> lhsNameSet = new Dictionary<string!,object>();
foreach (IdentifierExpr lhs in s.Lhs) {
ResolveExpression(lhs, true, true);
if (lhsNameSet.ContainsKey(lhs.Name)) {
Error(s, "Duplicate variable in left-hand side of call statement: {0}", lhs.Name);
} else {
lhsNameSet.Add(lhs.Name, null);
}
}
// resolve arguments
int j = 0;
foreach (Expression e in s.Args) {
bool allowGhost = s.IsGhost || callee == null || callee.Ins.Count <= j || callee.Ins[j].IsGhost;
ResolveExpression(e, true, allowGhost);
j++;
}
if (callee == null) {
// error has been reported above
} else if (callee.Ins.Count != s.Args.Count) {
Error(s, "wrong number of method arguments (got {0}, expected {1})", s.Args.Count, callee.Ins.Count);
} else if (callee.Outs.Count != s.Lhs.Count) {
Error(s, "wrong number of method result arguments (got {0}, expected {1})", s.Lhs.Count, callee.Outs.Count);
} else {
assert ctype != null; // follows from postcondition of ResolveMember above
if (!scope.AllowInstance && !callee.IsStatic && s.Receiver is ThisExpr) {
// The call really needs an instance, but that instance is given as 'this', which is not
// available in this context. For more details, see comment in the resolution of a
// FunctionCallExpr.
Error(s.Receiver, "'this' is not allowed in a 'static' context");
}
// build the type substitution map
Dictionary<TypeParameter!,Type!> subst = new Dictionary<TypeParameter!,Type!>();
for (int i = 0; i < ctype.TypeArgs.Count; i++) {
subst.Add(((!)ctype.ResolvedClass).TypeArgs[i], ctype.TypeArgs[i]);
}
foreach (TypeParameter p in callee.TypeArgs) {
subst.Add(p, new ParamTypeProxy(p));
}
// type check the arguments
for (int i = 0; i < callee.Ins.Count; i++) {
Type st = SubstType(callee.Ins[i].Type, subst);
if (!UnifyTypes((!)s.Args[i].Type, st)) {
Error(s, "incorrect type of method in-parameter {0} (expected {1}, got {2})", i, st, s.Args[i].Type);
}
}
for (int i = 0; i < callee.Outs.Count; i++) {
Type st = SubstType(callee.Outs[i].Type, subst);
IdentifierExpr lhs = s.Lhs[i];
if (!UnifyTypes((!)lhs.Type, st)) {
Error(s, "incorrect type of method out-parameter {0} (expected {1}, got {2})", i, st, lhs.Type);
} else if (!specContextOnly && !((!)lhs.Var).IsGhost && (s.IsGhost || callee.Outs[i].IsGhost)) {
Error(s, "actual out-parameter {0} is required to be a ghost variable", i);
}
}
// Resolution termination check
if (method.EnclosingClass != null && callee.EnclosingClass != null) {
ModuleDecl callerModule = method.EnclosingClass.Module;
ModuleDecl calleeModule = callee.EnclosingClass.Module;
if (callerModule == calleeModule) {
// intra-module call; this is allowed; add edge in module's call graph
callerModule.CallGraph.AddEdge(method, callee);
} else if (calleeModule.IsDefaultModule) {
// all is fine: everything implicitly imports the default module
} else if (importGraph.Reaches(callerModule, calleeModule)) {
// all is fine: the callee is downstream of the caller
} else {
Error(s, "inter-module calls must follow the module import relation (so module {0} must transitively import {1})", callerModule.Name, calleeModule.Name);
}
}
}
} else if (stmt is BlockStmt) {
scope.PushMarker();
int labelsToPop = 0;
foreach (Statement ss in ((BlockStmt)stmt).Body) {
if (ss is LabelStmt) {
LabelStmt ls = (LabelStmt)ss;
labeledStatements.PushMarker();
bool b = labeledStatements.Push(ls.Label, ls);
assert b; // since we just pushed a marker, we expect the Push to succeed
labelsToPop++;
} else {
ResolveStatement(ss, specContextOnly, method);
for (; 0 < labelsToPop; labelsToPop--) { labeledStatements.PopMarker(); }
}
}
for (; 0 < labelsToPop; labelsToPop--) { labeledStatements.PopMarker(); }
scope.PopMarker();
} else if (stmt is IfStmt) {
IfStmt s = (IfStmt)stmt;
bool branchesAreSpecOnly = specContextOnly;
if (s.Guard != null) {
int prevErrorCount = ErrorCount;
ResolveExpression(s.Guard, true, true);
assert s.Guard.Type != null; // follows from postcondition of ResolveExpression
bool successfullyResolved = ErrorCount == prevErrorCount;
if (!UnifyTypes(s.Guard.Type, Type.Bool)) {
Error(s.Guard, "condition is expected to be of type {0}, but is {1}", Type.Bool, s.Guard.Type);
}
if (!specContextOnly && successfullyResolved) {
branchesAreSpecOnly = UsesSpecFeatures(s.Guard);
}
}
s.IsGhost = branchesAreSpecOnly;
ResolveStatement(s.Thn, branchesAreSpecOnly, method);
if (s.Els != null) {
ResolveStatement(s.Els, branchesAreSpecOnly, method);
}
} else if (stmt is WhileStmt) {
WhileStmt s = (WhileStmt)stmt;
bool bodyIsSpecOnly = specContextOnly;
if (s.Guard != null) {
int prevErrorCount = ErrorCount;
ResolveExpression(s.Guard, true, true);
assert s.Guard.Type != null; // follows from postcondition of ResolveExpression
bool successfullyResolved = ErrorCount == prevErrorCount;
if (!UnifyTypes(s.Guard.Type, Type.Bool)) {
Error(s.Guard, "condition is expected to be of type {0}, but is {1}", Type.Bool, s.Guard.Type);
}
if (!specContextOnly && successfullyResolved) {
bodyIsSpecOnly = UsesSpecFeatures(s.Guard);
}
}
foreach (MaybeFreeExpression inv in s.Invariants) {
ResolveExpression(inv.E, true, true);
assert inv.E.Type != null; // follows from postcondition of ResolveExpression
if (!UnifyTypes(inv.E.Type, Type.Bool)) {
Error(inv.E, "invariant is expected to be of type {0}, but is {1}", Type.Bool, inv.E.Type);
}
}
foreach (Expression e in s.Decreases) {
ResolveExpression(e, true, true);
