Refactor Adjust and CastKind

src/librustc_mir/hair/cx/expr.rs

@@ -68,6 +68,26 @@ impl<'tcx> Mirror<'tcx> for &'tcx hir::Expr {
     }
 }
 
+/// Adjust the span from the block, to the last expression of the
+/// block. This is a better span when returning a mutable reference
+/// with too short a lifetime. The error message will use the span
+/// from the assignment to the return place, which should only point
+/// at the returned value, not the entire function body.
+///
+/// fn return_short_lived<'a>(x: &'a mut i32) -> &'static mut i32 {
+///      x
+///   // ^ error message points at this expression.
+/// }
+fn adjust_span<'tcx>(expr: &mut Expr<'tcx>) -> Span {
+    if let ExprKind::Block { body } = expr.kind {
+        if let Some(ref last_expr) = body.expr {
+            expr.span = last_expr.span;
+        }
+    }
+
+    expr.span
+}
+
 fn apply_adjustment<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
                                     hir_expr: &'tcx hir::Expr,
                                     mut expr: Expr<'tcx>,
@@ -76,12 +96,7 @@ fn apply_adjustment<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
     let Expr { temp_lifetime, mut span, .. } = expr;
     let kind = match adjustment.kind {
         Adjust::Pointer(PointerCast::Unsize) => {
-            if let ExprKind::Block { body } = expr.kind {
-                if let Some(ref last_expr) = body.expr {
-                    span = last_expr.span;
-                    expr.span = span;
-                }
-            }
+            span = adjust_span(&mut expr);
             ExprKind::Pointer { cast: PointerCast::Unsize, source: expr.to_ref() }
         }
         Adjust::Pointer(cast) => {
@@ -91,28 +106,12 @@ fn apply_adjustment<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
             ExprKind::NeverToAny { source: expr.to_ref() }
         }
         Adjust::Deref(None) => {
-            // Adjust the span from the block, to the last expression of the
-            // block. This is a better span when returning a mutable reference
-            // with too short a lifetime. The error message will use the span
-            // from the assignment to the return place, which should only point
-            // at the returned value, not the entire function body.
-            //
-            // fn return_short_lived<'a>(x: &'a mut i32) -> &'static mut i32 {
-            //      x
-            //   // ^ error message points at this expression.
-            // }
-            //
-            // We don't need to do this adjustment in the next match arm since
-            // deref coercions always start with a built-in deref.
-            if let ExprKind::Block { body } = expr.kind {
-                if let Some(ref last_expr) = body.expr {
-                    span = last_expr.span;
-                    expr.span = span;
-                }
-            }
+            span = adjust_span(&mut expr);
             ExprKind::Deref { arg: expr.to_ref() }
         }
         Adjust::Deref(Some(deref)) => {
+            // We don't need to do call adjust_span here since
+            // deref coercions always start with a built-in deref.
             let call = deref.method_call(cx.tcx(), expr.ty);
 
             expr = Expr {