From c0e87f13a4d2f6fcef92c8c01bdc8dda9e0549a5 Mon Sep 17 00:00:00 2001
From: varkor <github@varkor.com>
Date: Thu, 15 Feb 2018 15:54:40 +0000
Subject: [PATCH] Make ".e0" not parse as 0.0

This forces floats to have either a digit before the separating point, or after. Thus ".e0" is invalid like ".", when using `parse()`.
---
 src/libcore/num/dec2flt/parse.rs     | 3 ++-
 src/libcore/tests/num/dec2flt/mod.rs | 6 ++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/libcore/num/dec2flt/parse.rs b/src/libcore/num/dec2flt/parse.rs
index d20986faa0fc..69418434ebea 100644
--- a/src/libcore/num/dec2flt/parse.rs
+++ b/src/libcore/num/dec2flt/parse.rs
@@ -73,7 +73,8 @@ pub fn parse_decimal(s: &str) -> ParseResult {
         }
         Some(&b'.') => {
             let (fractional, s) = eat_digits(&s[1..]);
-            if integral.is_empty() && fractional.is_empty() && s.is_empty() {
+            if integral.is_empty() && fractional.is_empty() {
+                // We require at least a single digit before or after the point.
                 return Invalid;
             }
 
diff --git a/src/libcore/tests/num/dec2flt/mod.rs b/src/libcore/tests/num/dec2flt/mod.rs
index 9934e1dab966..17b2f59cd4df 100644
--- a/src/libcore/tests/num/dec2flt/mod.rs
+++ b/src/libcore/tests/num/dec2flt/mod.rs
@@ -101,6 +101,12 @@ fn lonely_dot() {
     assert!(".".parse::<f64>().is_err());
 }
 
+#[test]
+fn exponentiated_dot() {
+    assert!(".e0".parse::<f32>().is_err());
+    assert!(".e0".parse::<f64>().is_err());
+}
+
 #[test]
 fn lonely_sign() {
     assert!("+".parse::<f32>().is_err());