Fix type unification for Inference Variables and return types

When we resolve the type of an expression such as a LiteralExpr with HIR id
10, but is the final expression in a BlockExpr of HirId 11. The same type
is infered for the entire BlockExpr as well as the final Expr but we
override the reference id on the TyTy::Type. This means if there is a
change in reference id the old ID must be added to the combined reference
chain for type inference to take place.

Fixes #293

2 files changed, 13 insertions, 1 deletions

diff --git a/gcc/rust/typecheck/rust-tyty.h b/gcc/rust/typecheck/rust-tyty.h
index 9fe7417..2d97a0b 100644
--- a/gcc/rust/typecheck/rust-tyty.h
+++ b/gcc/rust/typecheck/rust-tyty.h
@@ -57,7 +57,12 @@ public:
 
   HirId get_ref () const { return ref; }
 
-  void set_ref (HirId id) { ref = id; }
+  void set_ref (HirId id)
+  {
+    if (id != ref)
+      append_reference (ref);
+    ref = id;
+  }
 
   HirId get_ty_ref () const { return ty_ref; }
 
diff --git a/gcc/testsuite/rust.test/compilable/block_expr4.rs b/gcc/testsuite/rust.test/compilable/block_expr4.rs
new file mode 100644
index 0000000..35a5cd0
--- /dev/null
+++ b/gcc/testsuite/rust.test/compilable/block_expr4.rs
@@ -0,0 +1,7 @@
+fn foo() -> isize {
+    0
+}
+
+fn main() {
+    let a = foo();
+}