Tweak and add test for detecting libraries with mismatching target triples.

Closes #10814.

Author: huonw

Diff for: src/librustc/metadata/loader.rs

@@ -307,7 +307,8 @@ impl<'a> Context<'a> {
             format!("found possibly newer version of crate `{}`",
                     self.ident)
         } else if self.rejected_via_triple.len() > 0 {
-            format!("found incorrect triple for crate `{}`", self.ident)
+            format!("couldn't find crate `{}` with expected target triple {}",
+                    self.ident, self.triple)
         } else {
             format!("can't find crate for `{}`", self.ident)
         };
@@ -318,15 +319,12 @@ impl<'a> Context<'a> {
         };
         self.sess.span_err(self.span, message.as_slice());
 
-        let mismatches = self.rejected_via_triple.iter();
         if self.rejected_via_triple.len() > 0 {
-            self.sess.span_note(self.span,
-                                format!("expected triple of {}",
-                                        self.triple).as_slice());
+            let mismatches = self.rejected_via_triple.iter();
             for (i, &CrateMismatch{ ref path, ref got }) in mismatches.enumerate() {
                 self.sess.fileline_note(self.span,
-                    format!("crate `{}` path {}{}, triple {}: {}",
-                            self.ident, "#", i+1, got, path.display()).as_slice());
+                    format!("crate `{}`, path #{}, triple {}: {}",
+                            self.ident, i+1, got, path.display()).as_slice());
             }
         }
         if self.rejected_via_hash.len() > 0 {

Diff for: src/test/run-make/mismatching-target-triples/Makefile

@@ -0,0 +1,11 @@
+-include ../tools.mk
+
+# Issue #10814
+#
+# these are no_std to avoid having to have the standard library or any
+# linkers/assemblers for the relevant platform
+
+all:
+	$(RUSTC) foo.rs --target=i686-unknown-linux-gnu
+	$(RUSTC) bar.rs --target=x86_64-unknown-linux-gnu 2>&1 \
+		| grep "couldn't find crate .foo. with expected target triple x86_64-unknown-linux-gnu"

Diff for: src/test/run-make/mismatching-target-triples/bar.rs

@@ -0,0 +1,11 @@
+// Copyright 2014 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.
+#![no_std]
+extern crate foo;

Diff for: src/test/run-make/mismatching-target-triples/foo.rs

@@ -0,0 +1,11 @@
+// Copyright 2014 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.
+#![no_std]
+#![crate_type = "lib"]