gccrs: resolve the associated_predicate when mapping Fn traits

This is required to solve #2105

gcc/rust/ChangeLog:

	* typecheck/rust-hir-type-check-expr.cc (TypeCheckExpr::resolve_fn_trait_call):
	return the assoicated predicate
	* typecheck/rust-hir-type-check-expr.h: update prototype

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

2 files changed, 12 insertions, 6 deletions

diff --git a/gcc/rust/typecheck/rust-hir-type-check-expr.cc b/gcc/rust/typecheck/rust-hir-type-check-expr.cc
index 704ca2b9e5b..8d2e89ba0d7 100644
--- a/gcc/rust/typecheck/rust-hir-type-check-expr.cc
+++ b/gcc/rust/typecheck/rust-hir-type-check-expr.cc
@@ -1784,7 +1784,7 @@ TypeCheckExpr::resolve_operator_overload (
 
 HIR::PathIdentSegment
 TypeCheckExpr::resolve_possible_fn_trait_call_method_name (
-  const TyTy::BaseType &receiver)
+  TyTy::BaseType &receiver, TyTy::TypeBoundPredicate *associated_predicate)
 {
   // Question
   // do we need to probe possible bounds here? I think not, i think when we
@@ -1793,7 +1793,7 @@ TypeCheckExpr::resolve_possible_fn_trait_call_method_name (
   // FIXME
   // the logic to map the FnTrait to their respective call trait-item is
   // duplicated over in the backend/rust-compile-expr.cc
-  for (const auto &bound : receiver.get_specified_bounds ())
+  for (auto &bound : receiver.get_specified_bounds ())
     {
       bool found_fn = bound.get_name ().compare ("Fn") == 0;
       bool found_fn_mut = bound.get_name ().compare ("FnMut") == 0;
@@ -1801,19 +1801,23 @@ TypeCheckExpr::resolve_possible_fn_trait_call_method_name (
 
       if (found_fn)
 	{
+	  *associated_predicate = bound;
 	  return HIR::PathIdentSegment ("call");
 	}
       else if (found_fn_mut)
 	{
+	  *associated_predicate = bound;
 	  return HIR::PathIdentSegment ("call_mut");
 	}
       else if (found_fn_once)
 	{
+	  *associated_predicate = bound;
 	  return HIR::PathIdentSegment ("call_once");
 	}
     }
 
   // nothing
+  *associated_predicate = TyTy::TypeBoundPredicate::error ();
   return HIR::PathIdentSegment ("");
 }
 
@@ -1823,9 +1827,11 @@ TypeCheckExpr::resolve_fn_trait_call (HIR::CallExpr &expr,
 				      TyTy::BaseType **result)
 {
   // we turn this into a method call expr
+  auto associated_predicate = TyTy::TypeBoundPredicate::error ();
   HIR::PathIdentSegment method_name
-    = resolve_possible_fn_trait_call_method_name (*receiver_tyty);
-  if (method_name.is_error ())
+    = resolve_possible_fn_trait_call_method_name (*receiver_tyty,
+						  &associated_predicate);
+  if (method_name.is_error () || associated_predicate.is_error ())
     return false;
 
   auto candidates = MethodResolver::Probe (receiver_tyty, method_name);
diff --git a/gcc/rust/typecheck/rust-hir-type-check-expr.h b/gcc/rust/typecheck/rust-hir-type-check-expr.h
index 5be9bcdb3f1..1a9591f1d49 100644
--- a/gcc/rust/typecheck/rust-hir-type-check-expr.h
+++ b/gcc/rust/typecheck/rust-hir-type-check-expr.h
@@ -97,8 +97,8 @@ protected:
 			      TyTy::BaseType *function_tyty,
 			      TyTy::BaseType **result);
 
-  HIR::PathIdentSegment
-  resolve_possible_fn_trait_call_method_name (const TyTy::BaseType &receiver);
+  HIR::PathIdentSegment resolve_possible_fn_trait_call_method_name (
+    TyTy::BaseType &receiver, TyTy::TypeBoundPredicate *associated_predicate);
 
 private:
   TypeCheckExpr ();