From: Philip Herron <herron.philip@googlemail.com>
Date: Mon, 4 Nov 2024 14:43:25 +0000 (+0000)
Subject: gccrs: fix bad type inference on local patterns
X-Git-Tag: basepoints/gcc-16~1041
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=389756b2ac97beeb72cd160eeefee5ea381e55e9;p=thirdparty%2Fgcc.git

gccrs: fix bad type inference on local patterns

We do not need to inject inference variables on generic patterns
with generic blocks. This will just cause unconstrained inference
variables as they may not unify against something.

Fixes Rust-GCC#2323

gcc/rust/ChangeLog:

	* typecheck/rust-hir-type-check-path.cc (TypeCheckExpr::resolve_root_path): dont infer here

gcc/testsuite/ChangeLog:

	* rust/compile/nr2/exclude: nr2 cant handle this
	* rust/compile/issue-2323.rs: New test.

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

diff --git a/gcc/rust/typecheck/rust-hir-type-check-path.cc b/gcc/rust/typecheck/rust-hir-type-check-path.cc
index 231ddd604db..7b934b38eb3 100644
--- a/gcc/rust/typecheck/rust-hir-type-check-path.cc
+++ b/gcc/rust/typecheck/rust-hir-type-check-path.cc
@@ -245,6 +245,7 @@ TypeCheckExpr::resolve_root_path (HIR::PathInExpression &expr, size_t *offset,
 
       auto seg_is_module = mappings.lookup_module (ref).has_value ();
       auto seg_is_crate = mappings.is_local_hirid_crate (ref);
+      auto seg_is_pattern = mappings.lookup_hir_pattern (ref).has_value ();
       if (seg_is_module || seg_is_crate)
 	{
 	  // A::B::C::this_is_a_module::D::E::F
@@ -321,7 +322,7 @@ TypeCheckExpr::resolve_root_path (HIR::PathInExpression &expr, size_t *offset,
 	  if (lookup->get_kind () == TyTy::TypeKind::ERROR)
 	    return new TyTy::ErrorType (expr.get_mappings ().get_hirid ());
 	}
-      else if (lookup->needs_generic_substitutions ())
+      else if (lookup->needs_generic_substitutions () && !seg_is_pattern)
 	{
 	  lookup = SubstMapper::InferSubst (lookup, expr.get_locus ());
 	}
diff --git a/gcc/testsuite/rust/compile/issue-2323.rs b/gcc/testsuite/rust/compile/issue-2323.rs
new file mode 100644
index 00000000000..02a3f90b4d8
--- /dev/null
+++ b/gcc/testsuite/rust/compile/issue-2323.rs
@@ -0,0 +1,9 @@
+#[lang = "sized"]
+trait Sized {}
+
+pub struct S<T>(T);
+
+pub fn foo<T>(x: T) {
+    let y = S(x);
+    y.0;
+}
diff --git a/gcc/testsuite/rust/compile/nr2/exclude b/gcc/testsuite/rust/compile/nr2/exclude
index 4ba27d31f88..eaa2a1e0d0b 100644
--- a/gcc/testsuite/rust/compile/nr2/exclude
+++ b/gcc/testsuite/rust/compile/nr2/exclude
@@ -222,4 +222,5 @@ if_let_expr_simple.rs
 iflet.rs
 issue-3033.rs
 issue-3009.rs
+issue-2323.rs
 # please don't delete the trailing newline