diff --git a/src/libsyntax_pos/Cargo.toml b/src/libsyntax_pos/Cargo.toml
index 08ee2e0f3762..5658451c54f7 100644
--- a/src/libsyntax_pos/Cargo.toml
+++ b/src/libsyntax_pos/Cargo.toml
@@ -2,6 +2,7 @@
 authors = ["The Rust Project Developers"]
 name = "syntax_pos"
 version = "0.0.0"
+edition = "2018"
 
 [lib]
 name = "syntax_pos"
diff --git a/src/libsyntax_pos/analyze_source_file.rs b/src/libsyntax_pos/analyze_source_file.rs
index 3abd260ac6f8..18387bd5a091 100644
--- a/src/libsyntax_pos/analyze_source_file.rs
+++ b/src/libsyntax_pos/analyze_source_file.rs
@@ -36,7 +36,7 @@ pub fn analyze_source_file(
     (lines, multi_byte_chars, non_narrow_chars)
 }
 
-cfg_if! {
+cfg_if::cfg_if! {
     if #[cfg(all(any(target_arch = "x86", target_arch = "x86_64")))] {
         fn analyze_source_file_dispatch(src: &str,
                                     source_file_start_pos: BytePos,
diff --git a/src/libsyntax_pos/edition.rs b/src/libsyntax_pos/edition.rs
index f5a745a9cd50..a0b0052f26da 100644
--- a/src/libsyntax_pos/edition.rs
+++ b/src/libsyntax_pos/edition.rs
@@ -27,7 +27,7 @@ pub const EDITION_NAME_LIST: &str = "2015|2018";
 pub const DEFAULT_EDITION: Edition = Edition::Edition2015;
 
 impl fmt::Display for Edition {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let s = match *self {
             Edition::Edition2015 => "2015",
             Edition::Edition2018 => "2018",
diff --git a/src/libsyntax_pos/hygiene.rs b/src/libsyntax_pos/hygiene.rs
index 6e32a05dee36..0c645fc678ca 100644
--- a/src/libsyntax_pos/hygiene.rs
+++ b/src/libsyntax_pos/hygiene.rs
@@ -5,10 +5,10 @@
 //! and definition contexts*. J. Funct. Program. 22, 2 (March 2012), 181-216.
 //! DOI=10.1017/S0956796812000093 <https://doi.org/10.1017/S0956796812000093>
 
-use GLOBALS;
-use Span;
-use edition::{Edition, DEFAULT_EDITION};
-use symbol::{keywords, Symbol};
+use crate::GLOBALS;
+use crate::Span;
+use crate::edition::{Edition, DEFAULT_EDITION};
+use crate::symbol::{keywords, Symbol};
 
 use serialize::{Encodable, Decodable, Encoder, Decoder};
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
@@ -525,7 +525,7 @@ impl SyntaxContext {
 }
 
 impl fmt::Debug for SyntaxContext {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "#{}", self.0)
     }
 }
diff --git a/src/libsyntax_pos/lib.rs b/src/libsyntax_pos/lib.rs
index 2a8577923968..13e7307570a4 100644
--- a/src/libsyntax_pos/lib.rs
+++ b/src/libsyntax_pos/lib.rs
@@ -8,10 +8,11 @@
       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
       html_root_url = "https://doc.rust-lang.org/nightly/")]
 
+#![deny(rust_2018_idioms)]
+
 #![feature(const_fn)]
 #![feature(crate_visibility_modifier)]
 #![feature(custom_attribute)]
-#![feature(nll)]
 #![feature(non_exhaustive)]
 #![feature(optin_builtin_traits)]
 #![feature(rustc_attrs)]
@@ -19,23 +20,11 @@
 #![feature(step_trait)]
 #![cfg_attr(not(stage0), feature(stdsimd))]
 