// any type is fine
}
s.IsGhost = bodyIsSpecOnly;
ResolveStatement(s.Body, bodyIsSpecOnly, method);
} else if (stmt is ForeachStmt) {
ForeachStmt s = (ForeachStmt)stmt;
ResolveExpression(s.Collection, true, true);
assert s.Collection.Type != null; // follows from postcondition of ResolveExpression
if (!UnifyTypes(s.Collection.Type, new CollectionTypeProxy(s.BoundVar.Type))) {
Error(s.Collection, "The type is expected to be a collection of {0} (instead got {1})", s.BoundVar.Type, s.Collection.Type);
}
scope.PushMarker();
bool b = scope.Push(s.BoundVar.Name, s.BoundVar);
assert b; // since we just pushed a marker, we expect the Push to succeed
ResolveType(s.BoundVar.Type);
int prevErrorCount = ErrorCount;
ResolveExpression(s.Range, true, true);
assert s.Range.Type != null; // follows from postcondition of ResolveExpression
if (!UnifyTypes(s.Range.Type, Type.Bool)) {
Error(s.Range, "range condition is expected to be of type {0}, but is {1}", Type.Bool, s.Range.Type);
}
bool successfullyResolvedCollectionAndRange = ErrorCount == prevErrorCount;
foreach (PredicateStmt ss in s.BodyPrefix) {
ResolveStatement(ss, specContextOnly, method);
}
bool specOnly = specContextOnly ||
(successfullyResolvedCollectionAndRange && (UsesSpecFeatures(s.Collection) || UsesSpecFeatures(s.Range)));
s.IsGhost = specOnly;
ResolveStatement(s.BodyAssign, specOnly, method);
// check for correct usage of BoundVar in LHS and RHS of this assignment
FieldSelectExpr lhs = s.BodyAssign.Lhs as FieldSelectExpr;
IdentifierExpr obj = lhs == null ? null : lhs.Obj as IdentifierExpr;
if (obj != null && obj.Var == s.BoundVar) {
// exemplary!
} else {
Error(s, "assignment inside foreach must assign to a field of the bound variable of the foreach statement");
}
scope.PopMarker();
} else if (stmt is MatchStmt) {
MatchStmt s = (MatchStmt)stmt;
bool bodyIsSpecOnly = specContextOnly;
int prevErrorCount = ErrorCount;
ResolveExpression(s.Source, true, true);
assert s.Source.Type != null; // follows from postcondition of ResolveExpression
bool successfullyResolved = ErrorCount == prevErrorCount;
if (!specContextOnly && successfullyResolved) {
bodyIsSpecOnly = UsesSpecFeatures(s.Source);
}
UserDefinedType sourceType = null;
DatatypeDecl dtd = null;
Dictionary<TypeParameter!,Type!> subst = new Dictionary<TypeParameter!,Type!>();
if (s.Source.Type.IsDatatype) {
sourceType = (UserDefinedType)s.Source.Type;
dtd = (DatatypeDecl!)sourceType.ResolvedClass;
}
Dictionary<string!,DatatypeCtor!> ctors;
if (dtd == null) {
Error(s.Source, "the type of the match source expression must be a datatype");
ctors = null;
} else {
assert sourceType != null; // dtd and sourceType are set together above
ctors = datatypeCtors[dtd];
assert ctors != null; // dtd should have been inserted into datatypeCtors during a previous resolution stage
// build the type-parameter substitution map for this use of the datatype
for (int i = 0; i < dtd.TypeArgs.Count; i++) {
subst.Add(dtd.TypeArgs[i], sourceType.TypeArgs[i]);
}
}
s.IsGhost = bodyIsSpecOnly;
Dictionary<string!,object> memberNamesUsed = new Dictionary<string!,object>(); // this is really a set
foreach (MatchCaseStmt mc in s.Cases) {
DatatypeCtor ctor = null;
if (ctors != null) {
assert dtd != null;
if (!ctors.TryGetValue(mc.Id, out ctor)) {
Error(mc.tok, "member {0} does not exist in datatype {1}", mc.Id, dtd.Name);
} else {
assert ctor != null; // follows from postcondition of TryGetValue
mc.Ctor = ctor;
if (ctor.Formals.Count != mc.Arguments.Count) {
Error(mc.tok, "member {0} has wrong number of formals (found {1}, expected {2})", mc.Arguments.Count, ctor.Formals.Count);
}
if (memberNamesUsed.ContainsKey(mc.Id)) {
Error(mc.tok, "member {0} appears in more than one case", mc.Id);
} else {
memberNamesUsed.Add(mc.Id, null); // add mc.Id to the set of names used
}
}
}
scope.PushMarker();
if (ctor != null) {
// add the constructor's own type parameters to the substitution map
foreach (TypeParameter p in ctor.TypeArgs) {
subst.Add(p, new ParamTypeProxy(p));
}
}
int i = 0;
foreach (BoundVar v in mc.Arguments) {
if (!scope.Push(v.Name, v)) {
Error(v, "Duplicate parameter name: {0}", v.Name);
}
ResolveType(v.Type);
if (ctor != null && i < ctor.Formals.Count) {
Formal formal = ctor.Formals[i];
Type st = SubstType(formal.Type, subst);
if (!UnifyTypes(v.Type, st)) {
Error(stmt, "the declared type of the formal ({0}) does not agree with the corresponding type in the constructor's signature ({1})", v.Type, st);
}
v.IsGhost = formal.IsGhost;
}
i++;
}
foreach (Statement ss in mc.Body) {
ResolveStatement(ss, bodyIsSpecOnly, method);
}
scope.PopMarker();
}
if (dtd != null && memberNamesUsed.Count != dtd.Ctors.Count) {
Error(stmt, "match expression does not cover all constructors");
}
} else {
assert false;
}
}
Type! ResolveTypeRhs(TypeRhs! rr, Statement! stmt, bool specContext) {
ResolveType(rr.EType);
if (rr.ArraySize == null) {
if (!rr.EType.IsRefType) {
Error(stmt, "new can be applied only to reference types (got {0})", rr.EType);
}
} else {
ResolveExpression(rr.ArraySize, true, specContext);
if (rr.ArraySize.Type is IntType) {
// all is good
return UserDefinedType.ArrayType(stmt.Tok, rr.EType);
} else {
Error(stmt, "new must use an integer expression for the array size (got {0})", rr.ArraySize.Type);
}
}
return rr.EType;
}
