typecheck: Fix location and add help for E0044 foreign generics

gcc/rust/typecheck/rust-hir-type-check-base.cc

@@ -553,9 +553,14 @@ TypeCheckBase::resolve_generic_params (
 	  {
 	    if (is_foreign && abi != Rust::ABI::INTRINSIC)
 	      {
-		rust_error_at (generic_param->get_locus (), ErrorCode::E0044,
-			       "foreign items may not have const parameters");
-	      }
+			  rich_location r(line_table, generic_param->get_locus());
+			  rust_error_at(r, ErrorCode::E0044,
+							"foreign items may not have const parameters");
+
+			  rust_inform(
+				  generic_param->get_locus(),
+				  "replace the const parameters with concrete types");
+		  }
 
 	    auto &param
 	      = static_cast<HIR::ConstGenericParam &> (*generic_param);
@@ -627,9 +632,13 @@ TypeCheckBase::resolve_generic_params (
 	  {
 	    if (is_foreign && abi != Rust::ABI::INTRINSIC)
 	      {
-		rust_error_at (generic_param->get_locus (), ErrorCode::E0044,
-			       "foreign items may not have type parameters");
-	      }
+			  rich_location r(line_table, generic_param->get_locus());
+			  rust_error_at(r, ErrorCode::E0044,
+							"foreign items may not have type parameters");
+
+			  rust_inform(generic_param->get_locus(),
+						  "replace the type parameters with concrete types");
+		  }
 
 	    auto param_type = TypeResolveGenericParam::Resolve (
 	      *generic_param, false /*resolve_trait_bounds*/);

gcc/testsuite/rust/compile/issue-3526.rs

@@ -0,0 +1,8 @@
+// { dg-options "-w" }
+// { dg-excess-errors "Noisy error reporting" }
+extern "C" {
+    fn some_func<T>(x: T); // { dg-error "foreign items may not have type parameters" }
+    // { dg-message "replace the type parameters" "" { target *-*-* } .-1 }
+}
+
+fn main() {}