Properly adjust filenames when multiple emissions

Fixes rust-lang#40993

Author: nagisa

src/librustc_driver/driver.rs

@@ -1358,10 +1358,9 @@ pub fn build_output_filenames(input: &Input,
                                            .values()
                                            .filter(|a| a.is_none())
                                            .count();
-            let ofile = if unnamed_output_types > 1 &&
-                            sess.opts.output_types.contains_key(&OutputType::Exe) {
-                sess.warn("ignoring specified output filename for 'link' output because multiple \
-                           outputs were requested");
+            let ofile = if unnamed_output_types > 1 {
+                sess.warn("due to multiple output types requested, the explicitly specified \
+                           output file name will be adapted for each output type");
                 None
             } else {
                 Some(out_file.clone())

src/test/run-make/multiple-emits/Makefile

@@ -0,0 +1,7 @@
+-include ../tools.mk
+
+all:
+	$(RUSTC) foo.rs --emit=asm,llvm-ir -o $(TMPDIR)/out 2>&1
+	rm $(TMPDIR)/out.ll $(TMPDIR)/out.s
+	$(RUSTC) foo.rs --emit=asm,llvm-ir -o $(TMPDIR)/out2.ext 2>&1
+	rm $(TMPDIR)/out2.ll $(TMPDIR)/out2.s

src/test/run-make/multiple-emits/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.
+
+fn main() {}