mir-opt tests: add ability to match lines that contain the filename

src/test/mir-opt/README.md

@@ -21,9 +21,10 @@ The test format is:
 All the test information is in comments so the test is runnable.
 
 For each $file_name, compiletest expects [$expected_line_0, ...,
-$expected_line_N] to appear in the dumped MIR in order.  Currently it allows
-other non-matched lines before, after and in-between. Note that this includes
-lines that end basic blocks or begin new ones; it is good practice
+$expected_line_N] to appear in the dumped MIR in order. Every occurrence of `$FILE`
+in the expected line is replaced with the file name of the source code before
+matching.  Currently it allows other non-matched lines before, after and in-between.
+Note that this includes lines that end basic blocks or begin new ones; it is good practice
 in your tests to include the terminator for each of your basic blocks as an
 internal sanity check guarding against a test like:
 

src/test/mir-opt/filename.rs

@@ -0,0 +1,22 @@
+// Copyright 2012-2016 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.
+
+// Check that we can write tests for lines that contain the filename of the test
+
+fn main() {
+    let closure = |x: i32| x+x;
+    closure(21);
+}
+
+// END RUST SOURCE
+// START rustc.node15.EraseRegions.after.mir
+// fn main::{{closure}}(_1: &[closure@$FILE:14:19: 14:31], _2: i32) -> i32 {
+// }
+// END rustc.node15.EraseRegions.after.mir

src/tools/compiletest/src/runtest.rs

@@ -2300,6 +2300,7 @@ actual:\n\
                                                    .read_to_string(&mut test_file_contents)
                                                    .unwrap();
         if let Some(idx) =  test_file_contents.find("// END RUST SOURCE") {
+            let filename = self.testpaths.file.to_str().unwrap();
             let (_, tests_text) = test_file_contents.split_at(idx + "// END_RUST SOURCE".len());
             let tests_text_str = String::from(tests_text);
             let mut curr_test : Option<&str> = None;
@@ -2321,7 +2322,7 @@ actual:\n\
                     // ignore
                 } else if l.starts_with("// ") {
                     let (_, test_content) = l.split_at("// ".len());
-                    curr_test_contents.push(test_content);
+                    curr_test_contents.push(test_content.replace("$FILE", filename));
                 }
             }
         }
@@ -2339,7 +2340,7 @@ actual:\n\
         }
     }
 
-    fn compare_mir_test_output(&self, test_name: &str, expected_content: &[&str]) {
+    fn compare_mir_test_output(&self, test_name: &str, expected_content: &[String]) {
         let mut output_file = PathBuf::new();
         output_file.push(self.get_mir_dump_dir());
         output_file.push(test_name);