Fix issue #8763

* added case & better error message for "impl trait for module"
* used better way to print the module
* switched from //error-pattern to //~ ERROR
* added compile-fail test trait-impl-for-module.rs
* revised compile-fail test trait-or-new-type-instead
    (the error message for the modified test is still unclear, but that's a different bug)
* added FIXME to trait-or-new-type-instead

src/librustc/middle/typeck/astconv.rs

@@ -1,4 +1,4 @@
-// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //
@@ -60,10 +60,11 @@ use middle::typeck::lookup_def_tcx;
 
 use std::vec;
 use syntax::abi::AbiSet;
-use syntax::{ast, ast_util};
+use syntax::{ast, ast_map, ast_util};
 use syntax::codemap::Span;
 use syntax::opt_vec::OptVec;
 use syntax::opt_vec;
+use syntax::parse::token;
 use syntax::print::pprust::{lifetime_to_str, path_to_str};
 
 pub trait AstConv {
@@ -518,6 +519,12 @@ pub fn ast_ty_to_ty<AC:AstConv, RS:RegionScope>(
             let did = ast_util::local_def(id);
             ty::mk_self(tcx, did)
           }
+          ast::DefMod(id) => {
+            tcx.sess.span_fatal(ast_ty.span,
+                                format!("found module name used as a type: {}",
+                                        ast_map::node_id_to_str(tcx.items, id.node,
+                                        token::get_ident_interner())));
+          }
           _ => {
             tcx.sess.span_fatal(ast_ty.span,
                                 format!("found value name used as a type: {:?}", a_def));

src/test/compile-fail/trait-impl-for-module.rs

@@ -0,0 +1,21 @@
+// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+mod a {
+}
+
+trait A {
+}
+
+impl A for a { //~ERROR found module name used as a type
+}
+
+fn main() {
+}

src/test/compile-fail/trait-or-new-type-instead.rs

@@ -1,4 +1,4 @@
-// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //
@@ -8,8 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// error-pattern: found value name used as a type
-impl<T> Option<T> {
+// FIXME(#8767) bad error message; Option is not a module
+impl<T> Option<T> { //~ERROR found module name used as a type
     pub fn foo(&self) { }
 }