Add test for extern without explicit ABI

tests/ui/feature-gates/feature-gate-explicit-extern-abis.current.fixed

@@ -0,0 +1,45 @@
+// The purpose of this feature gate is to make something into a hard error in a
+// future edition.  Consequently, this test differs from most other feature gate
+// tests.  Instead of verifying that an error occurs when the feature gate is
+// missing, it ensures that the hard error is only produced with the feature
+// gate is present in the `future` edition -- and otherwise that only a warning
+// is emitted.
+
+//@ revisions: current current_feature future future_feature
+
+//@ [current] run-rustfix
+//@ [current] check-pass
+
+//@ [current_feature] run-rustfix
+//@ [current_feature] check-pass
+
+//@ [future] edition: future
+//@ [future] compile-flags: -Z unstable-options
+//@ [future] run-rustfix
+//@ [future] check-pass
+
+//@ [future_feature] edition: future
+//@ [future_feature] compile-flags: -Z unstable-options
+
+#![cfg_attr(future_feature, feature(explicit_extern_abis))]
+#![cfg_attr(current_feature, feature(explicit_extern_abis))]
+
+extern "C" fn _foo() {}
+//[current]~^ WARN `extern` declarations without an explicit ABI are deprecated
+//[current_feature]~^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future]~^^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future_feature]~^^^^ ERROR `extern` declarations without an explicit ABI are disallowed
+
+unsafe extern "C" fn _bar() {}
+//[current]~^ WARN `extern` declarations without an explicit ABI are deprecated
+//[current_feature]~^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future]~^^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future_feature]~^^^^ ERROR `extern` declarations without an explicit ABI are disallowed
+
+unsafe extern "C" {}
+//[current]~^ WARN `extern` declarations without an explicit ABI are deprecated
+//[current_feature]~^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future]~^^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future_feature]~^^^^ ERROR `extern` declarations without an explicit ABI are disallowed
+
+fn main() {}

tests/ui/feature-gates/feature-gate-explicit-extern-abis.current.stderr

@@ -0,0 +1,22 @@
+warning: `extern` declarations without an explicit ABI are deprecated
+  --> $DIR/feature-gate-explicit-extern-abis.rs:27:1
+   |
+LL | extern fn _foo() {}
+   | ^^^^^^ help: explicitly specify the "C" ABI: `extern "C"`
+   |
+   = note: `#[warn(missing_abi)]` on by default
+
+warning: `extern` declarations without an explicit ABI are deprecated
+  --> $DIR/feature-gate-explicit-extern-abis.rs:33:8
+   |
+LL | unsafe extern fn _bar() {}
+   |        ^^^^^^ help: explicitly specify the "C" ABI: `extern "C"`
+
+warning: `extern` declarations without an explicit ABI are deprecated
+  --> $DIR/feature-gate-explicit-extern-abis.rs:39:8
+   |
+LL | unsafe extern {}
+   |        ^^^^^^ help: explicitly specify the "C" ABI: `extern "C"`
+
+warning: 3 warnings emitted
+

tests/ui/feature-gates/feature-gate-explicit-extern-abis.current_feature.fixed

@@ -0,0 +1,45 @@
+// The purpose of this feature gate is to make something into a hard error in a
+// future edition.  Consequently, this test differs from most other feature gate
+// tests.  Instead of verifying that an error occurs when the feature gate is
+// missing, it ensures that the hard error is only produced with the feature
+// gate is present in the `future` edition -- and otherwise that only a warning
+// is emitted.
+
+//@ revisions: current current_feature future future_feature
+
+//@ [current] run-rustfix
+//@ [current] check-pass
+
+//@ [current_feature] run-rustfix
+//@ [current_feature] check-pass
+
+//@ [future] edition: future
+//@ [future] compile-flags: -Z unstable-options
+//@ [future] run-rustfix
+//@ [future] check-pass
+
+//@ [future_feature] edition: future
+//@ [future_feature] compile-flags: -Z unstable-options
+
+#![cfg_attr(future_feature, feature(explicit_extern_abis))]
+#![cfg_attr(current_feature, feature(explicit_extern_abis))]
+
+extern "C" fn _foo() {}
+//[current]~^ WARN `extern` declarations without an explicit ABI are deprecated
+//[current_feature]~^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future]~^^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future_feature]~^^^^ ERROR `extern` declarations without an explicit ABI are disallowed
+
+unsafe extern "C" fn _bar() {}
+//[current]~^ WARN `extern` declarations without an explicit ABI are deprecated
+//[current_feature]~^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future]~^^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future_feature]~^^^^ ERROR `extern` declarations without an explicit ABI are disallowed
+
+unsafe extern "C" {}
+//[current]~^ WARN `extern` declarations without an explicit ABI are deprecated
+//[current_feature]~^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future]~^^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future_feature]~^^^^ ERROR `extern` declarations without an explicit ABI are disallowed
+
+fn main() {}

