Use LitKind::Err for floats with empty exponents.

This prevents a follow-up type error in a test, which seems fine.

Author: nnethercote

compiler/rustc_parse/src/lexer/mod.rs

@@ -501,9 +501,11 @@ impl<'sess, 'src> StringReader<'sess, 'src> {
                 (kind, self.symbol_from_to(start, end))
             }
             rustc_lexer::LiteralKind::Float { base, empty_exponent } => {
+                let mut kind = token::Float;
                 if empty_exponent {
                     let span = self.mk_sp(start, self.pos);
-                    self.dcx().emit_err(errors::EmptyExponentFloat { span });
+                    let guar = self.dcx().emit_err(errors::EmptyExponentFloat { span });
+                    kind = token::Err(guar);
                 }
                 let base = match base {
                     Base::Hexadecimal => Some("hexadecimal"),
@@ -515,7 +517,7 @@ impl<'sess, 'src> StringReader<'sess, 'src> {
                     let span = self.mk_sp(start, end);
                     self.dcx().emit_err(errors::FloatLiteralUnsupportedBase { span, base });
                 }
-                (token::Float, self.symbol_from_to(start, end))
+                (kind, self.symbol_from_to(start, end))
             }
         }
     }

tests/ui/did_you_mean/issue-49746-unicode-confusable-in-float-literal-expt.rs

@@ -1,6 +1,5 @@
 const UNIVERSAL_GRAVITATIONAL_CONSTANT: f64 = 6.674e−11; // m³⋅kg⁻¹⋅s⁻²
 //~^ ERROR expected at least one digit in exponent
 //~| ERROR unknown start of token: \u{2212}
-//~| ERROR cannot subtract `{integer}` from `{float}`
 
 fn main() {}

tests/ui/did_you_mean/issue-49746-unicode-confusable-in-float-literal-expt.stderr

@@ -15,24 +15,5 @@ help: Unicode character '−' (Minus Sign) looks like '-' (Minus/Hyphen), but it
 LL | const UNIVERSAL_GRAVITATIONAL_CONSTANT: f64 = 6.674e-11; // m³⋅kg⁻¹⋅s⁻²
    |                                                     ~
 
-error[E0277]: cannot subtract `{integer}` from `{float}`
-  --> $DIR/issue-49746-unicode-confusable-in-float-literal-expt.rs:1:53
-   |
-LL | const UNIVERSAL_GRAVITATIONAL_CONSTANT: f64 = 6.674e−11; // m³⋅kg⁻¹⋅s⁻²
-   |                                                     ^ no implementation for `{float} - {integer}`
-   |
-   = help: the trait `Sub<{integer}>` is not implemented for `{float}`
-   = help: the following other types implement trait `Sub<Rhs>`:
-             <isize as Sub>
-             <isize as Sub<&isize>>
-             <i8 as Sub>
-             <i8 as Sub<&i8>>
-             <i16 as Sub>
-             <i16 as Sub<&i16>>
-             <i32 as Sub>
-             <i32 as Sub<&i32>>
-           and 48 others
-
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0277`.