//----------------------------------------------------------------------------- // // 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! classes = new Dictionary(); readonly Dictionary!>! classMembers = new Dictionary!>(); readonly Dictionary!>! datatypeCtors = new Dictionary!>(); readonly Graph! importGraph = new Graph(); bool checkRefinements = true; // used to indicate a cycle in refinements public void ResolveProgram(Program! prog) { // register modules Dictionary modules = new Dictionary(); 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 Graph! refines = new Graph(); 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); foreach (TopLevelDecl! decl in m.TopLevelDecls) refines.AddVertex(decl); } // check for cycles in the import graph List 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 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) { ClassRefinementDecl! rdecl = (ClassRefinementDecl) decl; ResolveTopLevelRefinement(rdecl); if (rdecl.Refined != null) refines.AddEdge(rdecl, rdecl.Refined); } // attempt finding refinement cycles List refinesCycle = refines.TryFindCycle(); if (refinesCycle != null) { string cy = ""; string sep = ""; foreach (TopLevelDecl decl in refinesCycle) { cy = decl + sep + cy; sep = " -> "; } Error(refinesCycle[0], "Detected a cyclic refinement declaration: {0}", cy); checkRefinements = false; } // resolve top-level declarations Graph datatypeDependencies = new Graph(); 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! 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 members = new Dictionary(); 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 ctors = new Dictionary(); 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) { 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 } } public void ResolveTopLevelDecls_Signatures(List! declarations, Graph! 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! declarations, Graph! 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! allTypeParameters = new Scope(); readonly Scope! scope = new Scope(); readonly Scope! labeledStatements = new Scope(); /// /// Assumes type parameters have already been pushed /// 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; if (refined != null) { assert classMembers.ContainsKey(refined); Dictionary members = classMembers[refined]; // resolve abstracted fields in the refined class List fields = new List(); 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; if (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; } /// /// Assumes type parameters have already been pushed, and that all types in class members have been resolved /// 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; if (currentClass is ClassRefinementDecl) { // should have already been resolved if (((ClassRefinementDecl)currentClass).Refined != null) { 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 { Error(member, "Refinement methods can only be declared in refinement classes: {0}", member.Name); } } } else if (member is CouplingInvariant) { CouplingInvariant inv = (CouplingInvariant)member; if (inv.Refined != null) { inv.Formals = new List(); 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; } /// /// Assumes type parameters have already been pushed /// void ResolveCtorTypes(DatatypeDecl! dt, Graph! 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); } } } } /// /// 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. /// void SccStratosphereCheck(DatatypeDecl! startingPoint, Graph! dependencies) { List scc = dependencies.GetSCC(startingPoint); List! cleared = new List(); // 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; } } } /// /// 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. /// bool StratosphereCheck(DatatypeDecl! dt, Graph! dependencies, List! 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! 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! tparams, bool emitErrors, TypeParameter.ParentType! parent) { // push type arguments of the refined class if (checkRefinements && parent is ClassRefinementDecl) { ClassDecl refined = ((ClassRefinementDecl)parent).Refined; if (refined != null) ResolveTypeParameters(refined.TypeArgs, false, refined); } // 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); } } } /// /// Assumes type parameters have already been pushed /// 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(); } /// /// Assumes type parameters have already been pushed /// 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); } } /// /// Assumes type parameters have already been pushed /// 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(); } /// /// Assumes type parameters have already been pushed /// 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 a new scope that will also include the outermost-level locals of the body // Don't care about any duplication errors among the out-parameters, since they have already been reported scope.PushMarker(); 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) { ResolveBlockStatement(m.Body, m.IsGhost, m); } scope.PopMarker(); // for the out-parameters and outermost-level locals scope.PopMarker(); // for the in-parameters } /// /// Assumes type parameters have already been pushed /// 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,seq and b says int,set; the intersection is set 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 lhsNameSet = new Dictionary(); 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 subst = new Dictionary(); 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(); ResolveBlockStatement((BlockStmt)stmt, specContextOnly, method); 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 subst = new Dictionary(); if (s.Source.Type.IsDatatype) { sourceType = (UserDefinedType)s.Source.Type; dtd = (DatatypeDecl!)sourceType.ResolvedClass; } Dictionary 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 memberNamesUsed = new Dictionary(); // 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; } } void ResolveBlockStatement(BlockStmt! blockStmt, bool specContextOnly, Method! method) { int labelsToPop = 0; foreach (Statement ss in blockStmt.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(); } } 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! 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 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(); 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 args = new List(); foreach (TypeParameter tp in cl.TypeArgs) { args.Add(new UserDefinedType(tok, tp.Name, tp)); } return new UserDefinedType(tok, cl.Name, cl, args); } /// /// "twoState" implies that "old" and "fresh" expressions are allowed /// 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 gt = new List(dt.TypeArgs.Count); Dictionary subst = new Dictionary(); 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 subst = new Dictionary(); 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 subst = new Dictionary(); 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 subst = new Dictionary(); if (me.Source.Type.IsDatatype) { sourceType = (UserDefinedType)me.Source.Type; dtd = (DatatypeDecl!)sourceType.ResolvedClass; } Dictionary 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 memberNamesUsed = new Dictionary(); // 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; } } } /// /// 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. /// 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 } } /// /// 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. /// 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 where Thing : class { [Rep] readonly List! names = new List(); // a null means a marker [Rep] readonly List! things = new List(); 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); } } }