Rollup merge of rust-lang#122440 - RalfJung:required-consts, r=oli-obk

const-eval: organize and extend tests for required-consts

This includes some tests that are known-broken and hence disabled (due to rust-lang#107503).

r? ``@oli-obk``

tests/ui/consts/required-consts/collect-in-called-fn.noopt.stderr

@@ -0,0 +1,17 @@
+error[E0080]: evaluation of `Fail::<i32>::C` failed
+  --> $DIR/collect-in-called-fn.rs:9:19
+   |
+LL |     const C: () = panic!();
+   |                   ^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/collect-in-called-fn.rs:9:19
+   |
+   = note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+note: the above error was encountered while instantiating `fn called::<i32>`
+  --> $DIR/collect-in-called-fn.rs:23:5
+   |
+LL |     called::<i32>();
+   |     ^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0080`.

tests/ui/consts/required-consts/collect-in-called-fn.opt.stderr

@@ -0,0 +1,17 @@
+error[E0080]: evaluation of `Fail::<i32>::C` failed
+  --> $DIR/collect-in-called-fn.rs:9:19
+   |
+LL |     const C: () = panic!();
+   |                   ^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/collect-in-called-fn.rs:9:19
+   |
+   = note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+note: the above error was encountered while instantiating `fn called::<i32>`
+  --> $DIR/collect-in-called-fn.rs:23:5
+   |
+LL |     called::<i32>();
+   |     ^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0080`.

tests/ui/consts/const-eval/unused-broken-const-late.rs → tests/ui/consts/required-consts/collect-in-called-fn.rs

@@ -1,20 +1,24 @@
+//@revisions: noopt opt
 //@ build-fail
-//@ compile-flags: -O
+//@[opt] compile-flags: -O
 //! Make sure we detect erroneous constants post-monomorphization even when they are unused. This is
 //! crucial, people rely on it for soundness. (https://github.com/rust-lang/rust/issues/112090)
 
-struct PrintName<T>(T);
-impl<T> PrintName<T> {
-    const VOID: () = panic!(); //~ERROR evaluation of `PrintName::<i32>::VOID` failed
+struct Fail<T>(T);
+impl<T> Fail<T> {
+    const C: () = panic!(); //~ERROR evaluation of `Fail::<i32>::C` failed
 }
 
-fn no_codegen<T>() {
+#[inline(never)]
+fn called<T>() {
     // Any function that is called is guaranteed to have all consts that syntactically
     // appear in its body evaluated, even if they only appear in dead code.
+    // This relies on mono-item collection checking `required_consts` in collected functions.
     if false {
-        let _ = PrintName::<T>::VOID;
+        let _ = Fail::<T>::C;
     }
 }
+
 pub fn main() {
-    no_codegen::<i32>();
+    called::<i32>();
 }

tests/ui/consts/required-consts/collect-in-dead-drop.noopt.stderr

@@ -0,0 +1,14 @@
+error[E0080]: evaluation of `Fail::<i32>::C` failed
+  --> $DIR/collect-in-dead-drop.rs:12:19
+   |
+LL |     const C: () = panic!();
+   |                   ^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/collect-in-dead-drop.rs:12:19
+   |
+   = note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+note: the above error was encountered while instantiating `fn <Fail<i32> as std::ops::Drop>::drop`
+  --> $SRC_DIR/core/src/ptr/mod.rs:LL:COL
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0080`.

tests/ui/consts/required-consts/collect-in-dead-drop.rs

@@ -0,0 +1,33 @@
+//@revisions: noopt opt
+//@[noopt] build-fail
+//@[opt] compile-flags: -O
+//FIXME: `opt` revision currently does not stop with an error due to
+//<https://github.com/rust-lang/rust/issues/107503>.
+//@[opt] build-pass
+//! Make sure we detect erroneous constants post-monomorphization even when they are unused. This is
+//! crucial, people rely on it for soundness. (https://github.com/rust-lang/rust/issues/112090)
+
+struct Fail<T>(T);
+impl<T> Fail<T> {
+    const C: () = panic!(); //[noopt]~ERROR evaluation of `Fail::<i32>::C` failed
+}
+
+// This function is not actually called, but is mentioned implicitly as destructor in dead code in a
+// function that is called. Make sure we still find this error.
+impl<T> Drop for Fail<T> {
+    fn drop(&mut self) {
+        let _ = Fail::<T>::C;
+    }
+}
+
+#[inline(never)]
+fn called<T>(x: T) {
+    if false {
+        let v = Fail(x);
+        // Now it gest dropped implicitly, at the end of this scope.
+    }
+}
+
+pub fn main() {
+    called::<i32>(0);
+}

