From c40fad34e25f4e00b118d7d362e7639954a717f2 Mon Sep 17 00:00:00 2001
From: "Felix S. Klock II" <pnkfelix@pnkfx.org>
Date: Fri, 28 Oct 2016 17:10:34 +0200
Subject: [PATCH 1/2] Debug instrumentation for construction of ImportedFileMap
 table entries.

---
 src/librustc_metadata/decoder.rs | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/librustc_metadata/decoder.rs b/src/librustc_metadata/decoder.rs
index 0d42ff8ce27..3e367cbee2e 100644
--- a/src/librustc_metadata/decoder.rs
+++ b/src/librustc_metadata/decoder.rs
@@ -1138,6 +1138,14 @@ pub fn imported_filemaps(&'a self,
 
                 match reusable_filemap {
                     Some(fm) => {
+
+                        debug!("CrateMetaData::imported_filemaps reuse \
+                                filemap {:?} original (start_pos {:?} end_pos {:?}) \
+                                translated (start_pos {:?} end_pos {:?})",
+                               filemap_to_import.name,
+                               filemap_to_import.start_pos, filemap_to_import.end_pos,
+                               fm.start_pos, fm.end_pos);
+
                         cstore::ImportedFileMap {
                             original_start_pos: filemap_to_import.start_pos,
                             original_end_pos: filemap_to_import.end_pos,
@@ -1176,6 +1184,12 @@ pub fn imported_filemaps(&'a self,
                                                                                source_length,
                                                                                lines,
                                                                                multibyte_chars);
+                        debug!("CrateMetaData::imported_filemaps alloc \
+                                filemap {:?} original (start_pos {:?} end_pos {:?}) \
+                                translated (start_pos {:?} end_pos {:?})",
+                               local_version.name, start_pos, end_pos,
+                               local_version.start_pos, local_version.end_pos);
+
                         cstore::ImportedFileMap {
                             original_start_pos: start_pos,
                             original_end_pos: end_pos,

From 3f639a0f11eda43d9a31ef407eaac793dd038a43 Mon Sep 17 00:00:00 2001
From: "Felix S. Klock II" <pnkfelix@pnkfx.org>
Date: Fri, 28 Oct 2016 17:12:54 +0200
Subject: [PATCH 2/2] Do not intern filemap to entry w/ mismatched length. Fix
 #37274 (I think).

---
 src/librustc_metadata/decoder.rs | 4 ++++
 src/libsyntax_pos/lib.rs         | 3 +++
 2 files changed, 7 insertions(+)

diff --git a/src/librustc_metadata/decoder.rs b/src/librustc_metadata/decoder.rs
index 3e367cbee2e..7f36fa59830 100644
--- a/src/librustc_metadata/decoder.rs
+++ b/src/librustc_metadata/decoder.rs
@@ -1207,6 +1207,10 @@ pub fn imported_filemaps(&'a self,
 }
 
 fn are_equal_modulo_startpos(fm1: &syntax_pos::FileMap, fm2: &syntax_pos::FileMap) -> bool {
+    if fm1.byte_length() != fm2.byte_length() {
+        return false;
+    }
+
     if fm1.name != fm2.name {
         return false;
     }
diff --git a/src/libsyntax_pos/lib.rs b/src/libsyntax_pos/lib.rs
index e3feaee5369..d83d3a6c5cf 100644
--- a/src/libsyntax_pos/lib.rs
+++ b/src/libsyntax_pos/lib.rs
@@ -481,6 +481,9 @@ pub fn is_imported(&self) -> bool {
         self.src.is_none()
     }
 
+    pub fn byte_length(&self) -> u32 {
+        self.end_pos.0 - self.start_pos.0
+    }
     pub fn count_lines(&self) -> usize {
         self.lines.borrow().len()
     }