Rollup merge of #66651 - Areredify:on-unimplemented-scope, r=davidtwco

Add `enclosing scope` parameter to `rustc_on_unimplemented`

Adds a new parameter to `#[rustc_on_unimplemented]`, `enclosing scope`, which highlights the function or closure scope with a message.

The wip part refers to adding this annotation to `Try` trait to improve ergonomics (which I don't know how to do since I change both std and librustc)

Closes #61709.

2 files changed, 93 insertions, 0 deletions

diff --git a/src/test/ui/on-unimplemented/enclosing-scope.rs b/src/test/ui/on-unimplemented/enclosing-scope.rs
new file mode 100644
index 00000000000..881bff63f5f
--- /dev/null
+++ b/src/test/ui/on-unimplemented/enclosing-scope.rs
@@ -0,0 +1,27 @@
+// Test scope annotations from `enclosing_scope` parameter
+
+#![feature(rustc_attrs)]
+
+#[rustc_on_unimplemented(enclosing_scope="in this scope")]
+trait Trait{}
+
+struct Foo;
+
+fn f<T: Trait>(x: T) {}
+
+fn main() {
+    let x = || {
+        f(Foo{}); //~ ERROR the trait bound `Foo: Trait` is not satisfied
+        let y = || {
+            f(Foo{}); //~ ERROR the trait bound `Foo: Trait` is not satisfied
+        };
+    };
+
+    {
+        {
+            f(Foo{}); //~ ERROR the trait bound `Foo: Trait` is not satisfied
+        }
+    }
+
+    f(Foo{}); //~ ERROR the trait bound `Foo: Trait` is not satisfied
+}
diff --git a/src/test/ui/on-unimplemented/enclosing-scope.stderr b/src/test/ui/on-unimplemented/enclosing-scope.stderr
new file mode 100644
index 00000000000..092e560330b
--- /dev/null
+++ b/src/test/ui/on-unimplemented/enclosing-scope.stderr
@@ -0,0 +1,66 @@
+error[E0277]: the trait bound `Foo: Trait` is not satisfied
+  --> $DIR/enclosing-scope.rs:14:11
+   |
+LL |   fn f<T: Trait>(x: T) {}
+   |      -    ----- required by this bound in `f`
+...
+LL |       let x = || {
+   |  _____________-
+LL | |         f(Foo{});
+   | |           ^^^^^ the trait `Trait` is not implemented for `Foo`
+LL | |         let y = || {
+LL | |             f(Foo{});
+LL | |         };
+LL | |     };
+   | |_____- in this scope
+
+error[E0277]: the trait bound `Foo: Trait` is not satisfied
+  --> $DIR/enclosing-scope.rs:16:15
+   |
+LL |   fn f<T: Trait>(x: T) {}
+   |      -    ----- required by this bound in `f`
+...
+LL |           let y = || {
+   |  _________________-
+LL | |             f(Foo{});
+   | |               ^^^^^ the trait `Trait` is not implemented for `Foo`
+LL | |         };
+   | |_________- in this scope
+
+error[E0277]: the trait bound `Foo: Trait` is not satisfied
+  --> $DIR/enclosing-scope.rs:22:15
+   |
+LL |   fn f<T: Trait>(x: T) {}
+   |      -    ----- required by this bound in `f`
+LL | 
+LL | / fn main() {
+LL | |     let x = || {
+LL | |         f(Foo{});
+LL | |         let y = || {
+...  |
+LL | |             f(Foo{});
+   | |               ^^^^^ the trait `Trait` is not implemented for `Foo`
+...  |
+LL | |     f(Foo{});
+LL | | }
+   | |_- in this scope
+
+error[E0277]: the trait bound `Foo: Trait` is not satisfied
+  --> $DIR/enclosing-scope.rs:26:7
+   |
+LL |   fn f<T: Trait>(x: T) {}
+   |      -    ----- required by this bound in `f`
+LL | 
+LL | / fn main() {
+LL | |     let x = || {
+LL | |         f(Foo{});
+LL | |         let y = || {
+...  |
+LL | |     f(Foo{});
+   | |       ^^^^^ the trait `Trait` is not implemented for `Foo`
+LL | | }
+   | |_- in this scope
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0277`.