Require at least one digit after decimal point

Author: dtolnay

src/de.rs

@@ -451,30 +451,33 @@ impl<'de, R: Read<'de>> Deserializer<R> {
         &mut self,
         positive: bool,
         mut significand: u64,
-        mut exponent: i32,
+        exponent_before_decimal_point: i32,
     ) -> Result<f64> {
         self.eat_char();
 
+        let mut exponent_after_decimal_point = 0;
         while let c @ b'0'..=b'9' = tri!(self.peek_or_null()) {
             let digit = (c - b'0') as u64;
 
             if overflow!(significand * 10 + digit, u64::max_value()) {
+                let exponent = exponent_before_decimal_point + exponent_after_decimal_point;
                 return self.parse_decimal_overflow(positive, significand, exponent);
             }
 
             self.eat_char();
             significand = significand * 10 + digit;
-            exponent -= 1;
+            exponent_after_decimal_point -= 1;
         }
 
         // Error if there is not at least one digit after the decimal point.
-        if exponent == 0 {
+        if exponent_after_decimal_point == 0 {
             match tri!(self.peek()) {
                 Some(_) => return Err(self.peek_error(ErrorCode::InvalidNumber)),
                 None => return Err(self.peek_error(ErrorCode::EofWhileParsingValue)),
             }
         }
 
+        let exponent = exponent_before_decimal_point + exponent_after_decimal_point;
         match tri!(self.peek_or_null()) {
             b'e' | b'E' => self.parse_exponent(positive, significand, exponent),
             _ => self.f64_from_parts(positive, significand, exponent),