update comment

Author: nikomatsakis

src/librustc/hir/mod.rs

@@ -926,7 +926,7 @@ pub enum Expr_ {
     ExprType(P<Expr>, P<Ty>),
     /// An `if` block, with an optional else block
     ///
-    /// `if expr { block } else { expr }`
+    /// `if expr { expr } else { expr }`
     ExprIf(P<Expr>, P<Expr>, Option<P<Expr>>),
     /// A while loop, with an optional label
     ///