1 files changed, 17 insertions, 10 deletions
diff --git a/compiler/rustc_lexer/src/lib.rs b/compiler/rustc_lexer/src/lib.rs
index 51515976e..3fbabbc63 100644
--- a/compiler/rustc_lexer/src/lib.rs
+++ b/compiler/rustc_lexer/src/lib.rs
@@ -88,7 +88,9 @@ pub enum TokenKind {
     /// tokens.
     UnknownPrefix,
 
-    /// Examples: `"12_u8"`, `"1.0e-40"`, `b"123`.
+    /// Examples: `12u8`, `1.0e-40`, `b"123"`. Note that `_` is an invalid
+    /// suffix, but may be present here on string and float literals. Users of
+    /// this type will need to check for and reject that case.
     ///
     /// See [LiteralKind] for more details.
     Literal { kind: LiteralKind, suffix_start: u32 },
@@ -165,11 +167,15 @@ pub enum DocStyle {
     Inner,
 }
 
+// Note that the suffix is *not* considered when deciding the `LiteralKind` in
+// this type. This means that float literals like `1f32` are classified by this
+// type as `Int`. (Compare against `rustc_ast::token::LitKind` and
+// `rustc_ast::ast::LitKind.)
 #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
 pub enum LiteralKind {
-    /// "12_u8", "0o100", "0b120i99"
+    /// "12_u8", "0o100", "0b120i99", "1f32".
     Int { base: Base, empty_int: bool },
-    /// "12.34f32", "0b100.100"
+    /// "12.34f32", "1e3", but not "1f32`.
     Float { base: Base, empty_exponent: bool },
     /// "'a'", "'\\'", "'''", "';"
     Char { terminated: bool },
@@ -203,13 +209,13 @@ pub enum RawStrError {
 #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
 pub enum Base {
     /// Literal starts with "0b".
-    Binary,
+    Binary = 2,
     /// Literal starts with "0o".
-    Octal,
-    /// Literal starts with "0x".
-    Hexadecimal,
+    Octal = 8,
     /// Literal doesn't contain a prefix.
-    Decimal,
+    Decimal = 10,
+    /// Literal starts with "0x".
+    Hexadecimal = 16,
 }
 
 /// `rustc` allows files to have a shebang, e.g. "#!/usr/bin/rustrun",
@@ -840,12 +846,13 @@ impl Cursor<'_> {
         self.eat_decimal_digits()
     }
 
-    // Eats the suffix of the literal, e.g. "_u8".
+    // Eats the suffix of the literal, e.g. "u8".
     fn eat_literal_suffix(&mut self) {
         self.eat_identifier();
     }
 
-    // Eats the identifier.
+    // Eats the identifier. Note: succeeds on `_`, which isn't a valid
+    // identifer.
     fn eat_identifier(&mut self) {
         if !is_id_start(self.first()) {
             return;