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

Author: RalfJung

tests/ui/consts/const-eval/erroneous-const.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/erroneous-const2.rs

@@ -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/erroneous-const2.stderr

@@ -1,20 +1,24 @@
+//@revisions: opt no-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/const-eval/unused-broken-const-late.stderr

@@ -0,0 +1,14 @@
+error[E0080]: evaluation of `Fail::<i32>::C` failed
+  --> $DIR/collect-in-dead-drop.rs:11:19
+   |
+LL |     const C: () = panic!();
+   |                   ^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/collect-in-dead-drop.rs:11:19
+   |
+   = note: this error originates in the macro `$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-called-fn.no-opt.stderr

@@ -0,0 +1,32 @@
+//@revisions: no-opt
+//FIXME: `opt` revision currently does not stop with an error due to
+//<https://github.com/rust-lang/rust/issues/107503>.
+//@ build-fail
+//@[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!(); //~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);
+    }
+}
+
+pub fn main() {
+    called::<i32>(0);
+}

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-dead-fn.rs:11:19
+   |
+LL |     const C: () = panic!();
+   |                   ^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/collect-in-dead-fn.rs:11:19
+   |
+   = note: this error originates in the macro `$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:28:9
+   |
+LL |         not_called::<T>();
+   |         ^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0080`.