MemberDecl ResolveMember(IToken! tok, Type! receiverType, string! memberName, out UserDefinedType ctype)
ensures result != null ==> ctype != null && ctype.ResolvedClass != null;
{
ctype = UserDefinedType.DenotesClass(receiverType);
if (ctype == null) {
Error(tok, "receiver (of type {0}) must be of a class type", receiverType);
} else {
assert ctype.ResolvedClass is ClassDecl; // follows from postcondition of DenotesClass
assert ctype.TypeArgs.Count == ctype.ResolvedClass.TypeArgs.Count; // follows from the fact that ctype was resolved
MemberDecl member;
if (!classMembers[(ClassDecl)ctype.ResolvedClass].TryGetValue(memberName, out member)) {
Error(tok, "member {0} does not exist in class {1}", memberName, ctype.Name);
} else {
return (!)member;
}
}
ctype = null;
return null;
}
Type! SubstType(Type! type, Dictionary<TypeParameter!,Type!>! subst) {
if (type is BasicType) {
return type;
} else if (type is CollectionType) {
CollectionType t = (CollectionType)type;
Type arg = SubstType(t.Arg, subst);
if (arg == t.Arg) {
return type;
} else if (type is SetType) {
return new SetType(arg);
} else if (type is SeqType) {
return new SeqType(arg);
} else {
assert false; // unexpected collection type
}
} else if (type is UserDefinedType) {
UserDefinedType t = (UserDefinedType)type;
if (t.ResolvedParam != null) {
assert t.TypeArgs.Count == 0;
Type s;
if (subst.TryGetValue(t.ResolvedParam, out s)) {
return (!)s;
} else {
return type;
}
} else if (t.ResolvedClass != null) {
List<Type!> newArgs = null; // allocate it lazily
for (int i = 0; i < t.TypeArgs.Count; i++) {
Type p = t.TypeArgs[i];
Type s = SubstType(p, subst);
if (s != p && newArgs == null) {
// lazily construct newArgs
newArgs = new List<Type!>();
for (int j = 0; j < i; j++) {
newArgs.Add(t.TypeArgs[j]);
}
}
if (newArgs != null) {
newArgs.Add(s);
}
}
if (newArgs == null) {
// there were no substitutions
return type;
} else {
return new UserDefinedType(t.tok, t.Name, t.ResolvedClass, newArgs);
}
} else {
// there's neither a resolved param nor a resolved class, which means the UserDefinedType wasn't
// properly resolved; just return it
return type;
}
} else if (type is TypeProxy) {
TypeProxy t = (TypeProxy)type;
if (t.T == null) {
return type;
} else {
// bypass the proxy
return SubstType(t.T, subst);
}
} else {
assert false; // unexpected type
}
}
public static UserDefinedType! GetThisType(IToken! tok, ClassDecl! cl) {
List<Type!> args = new List<Type!>();
foreach (TypeParameter tp in cl.TypeArgs) {
args.Add(new UserDefinedType(tok, tp.Name, tp));
}
return new UserDefinedType(tok, cl.Name, cl, args);
}
/// <summary>
/// "twoState" implies that "old" and "fresh" expressions are allowed
/// </summary>
void ResolveExpression(Expression! expr, bool twoState, bool specContext)
requires currentClass != null;
ensures expr.Type != null;
{
if (expr.Type != null) {
// expression has already been resovled
return;
}
// The following cases will resolve the subexpressions and will attempt to assign a type of expr. However, if errors occur
// and it cannot be determined what the type of expr is, then it is fine to leave expr.Type as null. In that case, the end
// of this method will assign proxy type to the expression, which reduces the number of error messages that are produced
// while type checking the rest of the program.
if (expr is LiteralExpr) {
LiteralExpr e = (LiteralExpr)expr;
if (e.Value == null) {
e.Type = new ObjectTypeProxy();
} else if (e.Value is BigInteger) {
e.Type = Type.Int;
} else if (e.Value is bool) {
e.Type = Type.Bool;
} else {
assert false; // unexpected literal type
}
} else if (expr is ThisExpr) {
if (!scope.AllowInstance) {
Error(expr, "'this' is not allowed in a 'class' context");
}
expr.Type = GetThisType(expr.tok, currentClass); // do this regardless of scope.AllowInstance, for better error reporting
} else if (expr is IdentifierExpr) {
IdentifierExpr e = (IdentifierExpr)expr;
e.Var = scope.Find(e.Name);
if (e.Var == null) {
Error(expr, "Identifier does not denote a local variable, parameter, or bound variable: {0}", e.Name);
} else {
expr.Type = e.Var.Type;
if (!specContext && e.Var.IsGhost) {
Error(expr, "ghost variables are allowed only in specification contexts");
}
}
} else if (expr is DatatypeValue) {
DatatypeValue dtv = (DatatypeValue)expr;
TopLevelDecl d;
if (!classes.TryGetValue(dtv.DatatypeName, out d)) {
Error(expr.tok, "Undeclared datatype: {0}", dtv.DatatypeName);
} else if (!(d is DatatypeDecl)) {
Error(expr.tok, "Expected datatype, found class: {0}", dtv.DatatypeName);
} else {
// this resolution is a little special, in that the syntax shows only the base name, not its instantiation (which is inferred)
DatatypeDecl dt = (DatatypeDecl)d;
List<Type!> gt = new List<Type!>(dt.TypeArgs.Count);
Dictionary<TypeParameter!,Type!> subst = new Dictionary<TypeParameter!,Type!>();
for (int i = 0; i < dt.TypeArgs.Count; i++) {
Type t = new InferredTypeProxy();
gt.Add(t);
dtv.InferredTypeArgs.Add(t);
subst.Add(dt.TypeArgs[i], t);
}
expr.Type = new UserDefinedType(dtv.tok, dtv.DatatypeName, gt);
ResolveType(expr.Type);
DatatypeCtor ctor;
if (!datatypeCtors[dt].TryGetValue(dtv.MemberName, out ctor)) {
Error(expr.tok, "undeclared constructor {0} in datatype {1}", dtv.MemberName, dtv.DatatypeName);
} else {
assert ctor != null; // follows from postcondition of TryGetValue
dtv.Ctor = ctor;
