Rollup merge of #88954 - nbdd0121:panic3, r=oli-obk

Allow `panic!("{}", computed_str)` in const fn.

Special-case `panic!("{}", arg)` and translate it to `panic_display(&arg)`. `panic_display` will behave like `panic_any` in cosnt eval and behave like `panic!(format_args!("{}", arg))` in runtime.

This should bring Rust 2015 and 2021 to feature parity in terms of `const_panic`; and hopefully would unblock the stabilisation of #51999.

`@rustbot` modify labels: +T-compiler +T-libs +A-const-eval +A-const-fn

r? `@oli-obk`

4 files changed, 83 insertions, 37 deletions

diff --git a/src/test/ui/consts/const-eval/const_panic.rs b/src/test/ui/consts/const-eval/const_panic.rs
index e4455d86a14..100faded079 100644
--- a/src/test/ui/consts/const-eval/const_panic.rs
+++ b/src/test/ui/consts/const-eval/const_panic.rs
@@ -15,10 +15,13 @@ const Y: () = std::unreachable!();
 
 const X: () = std::unimplemented!();
 //~^ ERROR evaluation of constant value failed
-//
+
 const W: () = std::panic!(MSG);
 //~^ ERROR evaluation of constant value failed
 
+const W2: () = std::panic!("{}", MSG);
+//~^ ERROR evaluation of constant value failed
+
 const Z_CORE: () = core::panic!("cheese");
 //~^ ERROR evaluation of constant value failed
 
@@ -33,3 +36,6 @@ const X_CORE: () = core::unimplemented!();
 
 const W_CORE: () = core::panic!(MSG);
 //~^ ERROR evaluation of constant value failed
+
+const W2_CORE: () = core::panic!("{}", MSG);
+//~^ ERROR evaluation of constant value failed
diff --git a/src/test/ui/consts/const-eval/const_panic.stderr b/src/test/ui/consts/const-eval/const_panic.stderr
index c0c749ede56..e98e4a506c0 100644
--- a/src/test/ui/consts/const-eval/const_panic.stderr
+++ b/src/test/ui/consts/const-eval/const_panic.stderr
@@ -39,45 +39,61 @@ LL | const W: () = std::panic!(MSG);
    = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0080]: evaluation of constant value failed
-  --> $DIR/const_panic.rs:22:20
+  --> $DIR/const_panic.rs:22:16
+   |
+LL | const W2: () = std::panic!("{}", MSG);
+   |                ^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'hello', $DIR/const_panic.rs:22:16
+   |
+   = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0080]: evaluation of constant value failed
+  --> $DIR/const_panic.rs:25:20
    |
 LL | const Z_CORE: () = core::panic!("cheese");
-   |                    ^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'cheese', $DIR/const_panic.rs:22:20
+   |                    ^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'cheese', $DIR/const_panic.rs:25:20
    |
    = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0080]: evaluation of constant value failed
-  --> $DIR/const_panic.rs:25:21
+  --> $DIR/const_panic.rs:28:21
    |
 LL | const Z2_CORE: () = core::panic!();
-   |                     ^^^^^^^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/const_panic.rs:25:21
+   |                     ^^^^^^^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/const_panic.rs:28:21
    |
    = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0080]: evaluation of constant value failed
-  --> $DIR/const_panic.rs:28:20
+  --> $DIR/const_panic.rs:31:20
    |
 LL | const Y_CORE: () = core::unreachable!();
-   |                    ^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'internal error: entered unreachable code', $DIR/const_panic.rs:28:20
+   |                    ^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'internal error: entered unreachable code', $DIR/const_panic.rs:31:20
    |
    = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0080]: evaluation of constant value failed
-  --> $DIR/const_panic.rs:31:20
+  --> $DIR/const_panic.rs:34:20
    |
 LL | const X_CORE: () = core::unimplemented!();
-   |                    ^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'not implemented', $DIR/const_panic.rs:31:20
+   |                    ^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'not implemented', $DIR/const_panic.rs:34:20
    |
    = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0080]: evaluation of constant value failed
-  --> $DIR/const_panic.rs:34:20
+  --> $DIR/const_panic.rs:37:20
    |
 LL | const W_CORE: () = core::panic!(MSG);
-   |                    ^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'hello', $DIR/const_panic.rs:34:20
+   |                    ^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'hello', $DIR/const_panic.rs:37:20
+   |
+   = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0080]: evaluation of constant value failed
+  --> $DIR/const_panic.rs:40:21
+   |
+LL | const W2_CORE: () = core::panic!("{}", MSG);
+   |                     ^^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'hello', $DIR/const_panic.rs:40:21
    |
    = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: aborting due to 10 previous errors
+error: aborting due to 12 previous errors
 
 For more information about this error, try `rustc --explain E0080`.
diff --git a/src/test/ui/consts/const-eval/const_panic_2021.rs b/src/test/ui/consts/const-eval/const_panic_2021.rs
index daef34cd6a3..9b8652a776e 100644
--- a/src/test/ui/consts/const-eval/const_panic_2021.rs
+++ b/src/test/ui/consts/const-eval/const_panic_2021.rs
@@ -2,6 +2,8 @@
 #![feature(const_panic)]
 #![crate_type = "lib"]
 
+const MSG: &str = "hello";
+
 const A: () = std::panic!("blåhaj");
 //~^ ERROR evaluation of constant value failed
 
@@ -14,14 +16,20 @@ const C: () = std::unreachable!();
 const D: () = std::unimplemented!();
 //~^ ERROR evaluation of constant value failed
 
