Implement `#[define_opaque]` attribute for functions.

2 files changed, 46 insertions, 40 deletions

diff --git a/tests/ui/pattern/usefulness/impl-trait.rs b/tests/ui/pattern/usefulness/impl-trait.rs
index 16560a09267..47cee17b579 100644
--- a/tests/ui/pattern/usefulness/impl-trait.rs
+++ b/tests/ui/pattern/usefulness/impl-trait.rs
@@ -25,6 +25,7 @@ fn friend_of_return_never_rpit(x: Void) {
 }
 
 type T = impl Copy;
+#[define_opaque(T)]
 fn return_never_tait(x: Void) -> T {
     if false {
         match return_never_tait(x) {
@@ -88,6 +89,7 @@ fn inner_tuple() {
 }
 
 type U = impl Copy;
+#[define_opaque(U)]
 fn unify_never(x: Void, u: U) -> U {
     if false {
         match u {
@@ -98,6 +100,7 @@ fn unify_never(x: Void, u: U) -> U {
 }
 
 type V = impl Copy;
+#[define_opaque(V)]
 fn infer_in_match(x: Option<V>) {
     match x {
         None => {}
@@ -116,6 +119,7 @@ struct Rec<'a> {
     n: u32,
     w: Option<&'a W>,
 }
+#[define_opaque(W)]
 fn recursive_opaque() -> W {
     if false {
         match recursive_opaque() {
@@ -130,6 +134,7 @@ fn recursive_opaque() -> W {
 
 type X = impl Copy;
 struct SecretelyVoid(X);
+#[define_opaque(X)]
 fn nested_empty_opaque(x: Void) -> X {
     if false {
         let opaque_void = nested_empty_opaque(x);
@@ -143,6 +148,7 @@ fn nested_empty_opaque(x: Void) -> X {
 
 type Y = (impl Copy, impl Copy);
 struct SecretelyDoubleVoid(Y);
+#[define_opaque(Y)]
 fn super_nested_empty_opaque(x: Void) -> Y {
     if false {
         let opaque_void = super_nested_empty_opaque(x);
diff --git a/tests/ui/pattern/usefulness/impl-trait.stderr b/tests/ui/pattern/usefulness/impl-trait.stderr
index c3e1c267b61..62045151968 100644
--- a/tests/ui/pattern/usefulness/impl-trait.stderr
+++ b/tests/ui/pattern/usefulness/impl-trait.stderr
@@ -15,7 +15,7 @@ LL | #![deny(unreachable_patterns)]
    |         ^^^^^^^^^^^^^^^^^^^^
 
 error: unreachable pattern
-  --> $DIR/impl-trait.rs:31:13
+  --> $DIR/impl-trait.rs:32:13
    |
 LL |             _ => {}
    |             ^------
@@ -25,22 +25,8 @@ LL |             _ => {}
    |
    = note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
 
-error[E0004]: non-exhaustive patterns: type `impl Copy` is non-empty
-  --> $DIR/impl-trait.rs:23:11
-   |
-LL |     match return_never_rpit(x) {}
-   |           ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: the matched value is of type `impl Copy`
-help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown
-   |
-LL ~     match return_never_rpit(x) {
-LL +         _ => todo!(),
-LL ~     }
-   |
-
 error: unreachable pattern
-  --> $DIR/impl-trait.rs:45:13
+  --> $DIR/impl-trait.rs:46:13
    |
 LL |             Some(_) => {}
    |             ^^^^^^^------
@@ -51,7 +37,7 @@ LL |             Some(_) => {}
    = note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
 
 error: unreachable pattern
-  --> $DIR/impl-trait.rs:49:13
+  --> $DIR/impl-trait.rs:50:13
    |
 LL |             None => {}
    |             ---- matches all the relevant values
@@ -59,7 +45,7 @@ LL |             _ => {}
    |             ^ no value can reach this
 
