2 files changed, 12 insertions, 5 deletions
diff --git a/src/libsyntax/parse/lexer/mod.rs b/src/libsyntax/parse/lexer/mod.rs
index a9dd234e1ad..50a398d8c63 100644
--- a/src/libsyntax/parse/lexer/mod.rs
+++ b/src/libsyntax/parse/lexer/mod.rs
@@ -1075,9 +1075,16 @@ impl<'a> StringReader<'a> {
                 self.bump();
             }
             if self.scan_digits(10, 10) == 0 {
-                self.err_span_(self.pos,
-                               self.next_pos,
-                               "expected at least one digit in exponent")
+                let mut err = self.struct_span_fatal(
+                    self.pos, self.next_pos,
+                    "expected at least one digit in exponent"
+                );
+                if let Some(ch) = self.ch {
+                    // check for e.g. Unicode minus '−' (Issue #49746)
+                    unicode_chars::check_for_substitution(self, ch, &mut err);
+                }
+                err.emit();
+                FatalError.raise();
             }
         }
     }
diff --git a/src/libsyntax/parse/lexer/unicode_chars.rs b/src/libsyntax/parse/lexer/unicode_chars.rs
index 35afe8dd56d..3c0bb82212f 100644
--- a/src/libsyntax/parse/lexer/unicode_chars.rs
+++ b/src/libsyntax/parse/lexer/unicode_chars.rs
@@ -344,9 +344,9 @@ pub fn check_for_substitution<'a>(reader: &StringReader<'a>,
         match ASCII_ARRAY.iter().find(|&&(c, _)| c == ascii_char) {
             Some(&(ascii_char, ascii_name)) => {
                 let msg =
-                    format!("unicode character '{}' ({}) looks like '{}' ({}), but it's not",
+                    format!("Unicode character '{}' ({}) looks like '{}' ({}), but it is not",
                             ch, u_name, ascii_char, ascii_name);
-                err.span_help(span, &msg);
+                err.span_suggestion(span, &msg, ascii_char.to_string());
             },
             None => {
                 let msg = format!("substitution character not found for '{}'", ch);