Allow lexer to recover from some homoglyphs

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

@@ -1,5 +1,6 @@
 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() {}

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

@@ -14,5 +14,14 @@ 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: aborting due to 2 previous errors
+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 `std::ops::Sub<{integer}>` is not implemented for `{float}`
 
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0277`.

src/test/ui/parser/recover-from-homoglyph.rs

@@ -0,0 +1,4 @@
+fn main() {
+    println!(""); //~ ERROR unknown start of token: \u{37e}
+    let x: usize = (); //~ ERROR mismatched types
+}

src/test/ui/parser/recover-from-homoglyph.stderr

@@ -0,0 +1,22 @@
+error: unknown start of token: \u{37e}
+  --> $DIR/recover-from-homoglyph.rs:2:17
+   |
+LL |     println!("");
+   |                 ^
+help: Unicode character ';' (Greek Question Mark) looks like ';' (Semicolon), but it is not
+   |
+LL |     println!("");
+   |                 ^
+
+error[E0308]: mismatched types
+  --> $DIR/recover-from-homoglyph.rs:3:20
+   |
+LL |     let x: usize = ();
+   |                    ^^ expected usize, found ()
+   |
+   = note: expected type `usize`
+              found type `()`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0308`.