From dd8f7cd126403955295c8b0cdbccc5ca5cbef763 Mon Sep 17 00:00:00 2001
From: Inokentiy Babushkin <twk@twki.de>
Date: Sat, 10 Jun 2017 16:09:51 +0200
Subject: [PATCH] Moved FileMap construction to it's own constructor.

The rationale is that BOM stripping is needed for lazy source loading
for external crates, and duplication can be avoided by moving the
corresponding functionality to libsyntax_pos.
---
 src/Cargo.lock               |  1 +
 src/libsyntax/codemap.rs     | 30 +++--------------------------
 src/libsyntax_pos/Cargo.toml |  1 +
 src/libsyntax_pos/lib.rs     | 37 ++++++++++++++++++++++++++++++++++++
 4 files changed, 42 insertions(+), 27 deletions(-)

diff --git a/src/Cargo.lock b/src/Cargo.lock
index 8bf4b6ad3e0c..3508e8c070bb 100644
--- a/src/Cargo.lock
+++ b/src/Cargo.lock
@@ -1682,6 +1682,7 @@ dependencies = [
 name = "syntax_pos"
 version = "0.0.0"
 dependencies = [
+ "rustc_data_structures 0.0.0",
  "serialize 0.0.0",
 ]
 
diff --git a/src/libsyntax/codemap.rs b/src/libsyntax/codemap.rs
index 0935ec1b01c9..442b92be1cb8 100644
--- a/src/libsyntax/codemap.rs
+++ b/src/libsyntax/codemap.rs
@@ -27,12 +27,9 @@ use std::rc::Rc;
 
 use std::env;
 use std::fs;
-use std::hash::Hasher;
 use std::io::{self, Read};
 use errors::CodeMapper;
 
-use rustc_data_structures::stable_hasher::StableHasher;
-
 /// Return the span itself if it doesn't come from a macro expansion,
 /// otherwise return the call site span up to the `enclosing_sp` by
 /// following the `expn_info` chain.
@@ -161,34 +158,13 @@ impl CodeMap {
 
     /// Creates a new filemap without setting its line information. If you don't
     /// intend to set the line information yourself, you should use new_filemap_and_lines.
-    pub fn new_filemap(&self, filename: FileName, mut src: String) -> Rc<FileMap> {
+    pub fn new_filemap(&self, filename: FileName, src: String) -> Rc<FileMap> {
         let start_pos = self.next_start_pos();
         let mut files = self.files.borrow_mut();
 
-        // Remove utf-8 BOM if any.
-        if src.starts_with("\u{feff}") {
-            src.drain(..3);
-        }
-
-        let end_pos = start_pos + src.len();
-
         let (filename, was_remapped) = self.path_mapping.map_prefix(filename);
-
-        let mut hasher: StableHasher<u128> = StableHasher::new();
-        hasher.write(src.as_bytes());
-        let src_hash = hasher.finish();
-
-        let filemap = Rc::new(FileMap {
-            name: filename,
-            name_was_remapped: was_remapped,
-            crate_of_origin: 0,
-            src: Some(Rc::new(src)),
-            src_hash: src_hash,
-            start_pos: Pos::from_usize(start_pos),
-            end_pos: Pos::from_usize(end_pos),
-            lines: RefCell::new(Vec::new()),
-            multibyte_chars: RefCell::new(Vec::new()),
-        });
+        let filemap =
+            Rc::new(FileMap::new(filename, was_remapped, src, Pos::from_usize(start_pos)));
 
         files.push(filemap.clone());
 
diff --git a/src/libsyntax_pos/Cargo.toml b/src/libsyntax_pos/Cargo.toml
index 760aaa8a9578..dd8129bab510 100644
--- a/src/libsyntax_pos/Cargo.toml
+++ b/src/libsyntax_pos/Cargo.toml
@@ -10,3 +10,4 @@ crate-type = ["dylib"]
 
 [dependencies]
 serialize = { path = "../libserialize" }
+rustc_data_structures = { path = "../librustc_data_structures" }
diff --git a/src/libsyntax_pos/lib.rs b/src/libsyntax_pos/lib.rs
index caea14971816..75ce8b675f3d 100644
--- a/src/libsyntax_pos/lib.rs
+++ b/src/libsyntax_pos/lib.rs
@@ -38,6 +38,11 @@ use std::ops::{Add, Sub};
 use std::rc::Rc;
 use std::cmp;
 use std::fmt;
+use std::hash::Hasher;
+
+use rustc_data_structures::stable_hasher::StableHasher;
+
+extern crate rustc_data_structures;
 
 use serialize::{Encodable, Decodable, Encoder, Decoder};
 
@@ -522,6 +527,31 @@ impl fmt::Debug for FileMap {
 }
 
 impl FileMap {
+    pub fn new(name: FileName,
+               name_was_remapped: bool,
+               mut src: String,
+               start_pos: BytePos) -> FileMap {
+        remove_bom(&mut src);
+
+        let mut hasher: StableHasher<u128> = StableHasher::new();
+        hasher.write(src.as_bytes());
+        let src_hash = hasher.finish();
+
+        let end_pos = start_pos.to_usize() + src.len();
+
+        FileMap {
+            name: name,
+            name_was_remapped: name_was_remapped,
+            crate_of_origin: 0,
+            src: Some(Rc::new(src)),
+            src_hash: src_hash,
+            start_pos: start_pos,
+            end_pos: Pos::from_usize(end_pos),
+            lines: RefCell::new(Vec::new()),
+            multibyte_chars: RefCell::new(Vec::new()),
+        }
+    }
+
     /// EFFECT: register a start-of-line offset in the
     /// table of line-beginnings.
     /// UNCHECKED INVARIANT: these offsets must be added in the right
@@ -621,6 +651,13 @@ impl FileMap {
     }
 }
 
+/// Remove utf-8 BOM if any.
+fn remove_bom(src: &mut String) {
+    if src.starts_with("\u{feff}") {
+        src.drain(..3);
+    }
+}
+
 // _____________________________________________________________________________
 // Pos, BytePos, CharPos
 //