FromPrimitive: fix some comments

While the meaning was clear from context, the terms "value" and "type"
were inverted for some method comments.

Adopted the third person singular present indicative form for the
summary lines ("Converts" rather than "Convert").

src/cast.rs

@@ -362,44 +362,44 @@ impl_to_primitive_float!(f64);
 
 /// A generic trait for converting a number to a value.
 pub trait FromPrimitive: Sized {
-    /// Convert an `isize` to return an optional value of this type. If the
-    /// value cannot be represented by this value, then `None` is returned.
+    /// Converts an `isize` to return an optional value of this type. If the
+    /// value cannot be represented by this type, then `None` is returned.
     #[inline]
     fn from_isize(n: isize) -> Option<Self> {
         n.to_i64().and_then(FromPrimitive::from_i64)
     }
 
-    /// Convert an `i8` to return an optional value of this type. If the
-    /// type cannot be represented by this value, then `None` is returned.
+    /// Converts an `i8` to return an optional value of this type. If the
+    /// value cannot be represented by this type, then `None` is returned.
     #[inline]
     fn from_i8(n: i8) -> Option<Self> {
         FromPrimitive::from_i64(From::from(n))
     }
 
-    /// Convert an `i16` to return an optional value of this type. If the
-    /// type cannot be represented by this value, then `None` is returned.
+    /// Converts an `i16` to return an optional value of this type. If the
+    /// value cannot be represented by this type, then `None` is returned.
     #[inline]
     fn from_i16(n: i16) -> Option<Self> {
         FromPrimitive::from_i64(From::from(n))
     }
 
-    /// Convert an `i32` to return an optional value of this type. If the
-    /// type cannot be represented by this value, then `None` is returned.
+    /// Converts an `i32` to return an optional value of this type. If the
+    /// value cannot be represented by this type, then `None` is returned.
     #[inline]
     fn from_i32(n: i32) -> Option<Self> {
         FromPrimitive::from_i64(From::from(n))
     }
 
-    /// Convert an `i64` to return an optional value of this type. If the
-    /// type cannot be represented by this value, then `None` is returned.
+    /// Converts an `i64` to return an optional value of this type. If the
+    /// value cannot be represented by this type, then `None` is returned.
     fn from_i64(n: i64) -> Option<Self>;
 
-    /// Convert an `i128` to return an optional value of this type. If the
-    /// type cannot be represented by this value, then `None` is returned.
+    /// Converts an `i128` to return an optional value of this type. If the
+    /// value cannot be represented by this type, then `None` is returned.
     ///
     /// This method is only available with feature `i128` enabled on Rust >= 1.26.
     ///
-    /// The default implementation converts through `from_i64()`.  Types implementing
+    /// The default implementation converts through `from_i64()`. Types implementing
     /// this trait should override this method if they can represent a greater range.
     #[inline]
     #[cfg(has_i128)]
@@ -407,44 +407,44 @@ pub trait FromPrimitive: Sized {
         n.to_i64().and_then(FromPrimitive::from_i64)
     }
 
-    /// Convert a `usize` to return an optional value of this type. If the
-    /// type cannot be represented by this value, then `None` is returned.
+    /// Converts a `usize` to return an optional value of this type. If the
+    /// value cannot be represented by this type, then `None` is returned.
     #[inline]
     fn from_usize(n: usize) -> Option<Self> {
         n.to_u64().and_then(FromPrimitive::from_u64)
     }
 
-    /// Convert an `u8` to return an optional value of this type. If the
-    /// type cannot be represented by this value, then `None` is returned.
+    /// Converts an `u8` to return an optional value of this type. If the
+    /// value cannot be represented by this type, then `None` is returned.
     #[inline]
     fn from_u8(n: u8) -> Option<Self> {
         FromPrimitive::from_u64(From::from(n))
     }
 
-    /// Convert an `u16` to return an optional value of this type. If the
-    /// type cannot be represented by this value, then `None` is returned.
+    /// Converts an `u16` to return an optional value of this type. If the
+    /// value cannot be represented by this type, then `None` is returned.
     #[inline]
     fn from_u16(n: u16) -> Option<Self> {
         FromPrimitive::from_u64(From::from(n))
     }
 
-    /// Convert an `u32` to return an optional value of this type. If the
-    /// type cannot be represented by this value, then `None` is returned.
+    /// Converts an `u32` to return an optional value of this type. If the
+    /// value cannot be represented by this type, then `None` is returned.
     #[inline]
     fn from_u32(n: u32) -> Option<Self> {
         FromPrimitive::from_u64(From::from(n))
     }
 
-    /// Convert an `u64` to return an optional value of this type. If the
-    /// type cannot be represented by this value, then `None` is returned.
+    /// Converts an `u64` to return an optional value of this type. If the
+    /// value cannot be represented by this type, then `None` is returned.
     fn from_u64(n: u64) -> Option<Self>;
 
-    /// Convert an `u128` to return an optional value of this type. If the
-    /// type cannot be represented by this value, then `None` is returned.
+    /// Converts an `u128` to return an optional value of this type. If the
+    /// value cannot be represented by this type, then `None` is returned.
     ///
     /// This method is only available with feature `i128` enabled on Rust >= 1.26.
     ///
-    /// The default implementation converts through `from_u64()`.  Types implementing
+    /// The default implementation converts through `from_u64()`. Types implementing
     /// this trait should override this method if they can represent a greater range.
     #[inline]
     #[cfg(has_i128)]
@@ -452,15 +452,15 @@ pub trait FromPrimitive: Sized {
         n.to_u64().and_then(FromPrimitive::from_u64)
     }
 
-    /// Convert a `f32` to return an optional value of this type. If the
-    /// type cannot be represented by this value, then `None` is returned.
+    /// Converts a `f32` to return an optional value of this type. If the
+    /// value cannot be represented by this type, then `None` is returned.
     #[inline]
     fn from_f32(n: f32) -> Option<Self> {
         FromPrimitive::from_f64(From::from(n))
     }
 
-    /// Convert a `f64` to return an optional value of this type. If the
-    /// type cannot be represented by this value, then `None` is returned.
+    /// Converts a `f64` to return an optional value of this type. If the
+    /// value cannot be represented by this type, then `None` is returned.
     #[inline]
     fn from_f64(n: f64) -> Option<Self> {
         match n.to_i64() {