diff --git a/src/Cargo.lock b/src/Cargo.lock
index 8bf4b6ad3e0..3508e8c070b 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 0935ec1b01c..442b92be1cb 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 760aaa8a957..dd8129bab51 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 caea1497181..75ce8b675f3 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
 //