diff --git a/codegen/build.rs b/codegen/build.rs
index cd097465..de393f85 100644
--- a/codegen/build.rs
+++ b/codegen/build.rs
@@ -8,8 +8,8 @@ use yansi::Color::{Red, Yellow, Blue, White};
 use version_check::{supports_features, is_min_version, is_min_date};
 
 // Specifies the minimum nightly version needed to compile Rocket's codegen.
-const MIN_DATE: &'static str = "2017-08-10";
-const MIN_VERSION: &'static str = "1.21.0-nightly";
+const MIN_DATE: &'static str = "2017-09-25";
+const MIN_VERSION: &'static str = "1.22.0-nightly";
 
 fn main() {
     let ok_channel = supports_features();
diff --git a/codegen/src/lib.rs b/codegen/src/lib.rs
index d4d0a247..a638dbd3 100644
--- a/codegen/src/lib.rs
+++ b/codegen/src/lib.rs
@@ -144,10 +144,8 @@
 #![allow(deprecated)]
 
 #[macro_use] extern crate log;
-extern crate rustc;
 extern crate syntax;
 extern crate syntax_ext;
-extern crate syntax_pos;
 extern crate rustc_plugin;
 extern crate rocket;
 
diff --git a/codegen/src/parser/param.rs b/codegen/src/parser/param.rs
index 4d0d3449..059d8128 100644
--- a/codegen/src/parser/param.rs
+++ b/codegen/src/parser/param.rs
@@ -1,8 +1,8 @@
 use syntax::ast::Ident;
 use syntax::ext::base::ExtCtxt;
-use syntax::codemap::{Span, Spanned, BytePos};
+use syntax::codemap::{Span, Spanned};
 
-use utils::span;
+use utils::{span, SpanExt};
 
 #[derive(Debug)]
 pub enum Param {
@@ -67,13 +67,11 @@ impl<'s, 'a, 'c> Iterator for ParamIter<'s, 'a, 'c> {
             (false, full_param)
         };
 
-        let mut param_span = self.span;
-        param_span.lo = self.span.lo + BytePos(start as u32);
-        param_span.hi = self.span.lo + BytePos((end + 1) as u32);
+        let param_span = self.span.trim_left(start).shorten_to(end + 1);
 
         // Advance the string and span.
         self.string = &self.string[(end + 1)..];
-        self.span.lo = self.span.lo + BytePos((end + 1) as u32);
+        self.span = self.span.trim_left(end + 1);
 
         let spanned_ident = span(Ident::from_str(param), param_span);
         if is_many {
diff --git a/codegen/src/utils/span_ext.rs b/codegen/src/utils/span_ext.rs
index 932e69ba..41f17ce4 100644
--- a/codegen/src/utils/span_ext.rs
+++ b/codegen/src/utils/span_ext.rs
@@ -18,29 +18,24 @@ pub trait SpanExt {
 }
 
 impl SpanExt for Span {
-    fn trim_left(mut self, length: usize) -> Span {
-        self.lo = self.lo + BytePos(length as u32);
-        self
+    fn trim_left(self, length: usize) -> Span {
+        self.with_lo(self.lo() + BytePos(length as u32))
     }
 
-    fn trim_right(mut self, length: usize) -> Span {
-        self.hi = self.hi - BytePos(length as u32);
-        self
+    fn trim_right(self, length: usize) -> Span {
+        self.with_hi(self.hi() - BytePos(length as u32))
     }
 
-    fn shorten_to(mut self, to_length: usize) -> Span {
-        self.hi = self.lo + BytePos(to_length as u32);
-        self
+    fn shorten_to(self, to_length: usize) -> Span {
+        self.with_hi(self.lo() + BytePos(to_length as u32))
     }
 
-    fn shorten_upto(mut self, length: usize) -> Span {
-        self.lo = self.hi - BytePos(length as u32);
-        self
+    fn shorten_upto(self, length: usize) -> Span {
+        self.with_lo(self.hi() - BytePos(length as u32))
     }
 
-    fn trim(mut self, length: u32) -> Span {
-        self.lo = self.lo + BytePos(length);
-        self.hi = self.hi - BytePos(length);
-        self
+    fn trim(self, length: u32) -> Span {
+        self.with_lo(self.lo() + BytePos(length))
+            .with_hi(self.hi() - BytePos(length))
     }
 }