gccrs: fix unconstrained infer vars on generic associated type

The trick here is that when Bar::test is resolved it resolves to the
trait method:

  fn <Bar<i32>, T> (placeholder) -> placeholder

Which is fine so we need to setup the associated types for Bar<i32> which
means looking up the associated impl block then setting up the projection
of A = T so it becomes:

  fn <Bar<i32>, T> (placeholder: projection<T>:T)
    -> placeholder: projection<T>:T

But previously it was auto injecting inference variables so it became:

  fn <Bar<i32>, T> (placeholder: projection<T>:?T)
    -> placeholder: projection<T>:?T

The issue is that the binding of the generics was still T so this caused
inference variables to be injected again but unlinked. A possible tweak
would be that we are substituting again with new infer vars to actually
just unify them enplace so they are all part of the chain. This still
might be needed but lets hold off for now.

So basically when we are Path probing we dont allow GAT's to generate new
inference vars because they wont be bound to this current segment which
just causes confusion.

Fixes Rust-GCC#3242

gcc/rust/ChangeLog:

	* typecheck/rust-hir-trait-reference.h: add default infer arg
	* typecheck/rust-hir-trait-resolve.cc: dont add new infer vars
	* typecheck/rust-hir-type-check-path.cc (TypeCheckExpr::resolve_segments): dont infer

gcc/testsuite/ChangeLog:

	* rust/compile/issue-3242.rs: no longer skip the test

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

diff --git a/gcc/rust/typecheck/rust-hir-trait-reference.h b/gcc/rust/typecheck/rust-hir-trait-reference.h
index 307dca47160795eab7bddd95b6a39e86c103b36c..5866a2334cd5b4d49e8ae34ba39faea5e4ba2a36 100644 (file)
--- a/gcc/rust/typecheck/rust-hir-trait-reference.h
+++ b/gcc/rust/typecheck/rust-hir-trait-reference.h
@@ -254,10 +254,9 @@ public:
 
   void setup_raw_associated_types ();
 
-  TyTy::BaseType *
-  setup_associated_types (const TyTy::BaseType *self,
-                         const TyTy::TypeBoundPredicate &bound,
-                         TyTy::SubstitutionArgumentMappings *args = nullptr);
+  TyTy::BaseType *setup_associated_types (
+    const TyTy::BaseType *self, const TyTy::TypeBoundPredicate &bound,
+    TyTy::SubstitutionArgumentMappings *args = nullptr, bool infer = true);
 
   void reset_associated_types ();
 

diff --git a/gcc/rust/typecheck/rust-hir-trait-resolve.cc b/gcc/rust/typecheck/rust-hir-trait-resolve.cc
index 71ae7dfe6ab445340550a0355aae160bb3fb6a0c..811abcbaeea4f52aefb5591239c7eaca99559068 100644 (file)
--- a/gcc/rust/typecheck/rust-hir-trait-resolve.cc
+++ b/gcc/rust/typecheck/rust-hir-trait-resolve.cc
@@ -485,7 +485,7 @@ AssociatedImplTrait::setup_raw_associated_types ()
 TyTy::BaseType *
 AssociatedImplTrait::setup_associated_types (
   const TyTy::BaseType *self, const TyTy::TypeBoundPredicate &bound,
-  TyTy::SubstitutionArgumentMappings *args)
+  TyTy::SubstitutionArgumentMappings *args, bool infer)
 {
   // compute the constrained impl block generic arguments based on self and the
   // higher ranked trait bound
@@ -545,7 +545,7 @@ AssociatedImplTrait::setup_associated_types (
   std::vector<TyTy::SubstitutionArg> subst_args;
   for (auto &p : substitutions)
     {
-      if (p.needs_substitution ())
+      if (p.needs_substitution () && infer)
        {
          TyTy::TyVar infer_var = TyTy::TyVar::get_implicit_infer_var (locus);
          subst_args.push_back (
@@ -619,7 +619,7 @@ AssociatedImplTrait::setup_associated_types (
        = unify_site_and (a->get_ref (), TyTy::TyWithLocation (a),
                          TyTy::TyWithLocation (b), impl_predicate.get_locus (),
                          true /*emit-errors*/, true /*commit-if-ok*/,
-                         false /*infer*/, true /*cleanup-on-fail*/);
+                         true /*infer*/, true /*cleanup-on-fail*/);
       rust_assert (result->get_kind () != TyTy::TypeKind::ERROR);
     }
 
@@ -632,7 +632,7 @@ AssociatedImplTrait::setup_associated_types (
                                TyTy::TyWithLocation (impl_self_infer),
                                impl_predicate.get_locus (),
                                true /*emit-errors*/, true /*commit-if-ok*/,
-                               false /*infer*/, true /*cleanup-on-fail*/);
+                               true /*infer*/, true /*cleanup-on-fail*/);
   rust_assert (result->get_kind () != TyTy::TypeKind::ERROR);
   TyTy::BaseType *self_result = result;
 

diff --git a/gcc/rust/typecheck/rust-hir-type-check-path.cc b/gcc/rust/typecheck/rust-hir-type-check-path.cc
index 1904eba0c19469e9651a8cd99c593cbcf07cd065..74ab1414e5840c8d8ab2a4565f50dce152791c74 100644 (file)
--- a/gcc/rust/typecheck/rust-hir-type-check-path.cc
+++ b/gcc/rust/typecheck/rust-hir-type-check-path.cc
@@ -535,8 +535,8 @@ TypeCheckExpr::resolve_segments (NodeId root_resolved_node_id,
                = impl_block_ty->lookup_predicate (trait_ref.get_defid ());
              if (!predicate.is_error ())
                impl_block_ty
-                 = associated->setup_associated_types (prev_segment,
-                                                       predicate);
+                 = associated->setup_associated_types (prev_segment, predicate,
+                                                       nullptr, false);
            }
        }
 

diff --git a/gcc/testsuite/rust/compile/issue-3242.rs b/gcc/testsuite/rust/compile/issue-3242.rs
index 468497a4792ef56e5ad64292fccbf63a5b5de16e..a4542aea00b080fef10c3615879529067850d2ad 100644 (file)
--- a/gcc/testsuite/rust/compile/issue-3242.rs
+++ b/gcc/testsuite/rust/compile/issue-3242.rs
@@ -1,5 +1,4 @@
 #[lang = "sized"]
-// { dg-skip-if "" { *-*-* } }
 pub trait Sized {}
 
 trait Foo<T> {