correct fully qualified type names to include the crate; add tests

fixes #1745

Author: nikomatsakis

src/comp/metadata/csearch.rs

@@ -60,7 +60,8 @@ fn resolve_path(cstore: cstore::cstore, cnum: ast::crate_num,
 fn get_item_path(tcx: ty::ctxt, def: ast::def_id) -> ast_map::path {
     let cstore = tcx.sess.cstore;
     let cdata = cstore::get_crate_data(cstore, def.crate);
-    ret decoder::get_item_path(cdata, def.node);
+    let path = decoder::get_item_path(cdata, def.node);
+    [ast_map::path_mod(cdata.name)] + path
 }
 
 fn get_enum_variants(tcx: ty::ctxt, def: ast::def_id) -> [ty::variant_info] {

src/comp/middle/ast_map.rs

@@ -17,7 +17,7 @@ fn path_to_str_with_sep(p: path, sep: str) -> str {
 }
 
 fn path_to_str(p: path) -> str {
-    path_to_str_with_sep(p, "::")
+    "::" + path_to_str_with_sep(p, "::")
 }
 
 enum ast_node {

src/test/compile-fail/fully-qualified-type-name1.rs

@@ -0,0 +1,7 @@
+// Test that we use fully-qualified type names in error messages.
+
+fn main() {
+    let x: option<uint>;
+    x = 5;
+    //!^ ERROR mismatched types: expected `::core::option::t<uint>`
+}

src/test/compile-fail/fully-qualified-type-name2.rs

@@ -0,0 +1,17 @@
+// Test that we use fully-qualified type names in error messages.
+
+mod x {
+    enum foo { }
+}
+
+mod y {
+    enum foo { }
+}
+
+fn bar(x: x::foo) -> y::foo {
+    ret x;
+    //!^ ERROR mismatched types: expected `::y::foo` but found `::x::foo`
+}
+
+fn main() {
+}