-extern crate arena;
-#[macro_use]
-extern crate rustc_data_structures;
-
-#[macro_use]
-extern crate scoped_tls;
-
 use serialize::{Encodable, Decodable, Encoder, Decoder};
 
-extern crate serialize;
+#[allow(unused_extern_crates)]
 extern crate serialize as rustc_serialize; // used by deriving
 
-#[macro_use]
-extern crate cfg_if;
-
-extern crate unicode_width;
-
 pub mod edition;
 pub mod hygiene;
 pub use hygiene::{Mark, SyntaxContext, ExpnInfo, ExpnFormat, CompilerDesugaringKind};
@@ -74,7 +63,7 @@ impl Globals {
     }
 }
 
-scoped_thread_local!(pub static GLOBALS: Globals);
+scoped_tls::scoped_thread_local!(pub static GLOBALS: Globals);
 
 /// Differentiates between real files and common virtual files.
 #[derive(Debug, Eq, PartialEq, Clone, Ord, PartialOrd, Hash, RustcDecodable, RustcEncodable)]
@@ -100,8 +89,8 @@ pub enum FileName {
 }
 
 impl std::fmt::Display for FileName {
-    fn fmt(&self, fmt: &mut std::fmt::Formatter) -> std::fmt::Result {
-        use self::FileName::*;
+    fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        use FileName::*;
         match *self {
             Real(ref path) => write!(fmt, "{}", path.display()),
             Macros(ref name) => write!(fmt, "<{} macros>", name),
@@ -127,7 +116,7 @@ impl From<PathBuf> for FileName {
 
 impl FileName {
     pub fn is_real(&self) -> bool {
-        use self::FileName::*;
+        use FileName::*;
         match *self {
             Real(_) => true,
             Macros(_) |
@@ -143,7 +132,7 @@ impl FileName {
     }
 
     pub fn is_macros(&self) -> bool {
-        use self::FileName::*;
+        use FileName::*;
         match *self {
             Real(_) |
             Anon(_) |
@@ -611,7 +600,7 @@ impl serialize::UseSpecializedDecodable for Span {
     }
 }
 
-pub fn default_span_debug(span: Span, f: &mut fmt::Formatter) -> fmt::Result {
+pub fn default_span_debug(span: Span, f: &mut fmt::Formatter<'_>) -> fmt::Result {
     f.debug_struct("Span")
         .field("lo", &span.lo())
         .field("hi", &span.hi())
@@ -620,13 +609,13 @@ pub fn default_span_debug(span: Span, f: &mut fmt::Formatter) -> fmt::Result {
 }
 
 impl fmt::Debug for Span {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         SPAN_DEBUG.with(|span_debug| span_debug.get()(*self, f))
     }
 }
 
 impl fmt::Debug for SpanData {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         SPAN_DEBUG.with(|span_debug| span_debug.get()(Span::new(self.lo, self.hi, self.ctxt), f))
     }
 }
@@ -1009,7 +998,7 @@ impl Decodable for SourceFile {
                 // `crate_of_origin` has to be set by the importer.
                 // This value matches up with rustc::hir::def_id::INVALID_CRATE.
                 // That constant is not available here unfortunately :(
-                crate_of_origin: ::std::u32::MAX - 1,
+                crate_of_origin: std::u32::MAX - 1,
                 start_pos,
                 end_pos,
                 src: None,
@@ -1025,7 +1014,7 @@ impl Decodable for SourceFile {
 }
 
 impl fmt::Debug for SourceFile {
-    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(fmt, "SourceFile({})", self.name)
     }
 }
@@ -1111,7 +1100,7 @@ impl SourceFile {
 
     /// Get a line from the list of pre-computed line-beginnings.
     /// The line number here is 0-based.
-    pub fn get_line(&self, line_number: usize) -> Option<Cow<str>> {
+    pub fn get_line(&self, line_number: usize) -> Option<Cow<'_, str>> {
         fn get_until_newline(src: &str, begin: usize) -> &str {
             // We can't use `lines.get(line_number+1)` because we might
             // be parsing when we call this function and thus the current
@@ -1353,7 +1342,7 @@ pub struct FileLines {
     pub lines: Vec<LineInfo>
 }
 