 error: unreachable pattern
-  --> $DIR/impl-trait.rs:59:13
+  --> $DIR/impl-trait.rs:60:13
    |
 LL |             Some(_) => {}
    |             ^^^^^^^------
@@ -70,7 +56,7 @@ LL |             Some(_) => {}
    = note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
 
 error: unreachable pattern
-  --> $DIR/impl-trait.rs:63:13
+  --> $DIR/impl-trait.rs:64:13
    |
 LL |             None => {}
    |             ---- matches all the relevant values
@@ -78,7 +64,7 @@ LL |             _ => {}
    |             ^ no value can reach this
 
 error: unreachable pattern
-  --> $DIR/impl-trait.rs:76:9
+  --> $DIR/impl-trait.rs:77:9
    |
 LL |         _ => {}
    |         ^------
@@ -89,7 +75,7 @@ LL |         _ => {}
    = note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
 
 error: unreachable pattern
-  --> $DIR/impl-trait.rs:86:9
+  --> $DIR/impl-trait.rs:87:9
    |
 LL |         _ => {}
    |         - matches any value
@@ -97,7 +83,7 @@ LL |         Some((a, b)) => {}
    |         ^^^^^^^^^^^^ no value can reach this
 
 error: unreachable pattern
-  --> $DIR/impl-trait.rs:94:13
+  --> $DIR/impl-trait.rs:96:13
    |
 LL |             _ => {}
    |             ^------
@@ -107,22 +93,8 @@ LL |             _ => {}
    |
    = note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
 
-error[E0004]: non-exhaustive patterns: type `T` is non-empty
-  --> $DIR/impl-trait.rs:37:11
-   |
-LL |     match return_never_tait(x) {}
-   |           ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: the matched value is of type `T`
-help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown
-   |
-LL ~     match return_never_tait(x) {
-LL +         _ => todo!(),
-LL ~     }
-   |
-
 error: unreachable pattern
-  --> $DIR/impl-trait.rs:105:9
+  --> $DIR/impl-trait.rs:108:9
    |
 LL |         Some((a, b)) => {}
    |         ------------ matches all the relevant values
@@ -130,7 +102,7 @@ LL |         Some((mut x, mut y)) => {
    |         ^^^^^^^^^^^^^^^^^^^^ no value can reach this
 
 error: unreachable pattern
-  --> $DIR/impl-trait.rs:124:13
+  --> $DIR/impl-trait.rs:128:13
    |
 LL |             _ => {}
    |             - matches any value
@@ -138,7 +110,7 @@ LL |             Rec { n: 0, w: Some(Rec { n: 0, w: _ }) } => {}
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ no value can reach this
 
 error: unreachable pattern
-  --> $DIR/impl-trait.rs:138:13
+  --> $DIR/impl-trait.rs:143:13
    |
 LL |             _ => {}
    |             ^------
@@ -149,7 +121,7 @@ LL |             _ => {}
    = note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
 
 error: unreachable pattern
-  --> $DIR/impl-trait.rs:151:13
+  --> $DIR/impl-trait.rs:157:13
    |
 LL |             _ => {}
    |             ^------
@@ -159,6 +131,34 @@ LL |             _ => {}
    |
    = note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
 
+error[E0004]: non-exhaustive patterns: type `impl Copy` is non-empty
+  --> $DIR/impl-trait.rs:23:11
+   |
+LL |     match return_never_rpit(x) {}
+   |           ^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: the matched value is of type `impl Copy`
+help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown
+   |
+LL ~     match return_never_rpit(x) {
+LL +         _ => todo!(),
+LL ~     }
+   |
+
+error[E0004]: non-exhaustive patterns: type `T` is non-empty
+  --> $DIR/impl-trait.rs:38:11
+   |
+LL |     match return_never_tait(x) {}
+   |           ^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: the matched value is of type `T`
+help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown
+   |
+LL ~     match return_never_tait(x) {
+LL +         _ => todo!(),
+LL ~     }
+   |
+
 error: aborting due to 15 previous errors
 
 For more information about this error, try `rustc --explain E0004`.