Add support for Wildcard pattern binding

Wildcard bindings allow us to bind expression to be unused such as:

  let _ = 123;

They are more commonly used in destructuring of tuples such as:

  let my_tuple = (1,2);
  let (a,_) = my_tuple;

This is the initial basic support for the basic form of let _ = ...; and
it also allows us to ignore parameters within functions as well.

Fixes #557

1 files changed, 11 insertions, 0 deletions

diff --git a/gcc/rust/resolve/rust-ast-resolve-pattern.h b/gcc/rust/resolve/rust-ast-resolve-pattern.h
index 57c73ba..01a0534 100644
--- a/gcc/rust/resolve/rust-ast-resolve-pattern.h
+++ b/gcc/rust/resolve/rust-ast-resolve-pattern.h
@@ -83,6 +83,17 @@ public:
 				    pattern.get_is_mut ());
   }
 
+  void visit (AST::WildcardPattern &pattern) override
+  {
+    resolver->get_name_scope ().insert (
+      CanonicalPath::new_seg (pattern.get_node_id (), "_"),
+      pattern.get_node_id (), pattern.get_locus ());
+    resolver->insert_new_definition (pattern.get_node_id (),
+				     Definition{pattern.get_node_id (),
+						parent});
+    resolver->mark_decl_mutability (pattern.get_node_id (), false);
+  }
+
   // cases in a match expression
   void visit (AST::PathInExpression &pattern) override;