Rollup merge of #98276 - compiler-errors:const-format-macro, r=oli-obk

Mention formatting macros when encountering `ArgumentV1` method in const

Also open to just closing this if it's overkill. There are a lot of other distracting error messages around, so maybe it's not worth fixing just this one.

Fixes #93665

src/test/ui/consts/const-eval/format.rs

@@ -0,0 +1,21 @@
+const fn failure() {
+    panic!("{:?}", 0);
+    //~^ ERROR cannot call non-const formatting macro in constant functions
+    //~| ERROR erroneous constant used
+    //~| ERROR erroneous constant used
+    //~| WARN this was previously accepted by the compiler
+    //~| WARN this was previously accepted by the compiler
+}
+
+const fn print() {
+    println!("{:?}", 0);
+    //~^ ERROR cannot call non-const formatting macro in constant functions
+    //~| ERROR `Arguments::<'a>::new_v1` is not yet stable as a const fn
+    //~| ERROR cannot call non-const fn `_print` in constant functions
+    //~| ERROR erroneous constant used
+    //~| ERROR erroneous constant used
+    //~| WARN this was previously accepted by the compiler
+    //~| WARN this was previously accepted by the compiler
+}
+
+fn main() {}

src/test/ui/consts/const-eval/format.stderr

@@ -0,0 +1,78 @@
+error[E0015]: cannot call non-const formatting macro in constant functions
+  --> $DIR/format.rs:2:20
+   |
+LL |     panic!("{:?}", 0);
+   |                    ^
+   |
+   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
+   = note: this error originates in the macro `$crate::const_format_args` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0015]: cannot call non-const formatting macro in constant functions
+  --> $DIR/format.rs:11:22
+   |
+LL |     println!("{:?}", 0);
+   |                      ^
+   |
+   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
+   = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: `Arguments::<'a>::new_v1` is not yet stable as a const fn
+  --> $DIR/format.rs:11:5
+   |
+LL |     println!("{:?}", 0);
+   |     ^^^^^^^^^^^^^^^^^^^
+   |
+   = help: add `#![feature(const_fmt_arguments_new)]` to the crate attributes to enable
+   = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0015]: cannot call non-const fn `_print` in constant functions
+  --> $DIR/format.rs:11:5
+   |
+LL |     println!("{:?}", 0);
+   |     ^^^^^^^^^^^^^^^^^^^
+   |
+   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
+   = note: this error originates in the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: erroneous constant used
+  --> $DIR/format.rs:2:12
+   |
+LL |     panic!("{:?}", 0);
+   |            ^^^^^^ referenced constant has errors
+   |
+   = note: `#[deny(const_err)]` on by default
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
+
+error: erroneous constant used
+  --> $DIR/format.rs:2:20
+   |
+LL |     panic!("{:?}", 0);
+   |                    ^ referenced constant has errors
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
+   = note: this error originates in the macro `$crate::const_format_args` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: erroneous constant used
+  --> $DIR/format.rs:11:14
+   |
+LL |     println!("{:?}", 0);
+   |              ^^^^^^ referenced constant has errors
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
+
+error: erroneous constant used
+  --> $DIR/format.rs:11:22
+   |
+LL |     println!("{:?}", 0);
+   |                      ^ referenced constant has errors
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
+   = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 8 previous errors
+
+For more information about this error, try `rustc --explain E0015`.