Catch duplicate top-level module names; fix dropping of constraints during incremental elaboration; document treatment of record types as type class instance types

3 files changed, 15 insertions, 3 deletions

diff --git a/doc/manual.tex b/doc/manual.tex
index 41e07a52..06731357 100644
--- a/doc/manual.tex
+++ b/doc/manual.tex
@@ -579,7 +579,7 @@ A signature item or declaration $\mt{type} \; x$ or $\mt{type} \; x = \tau$ is e
 
 A signature item or declaration $\mt{class} \; x = \lambda y \Rightarrow c$ may be abbreviated $\mt{class} \; x \; y = c$.
 
-Handling of implicit and explicit constructor arguments may be tweaked with some prefixes to variable references.  An expression $@x$ is a version of $x$ where all type class instance and disjointness arguments have been made explicit.  (For the purposes of this paragraph, the type family $\mt{Top.folder}$ is a type class, though it isn't marked as one by the usual means.)  An expression $@@x$ achieves the same effect, additionally making explicit all implicit constructor arguments.  The default is that implicit arguments are inserted automatically after any reference to a variable, or after any application of a variable to one or more arguments.  For such an expression, implicit wildcard arguments are added for the longest prefix of the expression's type consisting only of implicit polymorphism, type class instances, and disjointness obligations.  The same syntax works for variables projected out of modules and for capitalized variables (datatype constructors).
+Handling of implicit and explicit constructor arguments may be tweaked with some prefixes to variable references.  An expression $@x$ is a version of $x$ where all type class instance and disjointness arguments have been made explicit.  (For the purposes of this paragraph, the type family $\mt{Top.folder}$ is a type class, though it isn't marked as one by the usual means; and any record type is considered to be a type class instance type when every field's type is a type class instance type.)  An expression $@@x$ achieves the same effect, additionally making explicit all implicit constructor arguments.  The default is that implicit arguments are inserted automatically after any reference to a variable, or after any application of a variable to one or more arguments.  For such an expression, implicit wildcard arguments are added for the longest prefix of the expression's type consisting only of implicit polymorphism, type class instances, and disjointness obligations.  The same syntax works for variables projected out of modules and for capitalized variables (datatype constructors).
 
 At the expression level, an analogue is available of the composite $\lambda$ form for constructors.  We define the language of binders as $b ::= p \mid [x] \mid [x \; ? \; \kappa] \mid X \mid [c \sim c]$.  A lone variable $[x]$ stands for an implicit constructor variable of unspecified kind.  The standard value-level function binder is recovered as the type-annotated pattern form $x : \tau$.  It is a compile-time error to include a pattern $p$ that does not match every value of the appropriate type.
 
diff --git a/src/compiler.sml b/src/compiler.sml
index 575d95c7..45d87b6a 100644
--- a/src/compiler.sml
+++ b/src/compiler.sml
@@ -943,8 +943,11 @@ val parse = {
                                      first = ErrorMsg.dummyPos,
                                      last = ErrorMsg.dummyPos}
 
+                          val urt = OS.FileSys.modTime ur
+                          val urst = (OS.FileSys.modTime urs) handle _ => urt
+
                           val ds = #func parseUr ur
-                          val d = (Source.DStr (mname, sgnO, if !Elaborate.incremental then SOME (OS.FileSys.modTime ur) else NONE,
+                          val d = (Source.DStr (mname, sgnO, if !Elaborate.incremental then SOME (if Time.> (urt, urst) then urt else urst) else NONE,
                                                 (Source.StrConst ds, loc)), loc)
 
                           val fname = OS.Path.mkCanonical fname
@@ -1078,6 +1081,15 @@ val parse = {
                                    NONE => ds
                                  | SOME v => ds @ [(Source.DOnError v, loc)]
                   in
+                      ignore (List.foldl (fn (d, used) =>
+                                             case #1 d of
+                                                 Source.DStr (x, _, _, _) =>
+                                                 if SS.member (used, x) then
+                                                     (ErrorMsg.errorAt (#2 d) ("Duplicate top-level module name " ^ x);
+                                                      used)
+                                                 else
+                                                     SS.add (used, x)
+                                               | _ => used) SS.empty ds);
                       ds
                   end handle Empty => ds
               end,
diff --git a/src/elaborate.sml b/src/elaborate.sml
index 41e9e9ab..f098b580 100644
--- a/src/elaborate.sml
+++ b/src/elaborate.sml
@@ -3934,7 +3934,7 @@ and elabDecl (dAll as (d, loc), (env, denv, gs)) =
                          val env' = E.declBinds env d
                          val denv' = dopenConstraints (loc, env', denv) {str = x, strs = []}
                      in
-                         ([d], (env', denv', []))
+                         ([d], (env', denv', gs))
                      end
                    | NONE =>
                      let