if (ctor.Formals.Count != dtv.Arguments.Count) {
Error(expr.tok, "wrong number of arguments to datatype constructor {0} (found {1}, expected {2})", dtv.DatatypeName, dtv.Arguments.Count, ctor.Formals.Count);
}
// add the constructor's own type parameters to the substitution map
foreach (TypeParameter p in ctor.TypeArgs) {
Type t = new ParamTypeProxy(p);
dtv.InferredTypeArgs.Add(t);
subst.Add(p, t);
}
}
int j = 0;
foreach (Expression arg in dtv.Arguments) {
Formal formal = ctor != null && j < ctor.Formals.Count ? ctor.Formals[j] : null;
ResolveExpression(arg, twoState, specContext || (formal != null && formal.IsGhost));
assert arg.Type != null; // follows from postcondition of ResolveExpression
if (formal != null) {
Type st = SubstType(formal.Type, subst);
if (!UnifyTypes(arg.Type, st)) {
Error(arg.tok, "incorrect type of datatype constructor argument (found {0}, expected {1})", arg.Type, st);
}
}
j++;
}
}
} else if (expr is DisplayExpression) {
DisplayExpression e = (DisplayExpression)expr;
Type elementType = new InferredTypeProxy();
foreach (Expression ee in e.Elements) {
ResolveExpression(ee, twoState, specContext);
assert ee.Type != null; // follows from postcondition of ResolveExpression
if (!UnifyTypes(elementType, ee.Type)) {
Error(ee, "All elements of display must be of the same type (got {0}, but type of previous elements is {1})", ee.Type, elementType);
}
}
if (expr is SetDisplayExpr) {
expr.Type = new SetType(elementType);
} else {
expr.Type = new SeqType(elementType);
}
} else if (expr is FieldSelectExpr) {
FieldSelectExpr e = (FieldSelectExpr)expr;
ResolveExpression(e.Obj, twoState, specContext);
assert e.Obj.Type != null; // follows from postcondition of ResolveExpression
UserDefinedType ctype;
MemberDecl member = ResolveMember(expr.tok, e.Obj.Type, e.FieldName, out ctype);
if (member == null) {
// error has already been reported by ResolveMember
} else if (!(member is Field)) {
Error(expr, "member {0} in class {1} does not refer to a field", e.FieldName, ((!)ctype).Name);
} else {
assert ctype != null && ctype.ResolvedClass != null; // follows from postcondition of ResolveMember
e.Field = (Field)member;
// build the type substitution map
Dictionary<TypeParameter!,Type!> subst = new Dictionary<TypeParameter!,Type!>();
for (int i = 0; i < ctype.TypeArgs.Count; i++) {
subst.Add(ctype.ResolvedClass.TypeArgs[i], ctype.TypeArgs[i]);
}
e.Type = SubstType(e.Field.Type, subst);
if (!specContext && e.Field.IsGhost) {
Error(expr, "ghost fields are allowed only in specification contexts");
}
}
} else if (expr is SeqSelectExpr) {
SeqSelectExpr e = (SeqSelectExpr)expr;
ResolveSeqSelectExpr(e, twoState, specContext, false);
} else if (expr is SeqUpdateExpr) {
SeqUpdateExpr e = (SeqUpdateExpr)expr;
bool seqErr = false;
ResolveExpression(e.Seq, twoState, specContext);
assert e.Seq.Type != null; // follows from postcondition of ResolveExpression
Type elementType = new InferredTypeProxy();
if (!UnifyTypes(e.Seq.Type, new SeqType(elementType))) {
Error(expr, "sequence update requires a sequence (got {0})", e.Seq.Type);
seqErr = true;
}
ResolveExpression(e.Index, twoState, specContext);
assert e.Index.Type != null; // follows from postcondition of ResolveExpression
if (!UnifyTypes(e.Index.Type, Type.Int)) {
Error(e.Index, "sequence update requires integer index (got {0})", e.Index.Type);
}
ResolveExpression(e.Value, twoState, specContext);
assert e.Value.Type != null; // follows from postcondition of ResolveExpression
if (!UnifyTypes(e.Value.Type, elementType)) {
Error(e.Value, "sequence update requires the value to have the element type of the sequence (got {0})", e.Value.Type);
}
if (!seqErr) {
expr.Type = e.Seq.Type;
}
} else if (expr is FunctionCallExpr) {
FunctionCallExpr e = (FunctionCallExpr)expr;
ResolveReceiver(e.Receiver, twoState, specContext);
assert e.Receiver.Type != null; // follows from postcondition of ResolveExpression
UserDefinedType ctype;
MemberDecl member = ResolveMember(expr.tok, e.Receiver.Type, e.Name, out ctype);
if (member == null) {
// error has already been reported by ResolveMember
} else if (!(member is Function)) {
Error(expr, "member {0} in class {1} does not refer to a function", e.Name, ((!)ctype).Name);
} else {
Function function = (Function)member;
e.Function = function;
if (!specContext && function.IsGhost) {
Error(expr, "function calls are allowed only in specification contexts (consider declaring the function a 'function method')");
}
if (function.Formals.Count != e.Args.Count) {
Error(expr, "wrong number of function arguments (got {0}, expected {1})", e.Args.Count, function.Formals.Count);
} else {
assert ctype != null; // follows from postcondition of ResolveMember
if (!scope.AllowInstance && !function.IsStatic && e.Receiver is ThisExpr) {
// The call really needs an instance, but that instance is given as 'this', which is not
// available in this context. In most cases, occurrences of 'this' inside e.Receiver would
// have been caught in the recursive call to resolve e.Receiver, but not the specific case
// of e.Receiver being 'this' (explicitly or implicitly), for that case needs to be allowed
// in the event that a class function calls another class function (and note that we need the
// type of the receiver in order to find the method, so we could not have made this check
// earlier).
