const fn: Improve wording

src/librustc_mir/transform/qualify_min_const_fn.rs

@@ -326,7 +326,12 @@ fn check_terminator(
                     abi::Abi::Rust if tcx.is_min_const_fn(def_id) => {},
                     abi::Abi::Rust => return Err((
                         span,
-                        "can only call other `min_const_fn` within a `min_const_fn`".into(),
+                        format!(
+                            "can only call other `const fn` within a `const fn`, \
+                             but `{:?}` is not stable as `const fn`",
+                            func,
+                        )
+                        .into(),
                     )),
                     abi => return Err((
                         span,

src/test/ui/consts/min_const_fn/min_const_fn_libstd_stability.rs

@@ -12,14 +12,14 @@ const fn foo() -> u32 { 42 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 // can't call non-min_const_fn
-const fn bar() -> u32 { foo() } //~ ERROR can only call other `min_const_fn`
+const fn bar() -> u32 { foo() } //~ ERROR can only call other `const fn`
 
 #[unstable(feature = "rust1", issue="0")]
 const fn foo2() -> u32 { 42 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 // can't call non-min_const_fn
-const fn bar2() -> u32 { foo2() } //~ ERROR can only call other `min_const_fn`
+const fn bar2() -> u32 { foo2() } //~ ERROR can only call other `const fn`
 
 #[stable(feature = "rust1", since = "1.0.0")]
 // conformity is required, even with `const_fn` feature gate
@@ -31,6 +31,6 @@ const fn foo2_gated() -> u32 { 42 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 // can't call non-min_const_fn
-const fn bar2_gated() -> u32 { foo2_gated() } //~ ERROR can only call other `min_const_fn`
+const fn bar2_gated() -> u32 { foo2_gated() } //~ ERROR can only call other `const fn`
 
 fn main() {}

src/test/ui/consts/min_const_fn/min_const_fn_libstd_stability.stderr

@@ -1,12 +1,12 @@
-error[E0723]: can only call other `min_const_fn` within a `min_const_fn` (see issue #57563)
+error[E0723]: can only call other `const fn` within a `const fn`, but `const foo` is not stable as `const fn` (see issue #57563)
   --> $DIR/min_const_fn_libstd_stability.rs:15:25
    |
 LL | const fn bar() -> u32 { foo() }
    |                         ^^^^^
    |
    = help: add #![feature(const_fn)] to the crate attributes to enable
 
-error[E0723]: can only call other `min_const_fn` within a `min_const_fn` (see issue #57563)
+error[E0723]: can only call other `const fn` within a `const fn`, but `const foo2` is not stable as `const fn` (see issue #57563)
   --> $DIR/min_const_fn_libstd_stability.rs:22:26
    |
 LL | const fn bar2() -> u32 { foo2() }
@@ -22,7 +22,7 @@ LL | const fn bar3() -> u32 { (5f32 + 6f32) as u32 }
    |
    = help: add #![feature(const_fn)] to the crate attributes to enable
 
-error[E0723]: can only call other `min_const_fn` within a `min_const_fn` (see issue #57563)
+error[E0723]: can only call other `const fn` within a `const fn`, but `const foo2_gated` is not stable as `const fn` (see issue #57563)
   --> $DIR/min_const_fn_libstd_stability.rs:34:32
    |
 LL | const fn bar2_gated() -> u32 { foo2_gated() }

src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.rs

@@ -12,14 +12,14 @@ const unsafe fn foo() -> u32 { 42 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 // can't call non-min_const_fn
-const unsafe fn bar() -> u32 { unsafe { foo() } } //~ ERROR can only call other `min_const_fn`
+const unsafe fn bar() -> u32 { unsafe { foo() } } //~ ERROR can only call other `const fn`
 
 #[unstable(feature = "rust1", issue="0")]
 const unsafe fn foo2() -> u32 { 42 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 // can't call non-min_const_fn
-const unsafe fn bar2() -> u32 { unsafe { foo2() } } //~ ERROR can only call other `min_const_fn`
+const unsafe fn bar2() -> u32 { unsafe { foo2() } } //~ ERROR can only call other `const fn`
 
