Auto merge of #38482 - est31:i128, r=eddyb

i128 and u128 support

Brings i128 and u128 support to nightly rust, behind a feature flag. The goal of this PR is to do the bulk of the work for 128 bit integer support. Smaller but just as tricky features needed for stabilisation like 128 bit enum discriminants are left for future PRs.

Rebased version of  #37900, which in turn was a rebase + improvement of #35954 . Sadly I couldn't reopen #37900 due to github. There goes my premium position in the homu queue...

[plugin-breaking-change]

cc #35118 (tracking issue)

2 files changed, 9 insertions, 3 deletions

diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs
index 24178e1f675..32b61a88ac1 100644
--- a/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@ -28,6 +28,8 @@ use std::path::{Path, PathBuf};
 use std::rc::Rc;
 use std::str;
 
+use rustc_i128::u128;
+
 pub type PResult<'a, T> = Result<T, DiagnosticBuilder<'a>>;
 
 #[macro_use]
@@ -557,18 +559,20 @@ pub fn integer_lit(s: &str, suffix: Option<Symbol>, sd: &Handler, sp: Span) -> a
             "i16" => ast::LitIntType::Signed(ast::IntTy::I16),
             "i32" => ast::LitIntType::Signed(ast::IntTy::I32),
             "i64" => ast::LitIntType::Signed(ast::IntTy::I64),
+            "i128" => ast::LitIntType::Signed(ast::IntTy::I128),
             "usize" => ast::LitIntType::Unsigned(ast::UintTy::Us),
             "u8"  => ast::LitIntType::Unsigned(ast::UintTy::U8),
             "u16" => ast::LitIntType::Unsigned(ast::UintTy::U16),
             "u32" => ast::LitIntType::Unsigned(ast::UintTy::U32),
             "u64" => ast::LitIntType::Unsigned(ast::UintTy::U64),
+            "u128" => ast::LitIntType::Unsigned(ast::UintTy::U128),
             suf => {
                 // i<digits> and u<digits> look like widths, so lets
                 // give an error message along those lines
                 if looks_like_width_suffix(&['i', 'u'], suf) {
                     sd.struct_span_err(sp, &format!("invalid width `{}` for integer literal",
                                              &suf[1..]))
-                      .help("valid widths are 8, 16, 32 and 64")
+                      .help("valid widths are 8, 16, 32, 64 and 128")
                       .emit();
                 } else {
                     sd.struct_span_err(sp, &format!("invalid suffix `{}` for numeric literal", suf))
@@ -585,7 +589,7 @@ pub fn integer_lit(s: &str, suffix: Option<Symbol>, sd: &Handler, sp: Span) -> a
     debug!("integer_lit: the type is {:?}, base {:?}, the new string is {:?}, the original \
            string was {:?}, the original suffix was {:?}", ty, base, s, orig, suffix);
 
-    match u64::from_str_radix(s, base) {
+    match u128::from_str_radix(s, base) {
         Ok(r) => ast::LitKind::Int(r, ty),
         Err(_) => {
             // small bases are lexed as if they were base 10, e.g, the string
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index a0ed50b33a4..2bb38433a26 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -64,6 +64,8 @@ use std::path::{Path, PathBuf};
 use std::rc::Rc;
 use std::slice;
 
+use rustc_i128::u128;
+
 bitflags! {
     flags Restrictions: u8 {
         const RESTRICTION_STMT_EXPR         = 1 << 0,
@@ -2044,7 +2046,7 @@ impl<'a> Parser<'a> {
     pub fn mk_lit_u32(&mut self, i: u32, attrs: ThinVec<Attribute>) -> P<Expr> {
         let span = &self.span;
         let lv_lit = P(codemap::Spanned {
-            node: LitKind::Int(i as u64, ast::LitIntType::Unsigned(UintTy::U32)),
+            node: LitKind::Int(i as u128, ast::LitIntType::Unsigned(UintTy::U32)),
             span: *span
         });