Error(e.Receiver, "'this' is not allowed in a 'static' context");
}
// build the type substitution map
Dictionary<TypeParameter!,Type!> subst = new Dictionary<TypeParameter!,Type!>();
for (int i = 0; i < ctype.TypeArgs.Count; i++) {
subst.Add(((!)ctype.ResolvedClass).TypeArgs[i], ctype.TypeArgs[i]);
}
foreach (TypeParameter p in function.TypeArgs) {
subst.Add(p, new ParamTypeProxy(p));
}
// type check the arguments
for (int i = 0; i < function.Formals.Count; i++) {
Expression farg = e.Args[i];
ResolveExpression(farg, twoState, specContext);
assert farg.Type != null; // follows from postcondition of ResolveExpression
Type s = SubstType(function.Formals[i].Type, subst);
if (!UnifyTypes(farg.Type, s)) {
Error(expr, "incorrect type of function argument {0} (expected {1}, got {2})", i, s, farg.Type);
}
}
expr.Type = SubstType(function.ResultType, subst);
}
// Resolution termination check
if (currentFunction != null && currentFunction.EnclosingClass != null && function.EnclosingClass != null) {
ModuleDecl callerModule = currentFunction.EnclosingClass.Module;
ModuleDecl calleeModule = function.EnclosingClass.Module;
if (callerModule == calleeModule) {
// intra-module call; this is allowed; add edge in module's call graph
callerModule.CallGraph.AddEdge(currentFunction, function);
if (currentFunction == function) {
currentFunction.IsRecursive = true; // self recursion (mutual recursion is determined elsewhere)
}
} else if (calleeModule.IsDefaultModule) {
// all is fine: everything implicitly imports the default module
} else if (importGraph.Reaches(callerModule, calleeModule)) {
// all is fine: the callee is downstream of the caller
} else {
Error(expr, "inter-module calls must follow the module import relation (so module {0} must transitively import {1})", callerModule.Name, calleeModule.Name);
}
}
}
} else if (expr is OldExpr) {
OldExpr e = (OldExpr)expr;
if (!twoState) {
Error(expr, "old expressions are not allowed in this context");
}
ResolveExpression(e.E, twoState, specContext);
expr.Type = e.E.Type;
} else if (expr is FreshExpr) {
FreshExpr e = (FreshExpr)expr;
if (!twoState) {
Error(expr, "fresh expressions are not allowed in this context");
}
ResolveExpression(e.E, twoState, specContext);
// the type of e.E must be either an object or a collection of objects
Type t = e.E.Type;
assert t != null; // follows from postcondition of ResolveExpression
if (t is CollectionType) {
t = ((CollectionType)t).Arg;
}
if (t is ObjectType) {
// fine
} else if (UserDefinedType.DenotesClass(t) != null) {
// fine
} else {
Error(expr, "the argument of a fresh expression must denote an object or a collection of objects (instead got {0})", e.E.Type);
}
expr.Type = Type.Bool;
} else if (expr is UnaryExpr) {
UnaryExpr e = (UnaryExpr)expr;
ResolveExpression(e.E, twoState, specContext);
assert e.E.Type != null; // follows from postcondition of ResolveExpression
switch (e.Op) {
case UnaryExpr.Opcode.Not:
if (!UnifyTypes(e.E.Type, Type.Bool)) {
Error(expr, "logical negation expects a boolean argument (instead got {0})", e.E.Type);
}
expr.Type = Type.Bool;
break;
case UnaryExpr.Opcode.SeqLength:
if (!UnifyTypes(e.E.Type, new IndexableTypeProxy(new InferredTypeProxy()))) {
Error(expr, "length operator expects a sequence or array argument (instead got {0})", e.E.Type);
}
expr.Type = Type.Int;
break;
default:
assert false; // unexpected unary operator
}
} else if (expr is BinaryExpr) {
BinaryExpr e = (BinaryExpr)expr;
ResolveExpression(e.E0, twoState, specContext);
assert e.E0.Type != null; // follows from postcondition of ResolveExpression
ResolveExpression(e.E1, twoState, specContext);
assert e.E1.Type != null; // follows from postcondition of ResolveExpression
switch (e.Op) {
case BinaryExpr.Opcode.Iff:
case BinaryExpr.Opcode.Imp:
case BinaryExpr.Opcode.And:
case BinaryExpr.Opcode.Or:
if (!UnifyTypes(e.E0.Type, Type.Bool)) {
Error(expr, "first argument to {0} must be of type bool (instead got {1})", BinaryExpr.OpcodeString(e.Op), e.E0.Type);
}
if (!UnifyTypes(e.E1.Type, Type.Bool)) {
Error(expr, "second argument to {0} must be of type bool (instead got {1})", BinaryExpr.OpcodeString(e.Op), e.E1.Type);
}
expr.Type = Type.Bool;
break;
case BinaryExpr.Opcode.Eq:
case BinaryExpr.Opcode.Neq:
if (!UnifyTypes(e.E0.Type, e.E1.Type)) {
Error(expr, "arguments must have the same type (got {0} and {1})", e.E0.Type, e.E1.Type);
}
expr.Type = Type.Bool;
break;
case BinaryExpr.Opcode.Disjoint:
if (!UnifyTypes(e.E0.Type, new SetType(new InferredTypeProxy()))) {
Error(expr, "arguments must be of a set type (got {0})", e.E0.Type);
}
if (!UnifyTypes(e.E0.Type, e.E1.Type)) {
Error(expr, "arguments must have the same type (got {0} and {1})", e.E0.Type, e.E1.Type);
}
expr.Type = Type.Bool;
break;
case BinaryExpr.Opcode.Lt:
case BinaryExpr.Opcode.Le:
case BinaryExpr.Opcode.Add:
{
if (e.Op == BinaryExpr.Opcode.Lt && e.E0.Type.IsDatatype) {
if (!UnifyTypes(e.E1.Type, new DatatypeProxy())) {
Error(expr, "arguments to rank comparison must be datatypes (instead of {0})", e.E1.Type);
}
if (!specContext) {
Error(expr, "rank comparisons are allowed only in specification and ghost contexts");
}
expr.Type = Type.Bool;
} else {
bool err = false;
if (!UnifyTypes(e.E0.Type, new OperationTypeProxy(true))) {
Error(expr, "arguments to {0} must be int or a collection type (instead got {1})", BinaryExpr.OpcodeString(e.Op), e.E0.Type);
err = true;
}
if (!UnifyTypes(e.E1.Type, e.E0.Type)) {
Error(expr, "arguments to {0} must have the same type (got {1} and {2})", BinaryExpr.OpcodeString(e.Op), e.E0.Type, e.E1.Type);
err = true;
}
if (e.Op != BinaryExpr.Opcode.Add) {
expr.Type = Type.Bool;
} else if (!err) {
expr.Type = e.E0.Type;
}
}
}
break;
case BinaryExpr.Opcode.Sub:
case BinaryExpr.Opcode.Mul:
case BinaryExpr.Opcode.Gt:
case BinaryExpr.Opcode.Ge:
{
if (e.Op == BinaryExpr.Opcode.Gt && e.E0.Type.IsDatatype) {
if (!UnifyTypes(e.E1.Type, new DatatypeProxy())) {
Error(expr, "arguments to rank comparison must be datatypes (instead of {0})", e.E1.Type);
}
if (!specContext) {
Error(expr, "rank comparisons are allowed only in specification and ghost contexts");
}
expr.Type = Type.Bool;
} else {
bool err = false;
if (!UnifyTypes(e.E0.Type, new OperationTypeProxy(false))) {
Error(expr, "arguments to {0} must be int or a set (instead got {1})", BinaryExpr.OpcodeString(e.Op), e.E0.Type);
err = true;
}
if (!UnifyTypes(e.E1.Type, e.E0.Type)) {
Error(expr, "arguments to {0} must have the same type (got {1} and {2})", BinaryExpr.OpcodeString(e.Op), e.E0.Type, e.E1.Type);
