Rollup merge of #86775 - fee1-dead:impl-const-test, r=jonas-schievink

Test for const trait impls behind feature gates

 - Make the previous cross-crate tests use revisions instead of being separate files
 - Added test for gating const trait impls.

cc ``@oli-obk`` ``@jonas-schievink``

src/test/ui/rfc-2632-const-trait-impl/auxiliary/staged-api.rs

@@ -0,0 +1,22 @@
+#![feature(const_trait_impl)]
+#![allow(incomplete_features)]
+
+#![feature(staged_api)]
+#![stable(feature = "rust1", since = "1.0.0")]
+
+#[stable(feature = "rust1", since = "1.0.0")]
+pub trait MyTrait {
+    #[stable(feature = "rust1", since = "1.0.0")]
+    fn func();
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct Unstable;
+
+#[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_const_unstable(feature = "staged", issue = "none")]
+impl const MyTrait for Unstable {
+    fn func() {
+
+    }
+}

src/test/ui/rfc-2632-const-trait-impl/cross-crate-feature-disabled.rs

@@ -1,18 +0,0 @@
-// aux-build: cross-crate.rs
-extern crate cross_crate;
-
-use cross_crate::*;
-
-fn non_const_context() {
-    NonConst.func();
-    Const.func();
-}
-
-const fn const_context() {
-    NonConst.func();
-    //~^ ERROR: calls in constant functions are limited to constant functions, tuple structs and tuple variants
-    Const.func();
-    //~^ ERROR: calls in constant functions are limited to constant functions, tuple structs and tuple variants
-}
-
-fn main() {}

src/test/ui/rfc-2632-const-trait-impl/cross-crate.gated.stderr

@@ -1,5 +1,5 @@
 error[E0015]: calls in constant functions are limited to constant functions, tuple structs and tuple variants
-  --> $DIR/cross-crate-feature-enabled.rs:15:5
+  --> $DIR/cross-crate.rs:16:5
    |
 LL |     NonConst.func();
    |     ^^^^^^^^^^^^^^^

src/test/ui/rfc-2632-const-trait-impl/cross-crate.rs

@@ -1,4 +1,5 @@
-#![feature(const_trait_impl)]
+// revisions: stock gated
+#![cfg_attr(gated, feature(const_trait_impl))]
 #![allow(incomplete_features)]
 
 // aux-build: cross-crate.rs
@@ -15,6 +16,7 @@ const fn const_context() {
     NonConst.func();
     //~^ ERROR: calls in constant functions are limited to constant functions, tuple structs and tuple variants
     Const.func();
+    //[stock]~^ ERROR: calls in constant functions are limited to constant functions, tuple structs and tuple variants
 }
 
 fn main() {}

src/test/ui/rfc-2632-const-trait-impl/cross-crate.stock.stderr

@@ -1,11 +1,11 @@
 error[E0015]: calls in constant functions are limited to constant functions, tuple structs and tuple variants
-  --> $DIR/cross-crate-feature-disabled.rs:12:5
+  --> $DIR/cross-crate.rs:16:5
    |
 LL |     NonConst.func();
    |     ^^^^^^^^^^^^^^^
 
 error[E0015]: calls in constant functions are limited to constant functions, tuple structs and tuple variants
-  --> $DIR/cross-crate-feature-disabled.rs:14:5
+  --> $DIR/cross-crate.rs:18:5
    |
 LL |     Const.func();
    |     ^^^^^^^^^^^^

src/test/ui/rfc-2632-const-trait-impl/staged-api.rs

@@ -0,0 +1,39 @@
+// revisions: stock staged
+#![cfg_attr(staged, feature(staged))]
+
+#![feature(const_trait_impl)]
+#![allow(incomplete_features)]
+
+#![feature(staged_api)]
+#![stable(feature = "rust1", since = "1.0.0")]
+
+// aux-build: staged-api.rs
+extern crate staged_api;
+
+use staged_api::*;
+
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct Stable;
+
+#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(staged, rustc_const_stable(feature = "rust1", since = "1.0.0"))]
+// ^ should trigger error with or without the attribute
+impl const MyTrait for Stable {
+    fn func() { //~ ERROR trait methods cannot be stable const fn
+
+    }
+}
+
+fn non_const_context() {
+    Unstable::func();
+    Stable::func();
+}
+
+#[unstable(feature = "none", issue = "none")]
+const fn const_context() {
+    Unstable::func();
+    //[stock]~^ ERROR `<staged_api::Unstable as staged_api::MyTrait>::func` is not yet stable as a const fn
+    Stable::func();
+}
+
+fn main() {}

src/test/ui/rfc-2632-const-trait-impl/staged-api.staged.stderr

@@ -0,0 +1,10 @@
+error: trait methods cannot be stable const fn
+  --> $DIR/staged-api.rs:22:5
+   |
+LL | /     fn func() {
+LL | |
+LL | |     }
+   | |_____^
+
+error: aborting due to previous error
+

src/test/ui/rfc-2632-const-trait-impl/staged-api.stock.stderr

@@ -0,0 +1,18 @@
+error: trait methods cannot be stable const fn
+  --> $DIR/staged-api.rs:22:5
+   |
+LL | /     fn func() {
+LL | |
+LL | |     }
+   | |_____^
+
+error: `<staged_api::Unstable as staged_api::MyTrait>::func` is not yet stable as a const fn
+  --> $DIR/staged-api.rs:34:5
+   |
+LL |     Unstable::func();
+   |     ^^^^^^^^^^^^^^^^
+   |
+   = help: add `#![feature(staged)]` to the crate attributes to enable
+
+error: aborting due to 2 previous errors
+