Add mutablity checks and left hand size assignee checker

In order to assign to a name we must ensure the LHS is a valid expression
to assign to. This leads onto actually checking if this is a mutable
declaration or not.

Once these checks pass the name resolver we can in GIMPLE create immutable
types for these declarations to help with optimization.

Fixes #77

3 files changed, 81 insertions, 7 deletions

diff --git a/gcc/rust/backend/rust-compile-fnparam.h b/gcc/rust/backend/rust-compile-fnparam.h
new file mode 100644
index 0000000..cf6e6f7
--- /dev/null
+++ b/gcc/rust/backend/rust-compile-fnparam.h
@@ -0,0 +1,67 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+
+// This file is part of GCC.
+
+// GCC is free software; you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free
+// Software Foundation; either version 3, or (at your option) any later
+// version.
+
+// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+// for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with GCC; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#ifndef RUST_COMPILE_FNPARAM
+#define RUST_COMPILE_FNPARAM
+
+#include "rust-compile-base.h"
+
+namespace Rust {
+namespace Compile {
+
+class CompileFnParam : public HIRCompileBase
+{
+public:
+  static Bvariable *compile (Context *ctx, Bfunction *fndecl,
+			     HIR::FunctionParam *param, Btype *decl_type,
+			     Location locus)
+  {
+    CompileFnParam compiler (ctx, fndecl, decl_type, locus);
+    param->get_param_name ()->accept_vis (compiler);
+    return compiler.translated;
+  }
+
+  void visit (HIR::IdentifierPattern &pattern)
+  {
+    if (!pattern.is_mut)
+      decl_type = ctx->get_backend ()->immutable_type (decl_type);
+
+    translated
+      = ctx->get_backend ()->parameter_variable (fndecl, pattern.variable_ident,
+						 decl_type,
+						 false /* address_taken */,
+						 locus);
+  }
+
+private:
+  CompileFnParam (Context *ctx, ::Bfunction *fndecl, ::Btype *decl_type,
+		  Location locus)
+    : HIRCompileBase (ctx), fndecl (fndecl), decl_type (decl_type),
+      locus (locus), translated (nullptr)
+  {}
+
+  ::Bfunction *fndecl;
+  ::Btype *decl_type;
+  Location locus;
+  ::Bvariable *translated;
+};
+
+} // namespace Compile
+} // namespace Rust
+
+#endif // RUST_COMPILE_FNPARAM
diff --git a/gcc/rust/backend/rust-compile-item.h b/gcc/rust/backend/rust-compile-item.h
index bf899d8..1bb7c91 100644
--- a/gcc/rust/backend/rust-compile-item.h
+++ b/gcc/rust/backend/rust-compile-item.h
@@ -24,6 +24,7 @@
 #include "rust-compile-var-decl.h"
 #include "rust-compile-stmt.h"
 #include "rust-compile-expr.h"
+#include "rust-compile-fnparam.h"
 
 namespace Rust {
 namespace Compile {
@@ -174,17 +175,20 @@ public:
     for (auto &it : fntype->get_params ())
       {
 	HIR::FunctionParam &referenced_param = function.function_params.at (i);
-	auto param_pattern = it.first;
 	auto param_tyty = it.second;
-
 	auto compiled_param_type
 	  = TyTyResolveCompile::compile (ctx, param_tyty);
 
-	bool tree_addressable = false;
-	auto compiled_param_var = ctx->get_backend ()->parameter_variable (
-	  fndecl, param_pattern->as_string (), compiled_param_type,
-	  tree_addressable,
-	  ctx->get_mappings ()->lookup_location (param_tyty->get_ref ()));
+	Location param_locus
+	  = ctx->get_mappings ()->lookup_location (param_tyty->get_ref ());
+	Bvariable *compiled_param_var
+	  = CompileFnParam::compile (ctx, fndecl, &referenced_param,
+				     compiled_param_type, param_locus);
+	if (compiled_param_var == nullptr)
+	  {
+	    rust_error_at (param_locus, "failed to compile parameter variable");
+	    return;
+	  }
 
 	param_vars.push_back (compiled_param_var);
 
diff --git a/gcc/rust/backend/rust-compile-var-decl.h b/gcc/rust/backend/rust-compile-var-decl.h
index cf73820..06ea5a9 100644
--- a/gcc/rust/backend/rust-compile-var-decl.h
+++ b/gcc/rust/backend/rust-compile-var-decl.h
@@ -54,6 +54,9 @@ public:
 
   void visit (HIR::IdentifierPattern &pattern)
   {
+    if (!pattern.is_mut)
+      translated_type = ctx->get_backend ()->immutable_type (translated_type);
+
     translated
       = ctx->get_backend ()->local_variable (fndecl, pattern.variable_ident,
 					     translated_type, NULL /*decl_var*/,