more-logical approach for drilling into types

Author: Nathan-Fenner

compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs

@@ -1,4 +1,5 @@
 mod _impl;
+mod adjust_fulfillment_errors;
 mod arg_matrix;
 mod checks;
 mod suggestions;

compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs

@@ -35,16 +35,14 @@ trait Ty<'a> {
 }
 
 fn main() {
-    let v = Unit2.m(
-        L {
-            //~^ ERROR type mismatch
-            f: |x| {
-                //~^ ERROR to be a closure that returns `Unit3`, but it returns `Unit4`
-                drop(x);
-                Unit4
-            },
+    let v = Unit2.m(L {
+        //~^ ERROR type mismatch
+        //~| ERROR to be a closure that returns `Unit3`, but it returns `Unit4`
+        f: |x| {
+            drop(x);
+            Unit4
         },
-    );
+    });
 }
 
 impl<'a> Ty<'a> for Unit2 {

compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs

@@ -1,16 +1,17 @@
-error[E0271]: type mismatch resolving `for<'r> <L<[closure@$DIR/issue-62203-hrtb-ice.rs:41:16: 41:19]> as T0<'r, (&'r u8,)>>::O == <_ as Ty<'r>>::V`
-  --> $DIR/issue-62203-hrtb-ice.rs:39:9
+error[E0271]: type mismatch resolving `for<'r> <L<[closure@$DIR/issue-62203-hrtb-ice.rs:41:12: 41:15]> as T0<'r, (&'r u8,)>>::O == <_ as Ty<'r>>::V`
+  --> $DIR/issue-62203-hrtb-ice.rs:38:21
    |
-LL |       let v = Unit2.m(
-   |                     - required by a bound introduced by this call
-LL | /         L {
+LL |       let v = Unit2.m(L {
+   |  ___________________-_^
+   | |                   |
+   | |                   required by a bound introduced by this call
 LL | |
-LL | |             f: |x| {
 LL | |
+LL | |         f: |x| {
 ...  |
-LL | |             },
 LL | |         },
-   | |_________^ type mismatch resolving `for<'r> <L<[closure@$DIR/issue-62203-hrtb-ice.rs:41:16: 41:19]> as T0<'r, (&'r u8,)>>::O == <_ as Ty<'r>>::V`
+LL | |     });
+   | |_____^ type mismatch resolving `for<'r> <L<[closure@$DIR/issue-62203-hrtb-ice.rs:41:12: 41:15]> as T0<'r, (&'r u8,)>>::O == <_ as Ty<'r>>::V`
    |
 note: expected this to be `<_ as Ty<'_>>::V`
   --> $DIR/issue-62203-hrtb-ice.rs:21:14
@@ -30,21 +31,22 @@ LL |     where
 LL |         F: for<'r> T0<'r, (<Self as Ty<'r>>::V,), O = <B as Ty<'r>>::V>,
    |                                                   ^^^^^^^^^^^^^^^^^^^^ required by this bound in `T1::m`
 
-error[E0271]: expected `[[email protected]:41:16]` to be a closure that returns `Unit3`, but it returns `Unit4`
-  --> $DIR/issue-62203-hrtb-ice.rs:41:16
-   |
-LL |       let v = Unit2.m(
-   |                     - required by a bound introduced by this call
-...
-LL |               f: |x| {
-   |  ________________^
+error[E0271]: expected `[[email protected]:41:12]` to be a closure that returns `Unit3`, but it returns `Unit4`
+  --> $DIR/issue-62203-hrtb-ice.rs:38:21
+   |
+LL |       let v = Unit2.m(L {
+   |  ___________________-_^
+   | |                   |
+   | |                   required by a bound introduced by this call
+LL | |
 LL | |
-LL | |                 drop(x);
-LL | |                 Unit4
-LL | |             },
-   | |_____________^ expected struct `Unit3`, found struct `Unit4`
+LL | |         f: |x| {
+...  |
+LL | |         },
+LL | |     });
+   | |_____^ expected struct `Unit3`, found struct `Unit4`
    |
-note: required for `L<[closure@$DIR/issue-62203-hrtb-ice.rs:41:16: 41:19]>` to implement `for<'r> T0<'r, (&'r u8,)>`
+note: required for `L<[closure@$DIR/issue-62203-hrtb-ice.rs:41:12: 41:15]>` to implement `for<'r> T0<'r, (&'r u8,)>`
   --> $DIR/issue-62203-hrtb-ice.rs:17:16
    |
 LL | impl<'a, A, T> T0<'a, A> for L<T>

src/test/ui/higher-rank-trait-bounds/issue-62203-hrtb-ice.rs

@@ -48,6 +48,7 @@ impl<X, Y: T3> T2 for GenericBurrito<X, Y> {}
 struct NotSpicy;
 
 impl<A: T3, B: T3> T2 for (A, B) {}
+impl<A: T2, B: T2> T1 for (A, B) {}
 
 fn want<V: T1>(_x: V) {}
 
@@ -64,6 +65,12 @@ struct Two<A, B> {
 
 impl<X, Y: T1, Z> T1 for Two<Two<X, Y>, Z> {}
 
+struct DoubleWrapper<T> {
+    item: Wrapper<T>,
+}
+
+impl<T: T1> T1 for DoubleWrapper<T> {}
+
 fn example<Q>(q: Q) {
     // In each of the following examples, we expect the error span to point at the 'q' variable,
     // since the missing constraint is `Q: T3`.
@@ -89,9 +96,23 @@ fn example<Q>(q: Q) {
     //~^ ERROR the trait bound `Q: T3` is not satisfied [E0277]
 
     // Verifies for tuple:
+    want((3, q));
+    //~^ ERROR the trait bound `Q: T2` is not satisfied [E0277]
+
+    // Verifies for nested tuple:
     want(Wrapper { value: (3, q) });
     //~^ ERROR the trait bound `Q: T3` is not satisfied [E0277]
 
+    // Verifies for nested tuple:
+    want(((3, q), 5));
+    //~^ ERROR the trait bound `Q: T3` is not satisfied [E0277]
+
+    want(DoubleWrapper { item: Wrapper { value: q } });
+    //~^ ERROR the trait bound `Q: T1` is not satisfied [E0277]
+
+    want(DoubleWrapper { item: Wrapper { value: DoubleWrapper { item: Wrapper { value: q } } } });
+    //~^ ERROR the trait bound `Q: T1` is not satisfied [E0277]
+
     // Verifies for type alias to struct:
     want(Wrapper { value: AliasBurrito { spiciness: q, filling: q } });
     //~^ ERROR the trait bound `Q: T3` is not satisfied [E0277]