tests/ui/feature-gates/feature-gate-explicit-extern-abis.current_feature.stderr

@@ -0,0 +1,22 @@
+warning: `extern` declarations without an explicit ABI are deprecated
+  --> $DIR/feature-gate-explicit-extern-abis.rs:27:1
+   |
+LL | extern fn _foo() {}
+   | ^^^^^^ help: explicitly specify the "C" ABI: `extern "C"`
+   |
+   = note: `#[warn(missing_abi)]` on by default
+
+warning: `extern` declarations without an explicit ABI are deprecated
+  --> $DIR/feature-gate-explicit-extern-abis.rs:33:8
+   |
+LL | unsafe extern fn _bar() {}
+   |        ^^^^^^ help: explicitly specify the "C" ABI: `extern "C"`
+
+warning: `extern` declarations without an explicit ABI are deprecated
+  --> $DIR/feature-gate-explicit-extern-abis.rs:39:8
+   |
+LL | unsafe extern {}
+   |        ^^^^^^ help: explicitly specify the "C" ABI: `extern "C"`
+
+warning: 3 warnings emitted
+

tests/ui/feature-gates/feature-gate-explicit-extern-abis.future.fixed

@@ -0,0 +1,45 @@
+// The purpose of this feature gate is to make something into a hard error in a
+// future edition.  Consequently, this test differs from most other feature gate
+// tests.  Instead of verifying that an error occurs when the feature gate is
+// missing, it ensures that the hard error is only produced with the feature
+// gate is present in the `future` edition -- and otherwise that only a warning
+// is emitted.
+
+//@ revisions: current current_feature future future_feature
+
+//@ [current] run-rustfix
+//@ [current] check-pass
+
+//@ [current_feature] run-rustfix
+//@ [current_feature] check-pass
+
+//@ [future] edition: future
+//@ [future] compile-flags: -Z unstable-options
+//@ [future] run-rustfix
+//@ [future] check-pass
+
+//@ [future_feature] edition: future
+//@ [future_feature] compile-flags: -Z unstable-options
+
+#![cfg_attr(future_feature, feature(explicit_extern_abis))]
+#![cfg_attr(current_feature, feature(explicit_extern_abis))]
+
+extern "C" fn _foo() {}
+//[current]~^ WARN `extern` declarations without an explicit ABI are deprecated
+//[current_feature]~^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future]~^^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future_feature]~^^^^ ERROR `extern` declarations without an explicit ABI are disallowed
+
+unsafe extern "C" fn _bar() {}
+//[current]~^ WARN `extern` declarations without an explicit ABI are deprecated
+//[current_feature]~^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future]~^^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future_feature]~^^^^ ERROR `extern` declarations without an explicit ABI are disallowed
+
+unsafe extern "C" {}
+//[current]~^ WARN `extern` declarations without an explicit ABI are deprecated
+//[current_feature]~^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future]~^^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future_feature]~^^^^ ERROR `extern` declarations without an explicit ABI are disallowed
+
+fn main() {}

tests/ui/feature-gates/feature-gate-explicit-extern-abis.future.stderr

@@ -0,0 +1,22 @@
+warning: `extern` declarations without an explicit ABI are deprecated
+  --> $DIR/feature-gate-explicit-extern-abis.rs:27:1
+   |
+LL | extern fn _foo() {}
+   | ^^^^^^ help: explicitly specify the "C" ABI: `extern "C"`
+   |
+   = note: `#[warn(missing_abi)]` on by default
+
+warning: `extern` declarations without an explicit ABI are deprecated
+  --> $DIR/feature-gate-explicit-extern-abis.rs:33:8
+   |
+LL | unsafe extern fn _bar() {}
+   |        ^^^^^^ help: explicitly specify the "C" ABI: `extern "C"`
+
+warning: `extern` declarations without an explicit ABI are deprecated
+  --> $DIR/feature-gate-explicit-extern-abis.rs:39:8
+   |
+LL | unsafe extern {}
+   |        ^^^^^^ help: explicitly specify the "C" ABI: `extern "C"`
+
+warning: 3 warnings emitted
+

