Rollup merge of #142976 - compiler-errors:coerce-ice, r=fee1-dead

Check CoerceUnsized impl validity before coercing

Self-explanatory from the title.

Fixes rust-lang/rust#126982
Fixes rust-lang/rust#131048
Fixes rust-lang/rust#134217
Fixes rust-lang/rust#126269
Fixes rust-lang/rust#138265

7 files changed, 32 insertions, 58 deletions

diff --git a/tests/crashes/126269.rs b/tests/crashes/126269.rs
deleted file mode 100644
index ca4b76eb930..00000000000
--- a/tests/crashes/126269.rs
+++ /dev/null
@@ -1,12 +0,0 @@
-//@ known-bug: rust-lang/rust#126269
-#![feature(coerce_unsized)]
-
-pub enum Foo<T> {
-    Bar([T; usize::MAX]),
-}
-
-use std::ops::CoerceUnsized;
-
-impl<T, U> CoerceUnsized<U> for T {}
-
-fn main() {}
diff --git a/tests/crashes/126982.rs b/tests/crashes/126982.rs
deleted file mode 100644
index 8522d9415eb..00000000000
--- a/tests/crashes/126982.rs
+++ /dev/null
@@ -1,18 +0,0 @@
-//@ known-bug: rust-lang/rust#126982
-
-#![feature(coerce_unsized)]
-use std::ops::CoerceUnsized;
-
-struct Foo<T: ?Sized> {
-    a: T,
-}
-
-impl<T, U> CoerceUnsized<U> for Foo<T> {}
-
-union U {
-    a: usize,
-}
-
-const C: U = Foo { a: 10 };
-
-fn main() {}
diff --git a/tests/crashes/131048.rs b/tests/crashes/131048.rs
deleted file mode 100644
index d57e9921a8a..00000000000
--- a/tests/crashes/131048.rs
+++ /dev/null
@@ -1,7 +0,0 @@
-//@ known-bug: #131048
-
-impl<A> std::ops::CoerceUnsized<A> for A {}
-
-fn main() {
-    format_args!("Hello, world!");
-}
diff --git a/tests/crashes/134217.rs b/tests/crashes/134217.rs
deleted file mode 100644
index 1b14c660e8b..00000000000
--- a/tests/crashes/134217.rs
+++ /dev/null
@@ -1,9 +0,0 @@
-//@ known-bug: #134217
-
-impl<A> std::ops::CoerceUnsized<A> for A {}
-
-fn main() {
-    if let _ = true
-        && true
-    {}
-}
diff --git a/tests/crashes/138265.rs b/tests/crashes/138265.rs
deleted file mode 100644
index f6c8ea74889..00000000000
--- a/tests/crashes/138265.rs
+++ /dev/null
@@ -1,12 +0,0 @@
-//@ known-bug: #138265
-
-#![feature(coerce_unsized)]
-#![crate_type = "lib"]
-impl<A> std::ops::CoerceUnsized<A> for A {}
-pub fn f() {
-    [0; {
-        let mut c = &0;
-        c = &0;
-        0
-    }]
-}
diff --git a/tests/ui/coercion/invalid-blanket-coerce-unsized-impl.rs b/tests/ui/coercion/invalid-blanket-coerce-unsized-impl.rs
new file mode 100644
index 00000000000..a4fd7710718
--- /dev/null
+++ b/tests/ui/coercion/invalid-blanket-coerce-unsized-impl.rs
@@ -0,0 +1,13 @@
+// Regression test minimized from #126982.
+// We used to apply a coerce_unsized coercion to literally every argument since
+// the blanket applied in literally all cases, even though it was incoherent.
+
+#![feature(coerce_unsized)]
+
+impl<A> std::ops::CoerceUnsized<A> for A {}
+//~^ ERROR type parameter `A` must be used as the type parameter for some local type
+//~| ERROR the trait `CoerceUnsized` may only be implemented for a coercion between structures
+
+const C: usize = 1;
+
+fn main() {}
diff --git a/tests/ui/coercion/invalid-blanket-coerce-unsized-impl.stderr b/tests/ui/coercion/invalid-blanket-coerce-unsized-impl.stderr
new file mode 100644
index 00000000000..377906ee334
--- /dev/null
+++ b/tests/ui/coercion/invalid-blanket-coerce-unsized-impl.stderr
@@ -0,0 +1,19 @@
+error[E0210]: type parameter `A` must be used as the type parameter for some local type (e.g., `MyStruct<A>`)
+  --> $DIR/invalid-blanket-coerce-unsized-impl.rs:7:6
+   |
+LL | impl<A> std::ops::CoerceUnsized<A> for A {}
+   |      ^ type parameter `A` must be used as the type parameter for some local type
+   |
+   = note: implementing a foreign trait is only possible if at least one of the types for which it is implemented is local
+   = note: only traits defined in the current crate can be implemented for a type parameter
+
+error[E0377]: the trait `CoerceUnsized` may only be implemented for a coercion between structures
+  --> $DIR/invalid-blanket-coerce-unsized-impl.rs:7:1
+   |
+LL | impl<A> std::ops::CoerceUnsized<A> for A {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0210, E0377.
+For more information about an error, try `rustc --explain E0210`.