 #[stable(feature = "rust1", since = "1.0.0")]
 // conformity is required, even with `const_fn` feature gate
@@ -31,6 +31,7 @@ const unsafe fn foo2_gated() -> u32 { 42 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 // can't call non-min_const_fn
-const unsafe fn bar2_gated() -> u32 { unsafe { foo2_gated() } } //~ ERROR can only call other
+const unsafe fn bar2_gated() -> u32 { unsafe { foo2_gated() } }
+//~^ ERROR can only call other `const fn`
 
 fn main() {}

src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.stderr

@@ -1,12 +1,12 @@
-error[E0723]: can only call other `min_const_fn` within a `min_const_fn` (see issue #57563)
+error[E0723]: can only call other `const fn` within a `const fn`, but `const foo` is not stable as `const fn` (see issue #57563)
   --> $DIR/min_const_unsafe_fn_libstd_stability.rs:15:41
    |
 LL | const unsafe fn bar() -> u32 { unsafe { foo() } }
    |                                         ^^^^^
    |
    = help: add #![feature(const_fn)] to the crate attributes to enable
 
-error[E0723]: can only call other `min_const_fn` within a `min_const_fn` (see issue #57563)
+error[E0723]: can only call other `const fn` within a `const fn`, but `const foo2` is not stable as `const fn` (see issue #57563)
   --> $DIR/min_const_unsafe_fn_libstd_stability.rs:22:42
    |
 LL | const unsafe fn bar2() -> u32 { unsafe { foo2() } }
@@ -22,7 +22,7 @@ LL | const unsafe fn bar3() -> u32 { (5f32 + 6f32) as u32 }
    |
    = help: add #![feature(const_fn)] to the crate attributes to enable
 
-error[E0723]: can only call other `min_const_fn` within a `min_const_fn` (see issue #57563)
+error[E0723]: can only call other `const fn` within a `const fn`, but `const foo2_gated` is not stable as `const fn` (see issue #57563)
   --> $DIR/min_const_unsafe_fn_libstd_stability.rs:34:48
    |
 LL | const unsafe fn bar2_gated() -> u32 { unsafe { foo2_gated() } }

src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability2.rs

@@ -12,21 +12,21 @@ const fn foo() -> u32 { 42 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 // can't call non-min_const_fn
-const unsafe fn bar() -> u32 { foo() } //~ ERROR can only call other `min_const_fn`
+const unsafe fn bar() -> u32 { foo() } //~ ERROR can only call other `const fn`
 
 #[unstable(feature = "rust1", issue="0")]
 const fn foo2() -> u32 { 42 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 // can't call non-min_const_fn
-const unsafe fn bar2() -> u32 { foo2() } //~ ERROR can only call other `min_const_fn`
+const unsafe fn bar2() -> u32 { foo2() } //~ ERROR can only call other `const fn`
 
 // check whether this function cannot be called even with the feature gate active
 #[unstable(feature = "foo2", issue="0")]
 const fn foo2_gated() -> u32 { 42 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 // can't call non-min_const_fn
-const unsafe fn bar2_gated() -> u32 { foo2_gated() } //~ ERROR can only call other `min_const_fn`
+const unsafe fn bar2_gated() -> u32 { foo2_gated() } //~ ERROR can only call other `const fn`
 
 fn main() {}

src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability2.stderr

@@ -1,20 +1,20 @@
-error[E0723]: can only call other `min_const_fn` within a `min_const_fn` (see issue #57563)
+error[E0723]: can only call other `const fn` within a `const fn`, but `const foo` is not stable as `const fn` (see issue #57563)
   --> $DIR/min_const_unsafe_fn_libstd_stability2.rs:15:32
    |
 LL | const unsafe fn bar() -> u32 { foo() }
    |                                ^^^^^
    |
    = help: add #![feature(const_fn)] to the crate attributes to enable
 
-error[E0723]: can only call other `min_const_fn` within a `min_const_fn` (see issue #57563)
+error[E0723]: can only call other `const fn` within a `const fn`, but `const foo2` is not stable as `const fn` (see issue #57563)
   --> $DIR/min_const_unsafe_fn_libstd_stability2.rs:22:33
    |
 LL | const unsafe fn bar2() -> u32 { foo2() }
    |                                 ^^^^^^
    |
    = help: add #![feature(const_fn)] to the crate attributes to enable
 
-error[E0723]: can only call other `min_const_fn` within a `min_const_fn` (see issue #57563)
+error[E0723]: can only call other `const fn` within a `const fn`, but `const foo2_gated` is not stable as `const fn` (see issue #57563)
   --> $DIR/min_const_unsafe_fn_libstd_stability2.rs:30:39
    |
 LL | const unsafe fn bar2_gated() -> u32 { foo2_gated() }