tests/ui/feature-gates/feature-gate-explicit-extern-abis.future_feature.stderr

@@ -0,0 +1,26 @@
+error: `extern` declarations without an explicit ABI are disallowed
+  --> $DIR/feature-gate-explicit-extern-abis.rs:27:1
+   |
+LL | extern fn _foo() {}
+   | ^^^^^^ help: specify an ABI: `extern "<abi>"`
+   |
+   = help: prior to Rust 2024, a default ABI was inferred
+
+error: `extern` declarations without an explicit ABI are disallowed
+  --> $DIR/feature-gate-explicit-extern-abis.rs:33:8
+   |
+LL | unsafe extern fn _bar() {}
+   |        ^^^^^^ help: specify an ABI: `extern "<abi>"`
+   |
+   = help: prior to Rust 2024, a default ABI was inferred
+
+error: `extern` declarations without an explicit ABI are disallowed
+  --> $DIR/feature-gate-explicit-extern-abis.rs:39:8
+   |
+LL | unsafe extern {}
+   |        ^^^^^^ help: specify an ABI: `extern "<abi>"`
+   |
+   = help: prior to Rust 2024, a default ABI was inferred
+
+error: aborting due to 3 previous errors
+

tests/ui/feature-gates/feature-gate-explicit-extern-abis.rs

@@ -0,0 +1,45 @@
+// The purpose of this feature gate is to make something into a hard error in a
+// future edition.  Consequently, this test differs from most other feature gate
+// tests.  Instead of verifying that an error occurs when the feature gate is
+// missing, it ensures that the hard error is only produced with the feature
+// gate is present in the `future` edition -- and otherwise that only a warning
+// is emitted.
+
+//@ revisions: current current_feature future future_feature
+
+//@ [current] run-rustfix
+//@ [current] check-pass
+
+//@ [current_feature] run-rustfix
+//@ [current_feature] check-pass
+
+//@ [future] edition: future
+//@ [future] compile-flags: -Z unstable-options
+//@ [future] run-rustfix
+//@ [future] check-pass
+
+//@ [future_feature] edition: future
+//@ [future_feature] compile-flags: -Z unstable-options
+
+#![cfg_attr(future_feature, feature(explicit_extern_abis))]
+#![cfg_attr(current_feature, feature(explicit_extern_abis))]
+
+extern fn _foo() {}
+//[current]~^ WARN `extern` declarations without an explicit ABI are deprecated
+//[current_feature]~^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future]~^^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future_feature]~^^^^ ERROR `extern` declarations without an explicit ABI are disallowed
+
+unsafe extern fn _bar() {}
+//[current]~^ WARN `extern` declarations without an explicit ABI are deprecated
+//[current_feature]~^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future]~^^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future_feature]~^^^^ ERROR `extern` declarations without an explicit ABI are disallowed
+
+unsafe extern {}
+//[current]~^ WARN `extern` declarations without an explicit ABI are deprecated
+//[current_feature]~^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future]~^^^ WARN `extern` declarations without an explicit ABI are deprecated
+//[future_feature]~^^^^ ERROR `extern` declarations without an explicit ABI are disallowed
+
+fn main() {}

tests/ui/link-native-libs/suggest-libname-only-1.rs

@@ -2,7 +2,7 @@
 //@ compile-flags: --crate-type rlib
 
 #[link(name = "libfoo.a", kind = "static")]
-extern { } //~ WARN extern declarations without an explicit ABI are deprecated
+extern { } //~ WARN `extern` declarations without an explicit ABI are deprecated
            //~| HELP explicitly specify the "C" ABI
 
 pub fn main() { }

tests/ui/link-native-libs/suggest-libname-only-1.stderr

@@ -1,4 +1,4 @@
-warning: extern declarations without an explicit ABI are deprecated
+warning: `extern` declarations without an explicit ABI are deprecated
   --> $DIR/suggest-libname-only-1.rs:5:1
    |
 LL | extern { }

tests/ui/link-native-libs/suggest-libname-only-2.rs

@@ -2,7 +2,7 @@
 //@ compile-flags: --crate-type rlib
 
 #[link(name = "bar.lib", kind = "static")]
-extern { } //~ WARN extern declarations without an explicit ABI are deprecated
+extern { } //~ WARN `extern` declarations without an explicit ABI are deprecated
            //~| HELP explicitly specify the "C" ABI
 
