[gcc r15-8791] gccrs: remove bad type checking diagnostic

[Arthur Cohen]

https://gcc.gnu.org/g:a34f4d5a817f777696a0b0ddf1328275c8a81538

commit r15-8791-ga34f4d5a817f777696a0b0ddf1328275c8a81538
Author: Philip Herron <herron.philip@googlemail.com>
Date:   Tue Feb 4 17:15:15 2025 +0000

    gccrs: remove bad type checking diagnostic
    
    This was a bad diagnostic added when I was working on slices and iterators
    also the name of the function is also bad. This is all about setting up
    associated types based on the current context of the bounds assocated with
    the associated trait bounds on this function.
    
    The tell tale is that this didnt have an associated rust error code so
    this is most definetly not the correct error diagnostic.
    
    Fixes Rust-GCC#3403
    
    gcc/rust/ChangeLog:
    
            * typecheck/rust-tyty-subst.cc (SubstitutionRef::monomorphize): remove diagnostic
    
    gcc/testsuite/ChangeLog:
    
            * rust/compile/nr2/exclude: nr2 cant handle this
            * rust/compile/issue-3403.rs: New test.
    
    Signed-off-by: Philip Herron <herron.philip@googlemail.com>

Diff:
---
 gcc/rust/typecheck/rust-tyty-subst.cc    | 21 +-----------------
 gcc/testsuite/rust/compile/issue-3403.rs | 38 ++++++++++++++++++++++++++++++++
 gcc/testsuite/rust/compile/nr2/exclude   |  1 +
 3 files changed, 40 insertions(+), 20 deletions(-)

diff --git a/gcc/rust/typecheck/rust-tyty-subst.cc b/gcc/rust/typecheck/rust-tyty-subst.cc
index a12ad91192d3..eb9e9dc92783 100644
--- a/gcc/rust/typecheck/rust-tyty-subst.cc
+++ b/gcc/rust/typecheck/rust-tyty-subst.cc
@@ -934,27 +934,8 @@ SubstitutionRef::monomorphize ()
 	  auto associated
 	    = Resolver::lookup_associated_impl_block (bound, binding,
 						      &ambigious);
-	  if (associated == nullptr && ambigious)
-	    {
-	      // go for the first one? or error out?
-	      auto &mappings = Analysis::Mappings::get ();
-	      const auto &type_param = subst.get_generic_param ();
-	      const auto *trait_ref = bound.get ();
-
-	      rich_location r (line_table, type_param.get_locus ());
-	      r.add_range (bound.get_locus ());
-	      r.add_range (mappings.lookup_location (binding->get_ref ()));
-
-	      rust_error_at (r, "ambiguous type bound for trait %s and type %s",
-			     trait_ref->get_name ().c_str (),
-			     binding->get_name ().c_str ());
-	      return false;
-	    }
-
 	  if (associated != nullptr)
-	    {
-	      associated->setup_associated_types (binding, bound);
-	    }
+	    associated->setup_associated_types (binding, bound);
 	}
     }
 
diff --git a/gcc/testsuite/rust/compile/issue-3403.rs b/gcc/testsuite/rust/compile/issue-3403.rs
new file mode 100644
index 000000000000..ced6b4efd975
--- /dev/null
+++ b/gcc/testsuite/rust/compile/issue-3403.rs
@@ -0,0 +1,38 @@
+pub struct Foo {
+    a: i32,
+    // { dg-warning "field is never read" "" { target *-*-* } .-1 }
+}
+pub struct Bar(i32);
+
+#[lang = "sized"]
+trait Sized {}
+
+pub mod core {
+    pub mod default {
+        pub trait Default: Sized {
+            fn default() -> Self;
+        }
+
+        impl Default for i32 {
+            fn default() -> Self {
+                0
+            }
+        }
+    }
+}
+
+impl ::core::default::Default for Bar {
+    #[inline]
+    fn default() -> Bar {
+        Bar(core::default::Default::default())
+    }
+}
+
+impl ::core::default::Default for Foo {
+    #[inline]
+    fn default() -> Foo {
+        Foo {
+            a: core::default::Default::default(),
+        }
+    }
+}
diff --git a/gcc/testsuite/rust/compile/nr2/exclude b/gcc/testsuite/rust/compile/nr2/exclude
index 512419438db6..6f6280d3b661 100644
--- a/gcc/testsuite/rust/compile/nr2/exclude
+++ b/gcc/testsuite/rust/compile/nr2/exclude
@@ -123,4 +123,5 @@ derive-default1.rs
 issue-3402-1.rs
 for-loop1.rs
 for-loop2.rs
+issue-3403.rs
 # please don't delete the trailing newline