-thread_local!(pub static SPAN_DEBUG: Cell<fn(Span, &mut fmt::Formatter) -> fmt::Result> =
+thread_local!(pub static SPAN_DEBUG: Cell<fn(Span, &mut fmt::Formatter<'_>) -> fmt::Result> =
                 Cell::new(default_span_debug));
 
 #[derive(Debug)]
diff --git a/src/libsyntax_pos/span_encoding.rs b/src/libsyntax_pos/span_encoding.rs
index 8cb3bc2144da..03d7a9eb7423 100644
--- a/src/libsyntax_pos/span_encoding.rs
+++ b/src/libsyntax_pos/span_encoding.rs
@@ -4,9 +4,9 @@
 // The encoding format for inline spans were obtained by optimizing over crates in rustc/libstd.
 // See https://internals.rust-lang.org/t/rfc-compiler-refactoring-spans/1357/28
 
-use GLOBALS;
-use {BytePos, SpanData};
-use hygiene::SyntaxContext;
+use crate::GLOBALS;
+use crate::{BytePos, SpanData};
+use crate::hygiene::SyntaxContext;
 
 use rustc_data_structures::fx::FxHashMap;
 use std::hash::{Hash, Hasher};
diff --git a/src/libsyntax_pos/symbol.rs b/src/libsyntax_pos/symbol.rs
index 7097f332b8b8..0eecdbfa9763 100644
--- a/src/libsyntax_pos/symbol.rs
+++ b/src/libsyntax_pos/symbol.rs
@@ -5,6 +5,7 @@
 use arena::DroplessArena;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::indexed_vec::Idx;
+use rustc_data_structures::newtype_index;
 use serialize::{Decodable, Decoder, Encodable, Encoder};
 
 use std::fmt;
@@ -12,8 +13,8 @@ use std::str;
 use std::cmp::{PartialEq, Ordering, PartialOrd, Ord};
 use std::hash::{Hash, Hasher};
 
-use hygiene::SyntaxContext;
-use {Span, DUMMY_SP, GLOBALS};
+use crate::hygiene::SyntaxContext;
+use crate::{Span, DUMMY_SP, GLOBALS};
 
 #[derive(Copy, Clone, Eq)]
 pub struct Ident {
@@ -100,13 +101,13 @@ impl Hash for Ident {
 }
 
 impl fmt::Debug for Ident {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "{}{:?}", self.name, self.span.ctxt())
     }
 }
 
 impl fmt::Display for Ident {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmt::Display::fmt(&self.name, f)
     }
 }
@@ -181,7 +182,7 @@ impl Symbol {
     pub fn as_str(self) -> LocalInternedString {
         with_interner(|interner| unsafe {
             LocalInternedString {
-                string: ::std::mem::transmute::<&str, &str>(interner.get(self))
+                string: std::mem::transmute::<&str, &str>(interner.get(self))
             }
         })
     }
@@ -198,7 +199,7 @@ impl Symbol {
 }
 
 impl fmt::Debug for Symbol {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let is_gensymed = with_interner(|interner| interner.is_gensymed(*self));
         if is_gensymed {
             write!(f, "{}({:?})", self, self.0)
@@ -209,7 +210,7 @@ impl fmt::Debug for Symbol {
 }
 
 impl fmt::Display for Symbol {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmt::Display::fmt(&self.as_str(), f)
     }
 }
@@ -226,7 +227,7 @@ impl Decodable for Symbol {
     }
 }
 
-impl<T: ::std::ops::Deref<Target=str>> PartialEq<T> for Symbol {
+impl<T: std::ops::Deref<Target=str>> PartialEq<T> for Symbol {
     fn eq(&self, other: &T) -> bool {
         self.as_str() == other.deref()
     }
@@ -335,7 +336,7 @@ macro_rules! declare_keywords {(
             };
         )*
 
