auto merge of #16059 : epdtry/rust/mono-item-dedup, r=alexcrichton

Currently, each time a function is monomorphized, all items within that function are translated.  This is unnecessary work because the inner items already get translated when the function declaration is visited by `trans_item`.  This patch adds a flag to the `FunctionContext` to prevent translation of items during monomorphization.

src/test/run-make/issue-7349/Makefile

@@ -0,0 +1,11 @@
+-include ../tools.mk
+
+# Test to make sure that inner functions within a polymorphic outer function
+# don't get re-translated when the outer function is monomorphized.  The test
+# code monomorphizes the outer function several times, but the magic constant
+# `8675309` used in the inner function should appear only once in the generated
+# IR.
+
+all:
+	$(RUSTC) foo.rs --emit=ir
+	[ "$$(grep -c 8675309 "$(TMPDIR)/foo.ll")" -eq "1" ]

src/test/run-make/issue-7349/foo.rs

@@ -0,0 +1,21 @@
+// 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.
+
+fn outer<T>() {
+    #[allow(dead_code)]
+    fn inner() -> uint {
+        8675309
+    }
+}
+
+fn main() {
+    outer::<int>();
+    outer::<uint>();
+}