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, 9 insertions, 0 deletions

diff --git a/gcc/rust/backend/rust-compile-var-decl.h b/gcc/rust/backend/rust-compile-var-decl.h
index a5c736d..4b52dcd 100644
--- a/gcc/rust/backend/rust-compile-var-decl.h
+++ b/gcc/rust/backend/rust-compile-var-decl.h
@@ -64,6 +64,15 @@ public:
 					     address_taken, locus);
   }
 
+  void visit (HIR::WildcardPattern &pattern) override
+  {
+    translated_type = ctx->get_backend ()->immutable_type (translated_type);
+    compiled_variable
+      = ctx->get_backend ()->local_variable (fndecl, "_", translated_type,
+					     NULL /*decl_var*/, address_taken,
+					     locus);
+  }
+
 private:
   CompileVarDecl (Context *ctx, tree fndecl)
     : HIRCompileBase (ctx), fndecl (fndecl),