Make float parsing "." return Err

Toby Scrace · Toby Scrace · commit 33f3c52d32e6 · 2016-01-04T18:23:33.000Z
This makes both of the following return Err:

    ".".parse::&lt;f32&gt;()
    ".".parse::&lt;f64&gt;()

This is a [breaking-change], which the libs team have classified as a
bug fix.
diff --git a/src/libcore/num/dec2flt/parse.rs b/src/libcore/num/dec2flt/parse.rs
@@ -56,27 +56,28 @@ pub enum ParseResult<'a> {
 /// Check if the input string is a valid floating point number and if so, locate the integral
 /// part, the fractional part, and the exponent in it. Does not handle signs.
 pub fn parse_decimal(s: &str) -> ParseResult {
+    if s.is_empty() {
+        return Invalid;
+    }
+
     let s = s.as_bytes();
     let (integral, s) = eat_digits(s);
+
     match s.first() {
-        None => {
-            if integral.is_empty() {
-                return Invalid; // No digits at all
-            }
-            Valid(Decimal::new(integral, b"", 0))
-        }
+        None => Valid(Decimal::new(integral, b"", 0)),
         Some(&b'e') | Some(&b'E') => {
             if integral.is_empty() {
                 return Invalid; // No digits before 'e'
             }
+
             parse_exp(integral, b"", &s[1..])
         }
         Some(&b'.') => {
             let (fractional, s) = eat_digits(&s[1..]);
             if integral.is_empty() && fractional.is_empty() && s.is_empty() {
-                // For historic reasons "." is a valid input.
-                return Valid(Decimal::new(b"", b"", 0));
+                return Invalid;
             }
+
             match s.first() {
                 None => Valid(Decimal::new(integral, fractional, 0)),
                 Some(&b'e') | Some(&b'E') => parse_exp(integral, fractional, &s[1..]),
diff --git a/src/libcoretest/num/dec2flt/mod.rs b/src/libcoretest/num/dec2flt/mod.rs
@@ -98,7 +98,8 @@ fn fast_path_correct() {
 
 #[test]
 fn lonely_dot() {
-    assert_eq!(".".parse(), Ok(0.0));
+    assert!(".".parse::<f32>().is_err());
+    assert!(".".parse::<f64>().is_err());
 }
 
 #[test]

Original file line number	Diff line number	Diff line change
`@@ -98,7 +98,8 @@ fn fast_path_correct() {`
`98`	`98`
`99`	`99`	`#[test]`
`100`	`100`	`fn lonely_dot() {`
`101`		`- assert_eq!(".".parse(), Ok(0.0));`
	`101`	`+ assert!(".".parse::<f32>().is_err());`
	`102`	`+ assert!(".".parse::<f64>().is_err());`
`102`	`103`	`}`
`103`	`104`
`104`	`105`	`#[test]`