Add doc comments

Author: Aaron1011

src/librustc_ast/ast.rs

@@ -1165,7 +1165,7 @@ pub enum ExprKind {
     /// and the remaining elements are the rest of the arguments.
     /// Thus, `x.foo::<Bar, Baz>(a, b, c, d)` is represented as
     /// `ExprKind::MethodCall(PathSegment { foo, [Bar, Baz] }, [x, a, b, c, d])`.
-    /// The `Span` is the span of the function, without the dot and receiver
+    /// This `Span` is the span of the function, without the dot and receiver
     /// (e.g. `foo(a, b)` in `x.foo(a, b)`
     MethodCall(PathSegment, Vec<P<Expr>>, Span),
     /// A tuple (e.g., `(a, b, c, d)`).

src/librustc_middle/mir/mod.rs

@@ -1131,6 +1131,8 @@ pub enum TerminatorKind<'tcx> {
         /// `true` if this is from a call in HIR rather than from an overloaded
         /// operator. True for overloaded function call.
         from_hir_call: bool,
+        /// This `Span` is the span of the function, without the dot and receiver
+        /// (e.g. `foo(a, b)` in `x.foo(a, b)`
         fn_span: Span,
     },
 

src/librustc_mir_build/hair/mod.rs

@@ -146,6 +146,8 @@ crate enum ExprKind<'tcx> {
         // Whether this is from a call in HIR, rather than from an overloaded
         // operator. True for overloaded function call.
         from_hir_call: bool,
+        /// This `Span` is the span of the function, without the dot and receiver
+        /// (e.g. `foo(a, b)` in `x.foo(a, b)`
         fn_span: Span,
     },
     Deref {