expressions.md: Attempt fixing broken grammar in Mutability paragraph
@@ -206,7 +206,7 @@ The following expressions can be mutable place expression contexts:
* Dereference of a variable, or field of a variable, with type `&mut T`. Note:
This is an exception to the requirement of the next rule.
* Dereferences of a type that implements `DerefMut`: this then requires that
- the value being dereferenced is evaluated is a mutable place expression context.
+ the value being dereferenced is evaluated in a mutable place expression context.
* [Array indexing] of a type that implements `IndexMut`: this
then evaluates the value being indexed, but not the index, in mutable place
expression context.