-const E: () = core::panic!("shark");
+const E: () = std::panic!("{}", MSG);
+//~^ ERROR evaluation of constant value failed
+
+const A_CORE: () = core::panic!("shark");
+//~^ ERROR evaluation of constant value failed
+
+const B_CORE: () = core::panic!();
 //~^ ERROR evaluation of constant value failed
 
-const F: () = core::panic!();
+const C_CORE: () = core::unreachable!();
 //~^ ERROR evaluation of constant value failed
 
-const G: () = core::unreachable!();
+const D_CORE: () = core::unimplemented!();
 //~^ ERROR evaluation of constant value failed
 
-const H: () = core::unimplemented!();
+const E_CORE: () = core::panic!("{}", MSG);
 //~^ ERROR evaluation of constant value failed
diff --git a/src/test/ui/consts/const-eval/const_panic_2021.stderr b/src/test/ui/consts/const-eval/const_panic_2021.stderr
index c1bdab3693d..9eb241ae8e5 100644
--- a/src/test/ui/consts/const-eval/const_panic_2021.stderr
+++ b/src/test/ui/consts/const-eval/const_panic_2021.stderr
@@ -1,67 +1,83 @@
 error[E0080]: evaluation of constant value failed
-  --> $DIR/const_panic_2021.rs:5:15
+  --> $DIR/const_panic_2021.rs:7:15
    |
 LL | const A: () = std::panic!("blåhaj");
-   |               ^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'blåhaj', $DIR/const_panic_2021.rs:5:15
+   |               ^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'blåhaj', $DIR/const_panic_2021.rs:7:15
    |
    = note: this error originates in the macro `$crate::panic::panic_2021` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0080]: evaluation of constant value failed
-  --> $DIR/const_panic_2021.rs:8:15
+  --> $DIR/const_panic_2021.rs:10:15
    |
 LL | const B: () = std::panic!();
-   |               ^^^^^^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/const_panic_2021.rs:8:15
+   |               ^^^^^^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/const_panic_2021.rs:10:15
    |
    = note: this error originates in the macro `$crate::panic::panic_2021` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0080]: evaluation of constant value failed
-  --> $DIR/const_panic_2021.rs:11:15
+  --> $DIR/const_panic_2021.rs:13:15
    |
 LL | const C: () = std::unreachable!();
-   |               ^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'internal error: entered unreachable code', $DIR/const_panic_2021.rs:11:15
+   |               ^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'internal error: entered unreachable code', $DIR/const_panic_2021.rs:13:15
    |
    = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0080]: evaluation of constant value failed
-  --> $DIR/const_panic_2021.rs:14:15
+  --> $DIR/const_panic_2021.rs:16:15
    |
 LL | const D: () = std::unimplemented!();
-   |               ^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'not implemented', $DIR/const_panic_2021.rs:14:15
+   |               ^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'not implemented', $DIR/const_panic_2021.rs:16:15
    |
    = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0080]: evaluation of constant value failed
-  --> $DIR/const_panic_2021.rs:17:15
+  --> $DIR/const_panic_2021.rs:19:15
    |
-LL | const E: () = core::panic!("shark");
-   |               ^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'shark', $DIR/const_panic_2021.rs:17:15
+LL | const E: () = std::panic!("{}", MSG);
+   |               ^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'hello', $DIR/const_panic_2021.rs:19:15
    |
    = note: this error originates in the macro `$crate::panic::panic_2021` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0080]: evaluation of constant value failed
-  --> $DIR/const_panic_2021.rs:20:15
+  --> $DIR/const_panic_2021.rs:22:20
    |
-LL | const F: () = core::panic!();
-   |               ^^^^^^^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/const_panic_2021.rs:20:15
+LL | const A_CORE: () = core::panic!("shark");
+   |                    ^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'shark', $DIR/const_panic_2021.rs:22:20
    |
    = note: this error originates in the macro `$crate::panic::panic_2021` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0080]: evaluation of constant value failed
-  --> $DIR/const_panic_2021.rs:23:15
+  --> $DIR/const_panic_2021.rs:25:20
    |
-LL | const G: () = core::unreachable!();
-   |               ^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'internal error: entered unreachable code', $DIR/const_panic_2021.rs:23:15
+LL | const B_CORE: () = core::panic!();
+   |                    ^^^^^^^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/const_panic_2021.rs:25:20
+   |
+   = note: this error originates in the macro `$crate::panic::panic_2021` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0080]: evaluation of constant value failed
+  --> $DIR/const_panic_2021.rs:28:20
+   |
+LL | const C_CORE: () = core::unreachable!();
+   |                    ^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'internal error: entered unreachable code', $DIR/const_panic_2021.rs:28:20
    |
    = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0080]: evaluation of constant value failed
-  --> $DIR/const_panic_2021.rs:26:15
+  --> $DIR/const_panic_2021.rs:31:20
    |
-LL | const H: () = core::unimplemented!();
-   |               ^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'not implemented', $DIR/const_panic_2021.rs:26:15
+LL | const D_CORE: () = core::unimplemented!();
+   |                    ^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'not implemented', $DIR/const_panic_2021.rs:31:20
    |
    = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: aborting due to 8 previous errors
+error[E0080]: evaluation of constant value failed
+  --> $DIR/const_panic_2021.rs:34:20
+   |
+LL | const E_CORE: () = core::panic!("{}", MSG);
+   |                    ^^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'hello', $DIR/const_panic_2021.rs:34:20
+   |
+   = note: this error originates in the macro `$crate::panic::panic_2021` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 10 previous errors
 
 For more information about this error, try `rustc --explain E0080`.