 pub fn main() { }

tests/ui/link-native-libs/suggest-libname-only-2.stderr

@@ -1,4 +1,4 @@
-warning: extern declarations without an explicit ABI are deprecated
+warning: `extern` declarations without an explicit ABI are deprecated
   --> $DIR/suggest-libname-only-2.rs:5:1
    |
 LL | extern { }

tests/ui/lint/cli-lint-override.forbid_warn.stderr

@@ -1,4 +1,4 @@
-error: extern declarations without an explicit ABI are deprecated
+error: `extern` declarations without an explicit ABI are deprecated
   --> $DIR/cli-lint-override.rs:12:1
    |
 LL | extern fn foo() {}

tests/ui/lint/cli-lint-override.force_warn_deny.stderr

@@ -1,4 +1,4 @@
-warning: extern declarations without an explicit ABI are deprecated
+warning: `extern` declarations without an explicit ABI are deprecated
   --> $DIR/cli-lint-override.rs:12:1
    |
 LL | extern fn foo() {}

tests/ui/lint/cli-lint-override.rs

@@ -10,8 +10,8 @@
 
 
 extern fn foo() {}
-//[warn_deny]~^ ERROR extern declarations without an explicit ABI are deprecated
-//[forbid_warn]~^^ ERROR extern declarations without an explicit ABI are deprecated
-//[force_warn_deny]~^^^ WARN extern declarations without an explicit ABI are deprecated
+//[warn_deny]~^ ERROR `extern` declarations without an explicit ABI are deprecated
+//[forbid_warn]~^^ ERROR `extern` declarations without an explicit ABI are deprecated
+//[force_warn_deny]~^^^ WARN `extern` declarations without an explicit ABI are deprecated
 
 fn main() {}

tests/ui/lint/cli-lint-override.warn_deny.stderr

@@ -1,4 +1,4 @@
-error: extern declarations without an explicit ABI are deprecated
+error: `extern` declarations without an explicit ABI are deprecated
   --> $DIR/cli-lint-override.rs:12:1
    |
 LL | extern fn foo() {}

tests/ui/parser/bad-lit-suffixes.stderr

@@ -51,15 +51,15 @@ LL | #[rustc_layout_scalar_valid_range_start(0suffix)]
    |
    = help: the suffix must be one of the numeric types (`u32`, `isize`, `f32`, etc.)
 
-warning: extern declarations without an explicit ABI are deprecated
+warning: `extern` declarations without an explicit ABI are deprecated
   --> $DIR/bad-lit-suffixes.rs:3:1
    |
 LL | extern
    | ^^^^^^ help: explicitly specify the "C" ABI: `extern "C"`
    |
    = note: `#[warn(missing_abi)]` on by default
 
-warning: extern declarations without an explicit ABI are deprecated
+warning: `extern` declarations without an explicit ABI are deprecated
   --> $DIR/bad-lit-suffixes.rs:7:1
    |
 LL | extern

tests/ui/parser/lit-err-in-macro.stderr

@@ -4,7 +4,7 @@ error: suffixes on string literals are invalid
 LL | f!("Foo"__);
    |    ^^^^^^^ invalid suffix `__`
 
-warning: extern declarations without an explicit ABI are deprecated
+warning: `extern` declarations without an explicit ABI are deprecated
   --> $DIR/lit-err-in-macro.rs:3:9
    |
 LL |         extern $abi fn f() {}

tests/ui/proc-macro/inner-attrs.rs

@@ -82,7 +82,7 @@ fn bar() {
 }
 
 
-extern { //~ WARN extern declarations without an explicit ABI are deprecated
+extern { //~ WARN `extern` declarations without an explicit ABI are deprecated
     fn weird_extern() {
         #![print_target_and_args_consume(tenth)]
     }

tests/ui/proc-macro/inner-attrs.stderr

@@ -22,7 +22,7 @@ error: expected non-macro inner attribute, found attribute macro `print_attr`
 LL |         #![print_attr]
    |            ^^^^^^^^^^ not a non-macro inner attribute
 
-warning: extern declarations without an explicit ABI are deprecated
+warning: `extern` declarations without an explicit ABI are deprecated
   --> $DIR/inner-attrs.rs:85:1
    |
 LL | extern {