Improve error messages of unexpected arguments

When we get GenericBindings such as ::<A=...> this is not allowed
int this context. We can also improve the unexpected number of argument
errors to print the number of expected vs received arguments.

1 files changed, 20 insertions, 4 deletions

diff --git a/gcc/rust/typecheck/rust-tyty.cc b/gcc/rust/typecheck/rust-tyty.cc
index b75c139..c8f5f19 100644
--- a/gcc/rust/typecheck/rust-tyty.cc
+++ b/gcc/rust/typecheck/rust-tyty.cc
@@ -211,16 +211,32 @@ SubstitutionParamMapping::override_context ()
 SubstitutionArgumentMappings
 SubstitutionRef::get_mappings_from_generic_args (HIR::GenericArgs &args)
 {
-  if (args.get_type_args ().size () != substitutions.size ())
+  if (args.get_binding_args ().size () > 0)
     {
       rust_error_at (args.get_locus (),
-		     "Invalid number of generic arguments to generic type");
+		     "associated type bindings are not allowed here");
       return SubstitutionArgumentMappings::error ();
     }
 
-  std::vector<SubstitutionArg> mappings;
+  if (args.get_type_args ().size () > substitutions.size ())
+    {
+      rust_error_at (
+	args.get_locus (),
+	"generic item takes at most %lu type arguments but %lu were supplied",
+	substitutions.size (), args.get_type_args ().size ());
+      return SubstitutionArgumentMappings::error ();
+    }
 
-  // FIXME does not support binding yet
+  if (args.get_type_args ().size () < substitutions.size ())
+    {
+      rust_error_at (
+	args.get_locus (),
+	"generic item takes at least %lu type arguments but %lu were supplied",
+	substitutions.size (), args.get_type_args ().size ());
+      return SubstitutionArgumentMappings::error ();
+    }
+
+  std::vector<SubstitutionArg> mappings;
   for (auto &arg : args.get_type_args ())
     {
       BaseType *resolved = Resolver::TypeCheckType::Resolve (arg.get ());