err = true;
}
if (e.Op == BinaryExpr.Opcode.Gt || e.Op == BinaryExpr.Opcode.Ge) {
expr.Type = Type.Bool;
} else if (!err) {
expr.Type = e.E0.Type;
}
}
}
break;
case BinaryExpr.Opcode.In:
case BinaryExpr.Opcode.NotIn:
if (!UnifyTypes(e.E1.Type, new CollectionTypeProxy(e.E0.Type))) {
Error(expr, "second argument to {0} must be a set or sequence of type {1} (instead got {2})", BinaryExpr.OpcodeString(e.Op), e.E0.Type, e.E1.Type);
}
expr.Type = Type.Bool;
break;
case BinaryExpr.Opcode.Div:
case BinaryExpr.Opcode.Mod:
if (!UnifyTypes(e.E0.Type, Type.Int)) {
Error(expr, "first argument to {0} must be of type int (instead got {1})", BinaryExpr.OpcodeString(e.Op), e.E0.Type);
}
if (!UnifyTypes(e.E1.Type, Type.Int)) {
Error(expr, "second argument to {0} must be of type int (instead got {1})", BinaryExpr.OpcodeString(e.Op), e.E1.Type);
}
expr.Type = Type.Int;
break;
default:
assert false; // unexpected operator
}
e.ResolvedOp = ResolveOp(e.Op, e.E1.Type);
} else if (expr is QuantifierExpr) {
QuantifierExpr e = (QuantifierExpr)expr;
scope.PushMarker();
if (!specContext) {
Error(expr, "quantifiers are allowed only in specification contexts");
}
foreach (BoundVar v in e.BoundVars) {
if (!scope.Push(v.Name, v)) {
Error(v, "Duplicate bound-variable name: {0}", v.Name);
}
ResolveType(v.Type);
}
ResolveExpression(e.Body, twoState, specContext);
assert e.Body.Type != null; // follows from postcondition of ResolveExpression
if (!UnifyTypes(e.Body.Type, Type.Bool)) {
Error(expr, "body of quantifier must be of type bool (instead got {0})", e.Body.Type);
}
// Since the body is more likely to infer the types of the bound variables, resolve it
// first (above) and only then resolve the attributes and triggers (below).
ResolveAttributes(e.Attributes, twoState);
ResolveTriggers(e.Trigs, twoState);
scope.PopMarker();
expr.Type = Type.Bool;
} else if (expr is WildcardExpr) {
expr.Type = new SetType(new ObjectType());
} else if (expr is ITEExpr) {
ITEExpr e = (ITEExpr)expr;
ResolveExpression(e.Test, twoState, specContext);
assert e.Test.Type != null; // follows from postcondition of ResolveExpression
ResolveExpression(e.Thn, twoState, specContext);
assert e.Thn.Type != null; // follows from postcondition of ResolveExpression
ResolveExpression(e.Els, twoState, specContext);
assert e.Els.Type != null; // follows from postcondition of ResolveExpression
if (!UnifyTypes(e.Test.Type, Type.Bool)) {
Error(expr, "guard condition in if-then-else expression must be a boolean (instead got {0})", e.Test.Type);
}
if (UnifyTypes(e.Thn.Type, e.Els.Type)) {
expr.Type = e.Thn.Type;
} else {
Error(expr, "the two branches of an if-then-else expression must have the same type (got {0} and {1})", e.Thn.Type, e.Els.Type);
}
} else if (expr is MatchExpr) {
MatchExpr me = (MatchExpr)expr;
assert !twoState; // currently, match expressions are allowed only at the outermost level of function bodies
ResolveExpression(me.Source, twoState, specContext);
assert me.Source.Type != null; // follows from postcondition of ResolveExpression
UserDefinedType sourceType = null;
DatatypeDecl dtd = null;
Dictionary<TypeParameter!,Type!> subst = new Dictionary<TypeParameter!,Type!>();
if (me.Source.Type.IsDatatype) {
sourceType = (UserDefinedType)me.Source.Type;
dtd = (DatatypeDecl!)sourceType.ResolvedClass;
}
Dictionary<string!,DatatypeCtor!> ctors;
if (dtd == null) {
Error(me.Source, "the type of the match source expression must be a datatype");
ctors = null;
} else {
assert sourceType != null; // dtd and sourceType are set together above
ctors = datatypeCtors[dtd];
assert ctors != null; // dtd should have been inserted into datatypeCtors during a previous resolution stage
IdentifierExpr ie = me.Source as IdentifierExpr;
if (ie == null || !(ie.Var is Formal)) {
Error(me.Source.tok, "match source expression must be a formal parameter of the enclosing function");
}
// build the type-parameter substitution map for this use of the datatype
for (int i = 0; i < dtd.TypeArgs.Count; i++) {
subst.Add(dtd.TypeArgs[i], sourceType.TypeArgs[i]);
}
}
Dictionary<string!,object> memberNamesUsed = new Dictionary<string!,object>(); // this is really a set
expr.Type = new InferredTypeProxy();
foreach (MatchCaseExpr mc in me.Cases) {
DatatypeCtor ctor = null;
if (ctors != null) {
assert dtd != null;
if (!ctors.TryGetValue(mc.Id, out ctor)) {
Error(mc.tok, "member {0} does not exist in datatype {1}", mc.Id, dtd.Name);
} else {
assert ctor != null; // follows from postcondition of TryGetValue
mc.Ctor = ctor;
if (ctor.Formals.Count != mc.Arguments.Count) {
Error(mc.tok, "member {0} has wrong number of formals (found {1}, expected {2})", mc.Arguments.Count, ctor.Formals.Count);
}
if (memberNamesUsed.ContainsKey(mc.Id)) {
Error(mc.tok, "member {0} appears in more than one case", mc.Id);
} else {
memberNamesUsed.Add(mc.Id, null); // add mc.Id to the set of names used
}
}
}
scope.PushMarker();
if (ctor != null) {
// add the constructor's own type parameters to the substitution map
foreach (TypeParameter p in ctor.TypeArgs) {
subst.Add(p, new ParamTypeProxy(p));
}
}
int i = 0;
foreach (BoundVar v in mc.Arguments) {
if (!scope.Push(v.Name, v)) {
Error(v, "Duplicate parameter name: {0}", v.Name);
}
ResolveType(v.Type);
if (ctor != null && i < ctor.Formals.Count) {
Formal formal = ctor.Formals[i];
Type st = SubstType(formal.Type, subst);
if (!UnifyTypes(v.Type, st)) {
Error(expr, "the declared type of the formal ({0}) does not agree with the corresponding type in the constructor's signature ({1})", v.Type, st);
}
v.IsGhost = formal.IsGhost;
}
i++;
}
ResolveExpression(mc.Body, twoState, specContext);
assert mc.Body.Type != null; // follows from postcondition of ResolveExpression
if (!UnifyTypes(expr.Type, mc.Body.Type)) {
Error(mc.Body.tok, "type of case bodies do not agree (found {0}, previous types {1})", mc.Body.Type, expr.Type);
}
scope.PopMarker();
}
if (dtd != null && memberNamesUsed.Count != dtd.Ctors.Count) {
Error(expr, "match expression does not cover all constructors");
}
} else {
assert false; // unexpected expression
}
if (expr.Type == null) {
// some resolution error occurred
expr.Type = Type.Flexible;
}
}
void ResolveReceiver(Expression! expr, bool twoState, bool specContext)
requires currentClass != null;
ensures expr.Type != null;
{
if (expr is ThisExpr) {
// Allow 'this' here, regardless of scope.AllowInstance. The caller is responsible for
// making sure 'this' does not really get used when it's not available.
