Updated metadata::creader::resolve_crate_deps to use the correct span. Clarified error message when an external crate's dependency is missing. Closes #2404.

src/test/run-make/missing-crate-dependency/Makefile

@@ -0,0 +1,9 @@
+-include ../tools.mk
+
+all: 
+	$(RUSTC) --crate-type=rlib crateA.rs
+	$(RUSTC) --crate-type=rlib crateB.rs
+	rm $(TMPDIR)/$(call RLIB_GLOB,crateA)
+	# Ensure crateC fails to compile since dependency crateA is missing
+	$(RUSTC) crateC.rs 2>&1 | \
+		grep "error: can't find crate for \`crateA\` which \`crateB\` depends on"

src/test/run-make/missing-crate-dependency/crateA.rs

@@ -0,0 +1,12 @@
+// 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.
+
+// Base crate
+pub fn func() {}

src/test/run-make/missing-crate-dependency/crateB.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.
+
+extern crate crateA;

src/test/run-make/missing-crate-dependency/crateC.rs

@@ -0,0 +1,13 @@
+// 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.
+
+extern crate crateB;
+
+fn main() {}