gccrs: Fix ICE when hitting invalid types for generics

We need to check upfront if the type is valid or not. Then
error with a decent message.

Fixes Rust-GCC#3643
Fixes Rust-GCC#3646
Fixes Rust-GCC#3654
Fixes Rust-GCC#3663
Fixes Rust-GCC#3671

gcc/rust/ChangeLog:

	* resolve/rust-ast-resolve-type.cc (ResolveRelativeTypePath::go): fix error msg
	* typecheck/rust-substitution-mapper.cc (SubstMapper::Resolve): add validation
	(SubstMapper::valid_type): new check
	(SubstMapper::visit): check if can resolve
	* typecheck/rust-substitution-mapper.h: new prototype

gcc/testsuite/ChangeLog:

	* rust/compile/nr2/exclude: nr2 is missing type path error
	* rust/compile/issue-3643.rs: New test.
	* rust/compile/issue-3646.rs: New test.
	* rust/compile/issue-3654.rs: New test.
	* rust/compile/issue-3663.rs: New test.
	* rust/compile/issue-3671.rs: New test.

Signed-off-by: Philip Herron <herron.philip@googlemail.com>

3 files changed, 29 insertions, 2 deletions

diff --git a/gcc/rust/resolve/rust-ast-resolve-type.cc b/gcc/rust/resolve/rust-ast-resolve-type.cc
index c1c4022..135504e 100644
--- a/gcc/rust/resolve/rust-ast-resolve-type.cc
+++ b/gcc/rust/resolve/rust-ast-resolve-type.cc
@@ -357,7 +357,7 @@ ResolveRelativeTypePath::go (AST::TypePath &path, NodeId &resolved_node_id)
 	{
 	  rust_error_at (segment->get_locus (), ErrorCode::E0412,
 			 "could not resolve type path %qs",
-			 segment->as_string ().c_str ());
+			 segment->get_ident_segment ().as_string ().c_str ());
 	  return false;
 	}
     }
diff --git a/gcc/rust/typecheck/rust-substitution-mapper.cc b/gcc/rust/typecheck/rust-substitution-mapper.cc
index 20fe8f0..878c4d5 100644
--- a/gcc/rust/typecheck/rust-substitution-mapper.cc
+++ b/gcc/rust/typecheck/rust-substitution-mapper.cc
@@ -34,6 +34,15 @@ SubstMapper::Resolve (TyTy::BaseType *base, location_t locus,
 		      HIR::GenericArgs *generics,
 		      const std::vector<TyTy::Region> &regions)
 {
+  if (!valid_type (base))
+    {
+      rich_location r (line_table, locus);
+      r.add_fixit_remove (generics->get_locus ());
+      rust_error_at (r, ErrorCode::E0109,
+		     "generic arguments are not allowed for this type");
+      return base;
+    }
+
   SubstMapper mapper (base->get_ref (), generics, regions, locus);
   base->accept_vis (mapper);
   rust_assert (mapper.resolved != nullptr);
@@ -47,6 +56,17 @@ SubstMapper::InferSubst (TyTy::BaseType *base, location_t locus)
 }
 
 bool
+SubstMapper::valid_type (TyTy::BaseType *base)
+{
+  bool is_fn = base->is<TyTy::FnType> ();
+  bool is_adt = base->is<TyTy::ADTType> ();
+  bool is_placeholder = base->is<TyTy::PlaceholderType> ();
+  bool is_projection = base->is<TyTy::ProjectionType> ();
+
+  return is_fn || is_adt || is_placeholder || is_projection;
+}
+
+bool
 SubstMapper::have_generic_args () const
 {
   return generics != nullptr;
@@ -103,7 +123,12 @@ SubstMapper::visit (TyTy::ADTType &type)
 void
 SubstMapper::visit (TyTy::PlaceholderType &type)
 {
-  rust_assert (type.can_resolve ());
+  if (!type.can_resolve ())
+    {
+      resolved = &type;
+      return;
+    }
+
   resolved = SubstMapper::Resolve (type.resolve (), locus, generics, regions);
 }
 
diff --git a/gcc/rust/typecheck/rust-substitution-mapper.h b/gcc/rust/typecheck/rust-substitution-mapper.h
index a0aba56..2f03e4b 100644
--- a/gcc/rust/typecheck/rust-substitution-mapper.h
+++ b/gcc/rust/typecheck/rust-substitution-mapper.h
@@ -37,6 +37,8 @@ public:
 
   bool have_generic_args () const;
 
+  static bool valid_type (TyTy::BaseType *base);
+
   void visit (TyTy::FnType &type) override;
   void visit (TyTy::ADTType &type) override;
   void visit (TyTy::PlaceholderType &type) override;