tests/ui/consts/required-consts/collect-in-dead-fn.noopt.stderr

@@ -0,0 +1,17 @@
+error[E0080]: evaluation of `Fail::<i32>::C` failed
+  --> $DIR/collect-in-dead-fn.rs:12:19
+   |
+LL |     const C: () = panic!();
+   |                   ^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/collect-in-dead-fn.rs:12:19
+   |
+   = note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+note: the above error was encountered while instantiating `fn not_called::<i32>`
+  --> $DIR/collect-in-dead-fn.rs:29:9
+   |
+LL |         not_called::<T>();
+   |         ^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0080`.

tests/ui/consts/required-consts/collect-in-dead-fn.rs

@@ -0,0 +1,35 @@
+//@revisions: noopt opt
+//@[noopt] build-fail
+//@[opt] compile-flags: -O
+//FIXME: `opt` revision currently does not stop with an error due to
+//<https://github.com/rust-lang/rust/issues/107503>.
+//@[opt] build-pass
+//! Make sure we detect erroneous constants post-monomorphization even when they are unused. This is
+//! crucial, people rely on it for soundness. (https://github.com/rust-lang/rust/issues/112090)
+
+struct Fail<T>(T);
+impl<T> Fail<T> {
+    const C: () = panic!(); //[noopt]~ERROR evaluation of `Fail::<i32>::C` failed
+}
+
+// This function is not actually called, but it is mentioned in dead code in a function that is
+// called. Make sure we still find this error.
+// This relies on mono-item collection checking `required_consts` in functions that syntactically
+// are called in collected functions (even inside dead code).
+#[inline(never)]
+fn not_called<T>() {
+    if false {
+        let _ = Fail::<T>::C;
+    }
+}
+
+#[inline(never)]
+fn called<T>() {
+    if false {
+        not_called::<T>();
+    }
+}
+
+pub fn main() {
+    called::<i32>();
+}

tests/ui/consts/required-consts/collect-in-dead-forget.rs

@@ -0,0 +1,32 @@
+//@revisions: noopt opt
+//@build-pass
+//@[opt] compile-flags: -O
+//! Make sure we detect erroneous constants post-monomorphization even when they are unused. This is
+//! crucial, people rely on it for soundness. (https://github.com/rust-lang/rust/issues/112090)
+
+struct Fail<T>(T);
+impl<T> Fail<T> {
+    const C: () = panic!();
+}
+
+// This function is not actually called, but is mentioned implicitly as destructor in dead code in a
+// function that is called. Make sure we still find this error.
+impl<T> Drop for Fail<T> {
+    fn drop(&mut self) {
+        let _ = Fail::<T>::C;
+    }
+}
+
+#[inline(never)]
+fn called<T>(x: T) {
+    if false {
+        let v = Fail(x);
+        std::mem::forget(v);
+        // Now the destructor never gets "mentioned" so this build should *not* fail.
+        // IOW, this demonstrates that we are using a post-drop-elab notion of "mentioned".
+    }
+}
+
+pub fn main() {
+    called::<i32>(0);
+}

tests/ui/consts/required-consts/collect-in-dead-move.noopt.stderr

@@ -0,0 +1,14 @@
+error[E0080]: evaluation of `Fail::<i32>::C` failed
+  --> $DIR/collect-in-dead-move.rs:12:19
+   |
+LL |     const C: () = panic!();
+   |                   ^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/collect-in-dead-move.rs:12:19
+   |
+   = note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+note: the above error was encountered while instantiating `fn <Fail<i32> as std::ops::Drop>::drop`
+  --> $SRC_DIR/core/src/ptr/mod.rs:LL:COL
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0080`.

