Do writeback of child expressions before parent expression

Author: compiler-errors

compiler/rustc_typeck/src/check/writeback.rs

@@ -263,8 +263,6 @@ impl<'cx, 'tcx> Visitor<'tcx> for WritebackCx<'cx, 'tcx> {
         self.fix_scalar_builtin_expr(e);
         self.fix_index_builtin_expr(e);
 
-        self.visit_node_id(e.span, e.hir_id);
-
         match e.kind {
             hir::ExprKind::Closure(_, _, body, _, _) => {
                 let body = self.fcx.tcx.hir().body(body);
@@ -291,6 +289,7 @@ impl<'cx, 'tcx> Visitor<'tcx> for WritebackCx<'cx, 'tcx> {
             _ => {}
         }
 
+        self.visit_node_id(e.span, e.hir_id);
         intravisit::walk_expr(self, e);
     }
 

src/test/ui/type/type-check/unknown_type_for_closure.rs

@@ -1,3 +1,17 @@
-fn main() {
-    let x = |_| {    }; //~ ERROR type annotations needed
+fn infer_in_arg() {
+    let x = |b: Vec<_>| {}; //~ ERROR E0282
 }
+
+fn empty_pattern() {
+    let x = |_| {}; //~ ERROR type annotations needed
+}
+
+fn infer_ty() {
+    let x = |k: _| {}; //~ ERROR type annotations needed
+}
+
+fn ambig_return() {
+    let x = || -> Vec<_> { Vec::new() }; //~ ERROR type annotations needed for the closure `fn() -> Vec<_>`
+}
+
+fn main() {}

src/test/ui/type/type-check/unknown_type_for_closure.stderr

@@ -1,9 +1,32 @@
-error[E0282]: type annotations needed
+error[E0282]: type annotations needed for `Vec<_>`
   --> $DIR/unknown_type_for_closure.rs:2:14
    |
-LL |     let x = |_| {    };
+LL |     let x = |b: Vec<_>| {};
    |              ^ consider giving this closure parameter a type
 
-error: aborting due to previous error
+error[E0282]: type annotations needed
+  --> $DIR/unknown_type_for_closure.rs:6:14
+   |
+LL |     let x = |_| {};
+   |              ^ consider giving this closure parameter a type
+
+error[E0282]: type annotations needed
+  --> $DIR/unknown_type_for_closure.rs:10:14
+   |
+LL |     let x = |k: _| {};
+   |              ^ consider giving this closure parameter a type
+
+error[E0282]: type annotations needed for the closure `fn() -> Vec<_>`
+  --> $DIR/unknown_type_for_closure.rs:14:28
+   |
+LL |     let x = || -> Vec<_> { Vec::new() };
+   |                            ^^^^^^^^ cannot infer type for type parameter `T`
+   |
+help: give this closure an explicit return type without `_` placeholders
+   |
+LL |     let x = || -> Vec<_> { Vec::new() };
+   |                   ~~~~~~
+
+error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0282`.