expr.Type = GetThisType(expr.tok, currentClass);
} else {
ResolveExpression(expr, twoState, specContext);
}
}
void ResolveSeqSelectExpr(SeqSelectExpr! e, bool twoState, bool specContext, bool allowNonUnitArraySelection) {
bool seqErr = false;
ResolveExpression(e.Seq, twoState, specContext);
assert e.Seq.Type != null; // follows from postcondition of ResolveExpression
Type elementType = new InferredTypeProxy();
Type expectedType;
if (e.SelectOne || allowNonUnitArraySelection) {
expectedType = new IndexableTypeProxy(elementType);
} else {
expectedType = new SeqType(elementType);
}
if (!UnifyTypes(e.Seq.Type, expectedType)) {
Error(e, "sequence/array selection requires a sequence or array (got {0})", e.Seq.Type);
seqErr = true;
}
if (e.E0 != null) {
ResolveExpression(e.E0, twoState, specContext);
assert e.E0.Type != null; // follows from postcondition of ResolveExpression
if (!UnifyTypes(e.E0.Type, Type.Int)) {
Error(e.E0, "sequence/array selection requires integer indices (got {0})", e.E0.Type);
}
}
if (e.E1 != null) {
ResolveExpression(e.E1, twoState, specContext);
assert e.E1.Type != null; // follows from postcondition of ResolveExpression
if (!UnifyTypes(e.E1.Type, Type.Int)) {
Error(e.E1, "sequence/array selection requires integer indices (got {0})", e.E1.Type);
}
}
if (!seqErr) {
if (e.SelectOne) {
e.Type = elementType;
} else {
e.Type = e.Seq.Type;
}
}
}
/// <summary>
/// Note: this method is allowed to be called even if "type" does not make sense for "op", as might be the case if
/// resolution of the binary expression failed. If so, an arbitrary resolved opcode is returned.
/// </summary>
BinaryExpr.ResolvedOpcode ResolveOp(BinaryExpr.Opcode op, Type! operandType) {
switch (op) {
case BinaryExpr.Opcode.Iff: return BinaryExpr.ResolvedOpcode.Iff;
case BinaryExpr.Opcode.Imp: return BinaryExpr.ResolvedOpcode.Imp;
case BinaryExpr.Opcode.And: return BinaryExpr.ResolvedOpcode.And;
case BinaryExpr.Opcode.Or: return BinaryExpr.ResolvedOpcode.Or;
case BinaryExpr.Opcode.Eq:
if (operandType is SetType) {
return BinaryExpr.ResolvedOpcode.SetEq;
} else if (operandType is SeqType) {
return BinaryExpr.ResolvedOpcode.SeqEq;
} else {
return BinaryExpr.ResolvedOpcode.EqCommon;
}
case BinaryExpr.Opcode.Neq:
if (operandType is SetType) {
return BinaryExpr.ResolvedOpcode.SetNeq;
} else if (operandType is SeqType) {
return BinaryExpr.ResolvedOpcode.SeqNeq;
} else {
return BinaryExpr.ResolvedOpcode.NeqCommon;
}
case BinaryExpr.Opcode.Disjoint: return BinaryExpr.ResolvedOpcode.Disjoint;
case BinaryExpr.Opcode.Lt:
if (operandType.IsDatatype) {
return BinaryExpr.ResolvedOpcode.RankLt;
} else if (operandType is SetType) {
return BinaryExpr.ResolvedOpcode.ProperSubset;
} else if (operandType is SeqType) {
return BinaryExpr.ResolvedOpcode.ProperPrefix;
} else {
return BinaryExpr.ResolvedOpcode.Lt;
}
case BinaryExpr.Opcode.Le:
if (operandType is SetType) {
return BinaryExpr.ResolvedOpcode.Subset;
} else if (operandType is SeqType) {
return BinaryExpr.ResolvedOpcode.Prefix;
} else {
return BinaryExpr.ResolvedOpcode.Le;
}
case BinaryExpr.Opcode.Add:
if (operandType is SetType) {
return BinaryExpr.ResolvedOpcode.Union;
} else if (operandType is SeqType) {
return BinaryExpr.ResolvedOpcode.Concat;
} else {
return BinaryExpr.ResolvedOpcode.Add;
}
case BinaryExpr.Opcode.Sub:
if (operandType is SetType) {
return BinaryExpr.ResolvedOpcode.SetDifference;
} else {
return BinaryExpr.ResolvedOpcode.Sub;
}
case BinaryExpr.Opcode.Mul:
if (operandType is SetType) {
return BinaryExpr.ResolvedOpcode.Intersection;
} else {
return BinaryExpr.ResolvedOpcode.Mul;
}
case BinaryExpr.Opcode.Gt:
if (operandType.IsDatatype) {
return BinaryExpr.ResolvedOpcode.RankGt;
} else if (operandType is SetType) {
return BinaryExpr.ResolvedOpcode.ProperSuperset;
} else {
return BinaryExpr.ResolvedOpcode.Gt;
}
case BinaryExpr.Opcode.Ge:
if (operandType is SetType) {
return BinaryExpr.ResolvedOpcode.Superset;
} else {
return BinaryExpr.ResolvedOpcode.Ge;
}
case BinaryExpr.Opcode.In:
if (operandType is SetType) {
return BinaryExpr.ResolvedOpcode.InSet;
} else {
return BinaryExpr.ResolvedOpcode.InSeq;
}
case BinaryExpr.Opcode.NotIn:
if (operandType is SetType) {
return BinaryExpr.ResolvedOpcode.NotInSet;
} else {
return BinaryExpr.ResolvedOpcode.NotInSeq;
}
case BinaryExpr.Opcode.Div: return BinaryExpr.ResolvedOpcode.Div;
case BinaryExpr.Opcode.Mod: return BinaryExpr.ResolvedOpcode.Mod;
default:
assert false; // unexpected operator
}
}
/// <summary>
/// Returns whether or not 'expr' has any subexpression that uses some feature (like a ghost or quantifier)
/// that is allowed only in specification contexts.
