fn must be const if marked with stability attribut

remove trailing newline

fix: test with attribute but missing const

Update compiler/rustc_passes/src/stability.rs

Co-authored-by: Léo Lanteri Thauvin <leseulartichaut@gmail.com>

Add test for extern functions

fix: using span_help instead of span_suggestion

add test for some ABIs + fmt fix

Update compiler/rustc_passes/src/stability.rs

Co-authored-by: Léo Lanteri Thauvin <leseulartichaut@gmail.com>

Refractor and add test for `impl const`

Add test to make sure no output + cleanup condition

-----------------------------

remove stdcall test, failing CI test

C abi is already tested in this, so it is not that useful to test another one.
The tested code is blind to which specific ABI for now, as long as it's not an intrinsic one

compiler/rustc_error_codes/src/error_codes/E0542.md

@@ -10,7 +10,7 @@ Erroneous code example:
 fn _stable_fn() {}
 
 #[rustc_const_stable(feature = "_stable_const_fn")] // invalid
-fn _stable_const_fn() {}
+const fn _stable_const_fn() {}
 
 #[stable(feature = "_deprecated_fn", since = "0.1.0")]
 #[rustc_deprecated(
@@ -29,7 +29,7 @@ To fix this issue, you need to provide the `since` field. Example:
 fn _stable_fn() {}
 
 #[rustc_const_stable(feature = "_stable_const_fn", since = "1.0.0")] // ok!
-fn _stable_const_fn() {}
+const fn _stable_const_fn() {}
 
 #[stable(feature = "_deprecated_fn", since = "0.1.0")]
 #[rustc_deprecated(

compiler/rustc_error_codes/src/error_codes/E0545.md

@@ -10,7 +10,7 @@ Erroneous code example:
 fn _unstable_fn() {}
 
 #[rustc_const_unstable(feature = "_unstable_const_fn", issue = "0")] // invalid
-fn _unstable_const_fn() {}
+const fn _unstable_const_fn() {}
 ```
 
 To fix this issue, you need to provide a correct value in the `issue` field.
@@ -24,7 +24,7 @@ Example:
 fn _unstable_fn() {}
 
 #[rustc_const_unstable(feature = "_unstable_const_fn", issue = "1")] // ok!
-fn _unstable_const_fn() {}
+const fn _unstable_const_fn() {}
 ```
 
 See the [How Rust is Made and “Nightly Rust”][how-rust-made-nightly] appendix

compiler/rustc_error_codes/src/error_codes/E0547.md

@@ -10,7 +10,7 @@ Erroneous code example:
 fn _unstable_fn() {}
 
 #[rustc_const_unstable(feature = "_unstable_const_fn")] // invalid
-fn _unstable_const_fn() {}
+const fn _unstable_const_fn() {}
 ```
 
 To fix this issue, you need to provide the `issue` field. Example:
@@ -26,7 +26,7 @@ fn _unstable_fn() {}
     feature = "_unstable_const_fn",
     issue = "none"
 )] // ok!
-fn _unstable_const_fn() {}
+const fn _unstable_const_fn() {}
 ```
 
 See the [How Rust is Made and “Nightly Rust”][how-rust-made-nightly] appendix