tests/ui/consts/required-consts/collect-in-dead-move.rs

@@ -0,0 +1,33 @@
+//@revisions: noopt opt
+//@[noopt] build-fail
+//@[opt] compile-flags: -O
+//FIXME: `opt` revision currently does not stop with an error due to
+//<https://github.com/rust-lang/rust/issues/107503>.
+//@[opt] build-pass
+//! Make sure we detect erroneous constants post-monomorphization even when they are unused. This is
+//! crucial, people rely on it for soundness. (https://github.com/rust-lang/rust/issues/112090)
+
+struct Fail<T>(T);
+impl<T> Fail<T> {
+    const C: () = panic!(); //[noopt]~ERROR evaluation of `Fail::<i32>::C` failed
+}
+
+// This function is not actually called, but is mentioned implicitly as destructor in dead code in a
+// function that is called. Make sure we still find this error.
+impl<T> Drop for Fail<T> {
+    fn drop(&mut self) {
+        let _ = Fail::<T>::C;
+    }
+}
+
+#[inline(never)]
+fn called<T>(x: T) {
+    if false {
+        let v = Fail(x);
+        drop(v); // move `v` away (and it then gets dropped there so build still fails)
+    }
+}
+
+pub fn main() {
+    called::<i32>(0);
+}

tests/ui/consts/required-consts/collect-in-dead-vtable.noopt.stderr

@@ -0,0 +1,17 @@
+error[E0080]: evaluation of `Fail::<i32>::C` failed
+  --> $DIR/collect-in-dead-vtable.rs:12:19
+   |
+LL |     const C: () = panic!();
+   |                   ^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/collect-in-dead-vtable.rs:12:19
+   |
+   = note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+note: the above error was encountered while instantiating `fn <std::vec::Vec<i32> as MyTrait>::not_called`
+  --> $DIR/collect-in-dead-vtable.rs:35:40
+   |
+LL |         let gen_vtable: &dyn MyTrait = &v; // vtable "appears" here
+   |                                        ^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0080`.

tests/ui/consts/required-consts/collect-in-dead-vtable.rs

@@ -0,0 +1,41 @@
+//@revisions: noopt opt
+//@[noopt] build-fail
+//@[opt] compile-flags: -O
+//FIXME: `opt` revision currently does not stop with an error due to
+//<https://github.com/rust-lang/rust/issues/107503>.
+//@[opt] build-pass
+//! Make sure we detect erroneous constants post-monomorphization even when they are unused. This is
+//! crucial, people rely on it for soundness. (https://github.com/rust-lang/rust/issues/112090)
+
+struct Fail<T>(T);
+impl<T> Fail<T> {
+    const C: () = panic!(); //[noopt]~ERROR evaluation of `Fail::<i32>::C` failed
+}
+
+trait MyTrait {
+    fn not_called(&self);
+}
+
+// This function is not actually called, but it is mentioned in a vtable in a function that is
+// called. Make sure we still find this error.
+// This relies on mono-item collection checking `required_consts` in functions that are referenced
+// in vtables that syntactically appear in collected functions (even inside dead code).
+impl<T> MyTrait for Vec<T> {
+    fn not_called(&self) {
+        if false {
+            let _ = Fail::<T>::C;
+        }
+    }
+}
+
+#[inline(never)]
+fn called<T>() {
+    if false {
+        let v: Vec<T> = Vec::new();
+        let gen_vtable: &dyn MyTrait = &v; // vtable "appears" here
+    }
+}
+
+pub fn main() {
+    called::<i32>();
+}

tests/ui/consts/required-consts/interpret-in-const-called-fn.noopt.stderr

@@ -0,0 +1,17 @@
+error[E0080]: evaluation of `Fail::<i32>::C` failed
+  --> $DIR/interpret-in-const-called-fn.rs:7:19
+   |
+LL |     const C: () = panic!();
+   |                   ^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/interpret-in-const-called-fn.rs:7:19
+   |
+   = note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+note: erroneous constant encountered
+  --> $DIR/interpret-in-const-called-fn.rs:16:9
+   |
+LL |         Fail::<T>::C;
+   |         ^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0080`.