/// Requires 'expr' to be a successfully resolved expression.
/// </summary>
bool UsesSpecFeatures(Expression! expr)
requires currentClass != null;
{
if (expr is LiteralExpr) {
return false;
} else if (expr is ThisExpr) {
return false;
} else if (expr is IdentifierExpr) {
IdentifierExpr e = (IdentifierExpr)expr;
return ((!)e.Var).IsGhost;
} else if (expr is DatatypeValue) {
DatatypeValue dtv = (DatatypeValue)expr;
return exists{Expression arg in dtv.Arguments; UsesSpecFeatures(arg)};
} else if (expr is DisplayExpression) {
DisplayExpression e = (DisplayExpression)expr;
return exists{Expression ee in e.Elements; UsesSpecFeatures(ee)};
} else if (expr is FieldSelectExpr) {
FieldSelectExpr e = (FieldSelectExpr)expr;
return ((!)e.Field).IsGhost || UsesSpecFeatures(e.Obj);
} else if (expr is SeqSelectExpr) {
SeqSelectExpr e = (SeqSelectExpr)expr;
return UsesSpecFeatures(e.Seq) ||
(e.E0 != null && UsesSpecFeatures(e.E0)) ||
(e.E1 != null && UsesSpecFeatures(e.E1));
} else if (expr is SeqUpdateExpr) {
SeqUpdateExpr e = (SeqUpdateExpr)expr;
return UsesSpecFeatures(e.Seq) ||
(e.Index != null && UsesSpecFeatures(e.Index)) ||
(e.Value != null && UsesSpecFeatures(e.Value));
} else if (expr is FunctionCallExpr) {
FunctionCallExpr e = (FunctionCallExpr)expr;
if (((!)e.Function).IsGhost) {
return true;
}
return exists{Expression arg in e.Args; UsesSpecFeatures(arg)};
} else if (expr is OldExpr) {
OldExpr e = (OldExpr)expr;
return UsesSpecFeatures(e.E);
} else if (expr is FreshExpr) {
FreshExpr e = (FreshExpr)expr;
return UsesSpecFeatures(e.E);
} else if (expr is UnaryExpr) {
UnaryExpr e = (UnaryExpr)expr;
return UsesSpecFeatures(e.E);
} else if (expr is BinaryExpr) {
BinaryExpr e = (BinaryExpr)expr;
if (e.ResolvedOp == BinaryExpr.ResolvedOpcode.RankLt || e.ResolvedOp == BinaryExpr.ResolvedOpcode.RankGt) {
return true;
}
return UsesSpecFeatures(e.E0) || UsesSpecFeatures(e.E1);
} else if (expr is QuantifierExpr) {
return true;
} else if (expr is WildcardExpr) {
return false;
} else if (expr is ITEExpr) {
ITEExpr e = (ITEExpr)expr;
return UsesSpecFeatures(e.Test) || UsesSpecFeatures(e.Thn) || UsesSpecFeatures(e.Els);
} else if (expr is MatchExpr) {
MatchExpr me = (MatchExpr)expr;
if (UsesSpecFeatures(me.Source)) {
return true;
}
return exists{MatchCaseExpr mc in me.Cases; UsesSpecFeatures(mc.Body)};
} else {
assert false; // unexpected expression
}
}
}
class Scope<Thing> where Thing : class {
[Rep] readonly List<string>! names = new List<string>(); // a null means a marker
[Rep] readonly List<Thing?>! things = new List<Thing?>();
int scopeSizeWhereInstancesWereDisallowed = -1;
#region SpecSharp compiler annoyance
invariant names.Count == things.Count;
invariant -1 <= scopeSizeWhereInstancesWereDisallowed && scopeSizeWhereInstancesWereDisallowed <= names.Count;
#endregion
public bool AllowInstance {
get { return scopeSizeWhereInstancesWereDisallowed == -1; }
set
requires AllowInstance && !value; // only allowed to change from true to false (that's all that's currently needed in Dafny); Pop is what can make the change in the other direction
{
scopeSizeWhereInstancesWereDisallowed = names.Count;
}
}
public void PushMarker() {
names.Add(null);
things.Add(null);
}
public void PopMarker() {
int n = names.Count;
while (true) {
n--;
if (names[n] == null) {
break;
}
}
names.RemoveRange(n, names.Count - n);
things.RemoveRange(n, things.Count - n);
if (names.Count < scopeSizeWhereInstancesWereDisallowed) {
scopeSizeWhereInstancesWereDisallowed = -1;
}
}
// Pushes name-->var association and returns "true", if name has not already been pushed since the last marker.
// If name already has been pushed since the last marker, does nothing and returns "false".
public bool Push(string! name, Thing! thing) {
if (Find(name, true) != null) {
return false;
} else {
names.Add(name);
things.Add(thing);
return true;
}
}
Thing? Find(string! name, bool topScopeOnly) {
for (int n = names.Count; 0 <= --n; ) {
if (names[n] == null) {
if (topScopeOnly) {
return null; // no present
}
} else if (names[n] == name) {
Thing t = things[n];
assert t != null;
return t;
}
}
return null; // not present
}
public Thing? Find(string! name) {
return Find(name, false);
}
}
}
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