-        impl ::std::str::FromStr for Keyword {
+        impl std::str::FromStr for Keyword {
             type Err = ();
 
             fn from_str(s: &str) -> Result<Self, ()> {
@@ -519,40 +520,40 @@ impl LocalInternedString {
     }
 }
 
-impl<U: ?Sized> ::std::convert::AsRef<U> for LocalInternedString
+impl<U: ?Sized> std::convert::AsRef<U> for LocalInternedString
 where
-    str: ::std::convert::AsRef<U>
+    str: std::convert::AsRef<U>
 {
     fn as_ref(&self) -> &U {
         self.string.as_ref()
     }
 }
 
-impl<T: ::std::ops::Deref<Target = str>> ::std::cmp::PartialEq<T> for LocalInternedString {
+impl<T: std::ops::Deref<Target = str>> std::cmp::PartialEq<T> for LocalInternedString {
     fn eq(&self, other: &T) -> bool {
         self.string == other.deref()
     }
 }
 
-impl ::std::cmp::PartialEq<LocalInternedString> for str {
+impl std::cmp::PartialEq<LocalInternedString> for str {
     fn eq(&self, other: &LocalInternedString) -> bool {
         self == other.string
     }
 }
 
-impl<'a> ::std::cmp::PartialEq<LocalInternedString> for &'a str {
+impl<'a> std::cmp::PartialEq<LocalInternedString> for &'a str {
     fn eq(&self, other: &LocalInternedString) -> bool {
         *self == other.string
     }
 }
 
-impl ::std::cmp::PartialEq<LocalInternedString> for String {
+impl std::cmp::PartialEq<LocalInternedString> for String {
     fn eq(&self, other: &LocalInternedString) -> bool {
         self == other.string
     }
 }
 
-impl<'a> ::std::cmp::PartialEq<LocalInternedString> for &'a String {
+impl<'a> std::cmp::PartialEq<LocalInternedString> for &'a String {
     fn eq(&self, other: &LocalInternedString) -> bool {
         *self == other.string
     }
@@ -561,19 +562,19 @@ impl<'a> ::std::cmp::PartialEq<LocalInternedString> for &'a String {
 impl !Send for LocalInternedString {}
 impl !Sync for LocalInternedString {}
 
-impl ::std::ops::Deref for LocalInternedString {
+impl std::ops::Deref for LocalInternedString {
     type Target = str;
     fn deref(&self) -> &str { self.string }
 }
 
 impl fmt::Debug for LocalInternedString {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmt::Debug::fmt(self.string, f)
     }
 }
 
 impl fmt::Display for LocalInternedString {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmt::Display::fmt(self.string, f)
     }
 }
@@ -640,7 +641,7 @@ impl Ord for InternedString {
     }
 }
 
-impl<T: ::std::ops::Deref<Target = str>> PartialEq<T> for InternedString {
+impl<T: std::ops::Deref<Target = str>> PartialEq<T> for InternedString {
     fn eq(&self, other: &T) -> bool {
         self.with(|string| string == other.deref())
     }
@@ -676,20 +677,20 @@ impl<'a> PartialEq<InternedString> for &'a String {
     }
 }
 
-impl ::std::convert::From<InternedString> for String {
+impl std::convert::From<InternedString> for String {
     fn from(val: InternedString) -> String {
         val.as_symbol().to_string()
     }
 }
 
 impl fmt::Debug for InternedString {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         self.with(|str| fmt::Debug::fmt(&str, f))
     }
 }
 
 impl fmt::Display for InternedString {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         self.with(|str| fmt::Display::fmt(&str, f))
     }
 }
@@ -709,7 +710,7 @@ impl Encodable for InternedString {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use Globals;
+    use crate::Globals;
 
     #[test]
     fn interner_tests() {