Rollup merge of #135340 - obeis:explicit-extern-abis, r=traviscross,nadrieril

Add `explicit_extern_abis` Feature and Enforce Explicit ABIs

The unstable `explicit_extern_abis` feature is introduced, requiring explicit ABIs in `extern` blocks. Hard errors will be enforced with this feature enabled in a future edition.

RFC rust-lang/rfcs#3722

Update #134986

20 files changed, 287 insertions, 15 deletions

diff --git a/tests/ui/feature-gates/feature-gate-explicit-extern-abis.current.fixed b/tests/ui/feature-gates/feature-gate-explicit-extern-abis.current.fixed
new file mode 100644
index 00000000000..525f78d162f
--- /dev/null
+++ b/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() {}
diff --git a/tests/ui/feature-gates/feature-gate-explicit-extern-abis.current.stderr b/tests/ui/feature-gates/feature-gate-explicit-extern-abis.current.stderr
new file mode 100644
index 00000000000..cf927807c7c
--- /dev/null
+++ b/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
+
diff --git a/tests/ui/feature-gates/feature-gate-explicit-extern-abis.current_feature.fixed b/tests/ui/feature-gates/feature-gate-explicit-extern-abis.current_feature.fixed
new file mode 100644
index 00000000000..525f78d162f
--- /dev/null
+++ b/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() {}
diff --git a/tests/ui/feature-gates/feature-gate-explicit-extern-abis.current_feature.stderr b/tests/ui/feature-gates/feature-gate-explicit-extern-abis.current_feature.stderr
new file mode 100644
index 00000000000..cf927807c7c
--- /dev/null
+++ b/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
+
diff --git a/tests/ui/feature-gates/feature-gate-explicit-extern-abis.future.fixed b/tests/ui/feature-gates/feature-gate-explicit-extern-abis.future.fixed
new file mode 100644
index 00000000000..525f78d162f
--- /dev/null
+++ b/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() {}
diff --git a/tests/ui/feature-gates/feature-gate-explicit-extern-abis.future.stderr b/tests/ui/feature-gates/feature-gate-explicit-extern-abis.future.stderr
new file mode 100644
index 00000000000..cf927807c7c
--- /dev/null
+++ b/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
+
diff --git a/tests/ui/feature-gates/feature-gate-explicit-extern-abis.future_feature.stderr b/tests/ui/feature-gates/feature-gate-explicit-extern-abis.future_feature.stderr
new file mode 100644
index 00000000000..096a6f43416
--- /dev/null
+++ b/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
+
diff --git a/tests/ui/feature-gates/feature-gate-explicit-extern-abis.rs b/tests/ui/feature-gates/feature-gate-explicit-extern-abis.rs
new file mode 100644
index 00000000000..379c45f5899
--- /dev/null
+++ b/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() {}
diff --git a/tests/ui/link-native-libs/suggest-libname-only-1.rs b/tests/ui/link-native-libs/suggest-libname-only-1.rs
index c69949d1fdb..8699e4819e6 100644
--- a/tests/ui/link-native-libs/suggest-libname-only-1.rs
+++ b/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() { }
diff --git a/tests/ui/link-native-libs/suggest-libname-only-1.stderr b/tests/ui/link-native-libs/suggest-libname-only-1.stderr
index 0320294a800..59bd99f619a 100644
--- a/tests/ui/link-native-libs/suggest-libname-only-1.stderr
+++ b/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 { }
diff --git a/tests/ui/link-native-libs/suggest-libname-only-2.rs b/tests/ui/link-native-libs/suggest-libname-only-2.rs
index d5150c327cd..87373f563d0 100644
--- a/tests/ui/link-native-libs/suggest-libname-only-2.rs
+++ b/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() { }
diff --git a/tests/ui/link-native-libs/suggest-libname-only-2.stderr b/tests/ui/link-native-libs/suggest-libname-only-2.stderr
index e492aea27b4..298a9ced170 100644
--- a/tests/ui/link-native-libs/suggest-libname-only-2.stderr
+++ b/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 { }
diff --git a/tests/ui/lint/cli-lint-override.forbid_warn.stderr b/tests/ui/lint/cli-lint-override.forbid_warn.stderr
index fb8779ad4f1..fe3437ae3d7 100644
--- a/tests/ui/lint/cli-lint-override.forbid_warn.stderr
+++ b/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() {}
diff --git a/tests/ui/lint/cli-lint-override.force_warn_deny.stderr b/tests/ui/lint/cli-lint-override.force_warn_deny.stderr
index 10fc13e3f52..f48fca4bd9f 100644
--- a/tests/ui/lint/cli-lint-override.force_warn_deny.stderr
+++ b/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() {}
diff --git a/tests/ui/lint/cli-lint-override.rs b/tests/ui/lint/cli-lint-override.rs
index 4b3fd0d9c01..b733872166a 100644
--- a/tests/ui/lint/cli-lint-override.rs
+++ b/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() {}
diff --git a/tests/ui/lint/cli-lint-override.warn_deny.stderr b/tests/ui/lint/cli-lint-override.warn_deny.stderr
index 979ca22324f..91baad1f9f8 100644
--- a/tests/ui/lint/cli-lint-override.warn_deny.stderr
+++ b/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() {}
diff --git a/tests/ui/parser/bad-lit-suffixes.stderr b/tests/ui/parser/bad-lit-suffixes.stderr
index d6b50b0e0d1..86ef35bf783 100644
--- a/tests/ui/parser/bad-lit-suffixes.stderr
+++ b/tests/ui/parser/bad-lit-suffixes.stderr
@@ -51,7 +51,7 @@ 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
@@ -59,7 +59,7 @@ LL | extern
    |
    = 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
diff --git a/tests/ui/parser/lit-err-in-macro.stderr b/tests/ui/parser/lit-err-in-macro.stderr
index 9422f22f9c8..08fe58643d4 100644
--- a/tests/ui/parser/lit-err-in-macro.stderr
+++ b/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() {}
diff --git a/tests/ui/proc-macro/inner-attrs.rs b/tests/ui/proc-macro/inner-attrs.rs
index c541e93f904..ca4b2029a33 100644
--- a/tests/ui/proc-macro/inner-attrs.rs
+++ b/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)]
     }
diff --git a/tests/ui/proc-macro/inner-attrs.stderr b/tests/ui/proc-macro/inner-attrs.stderr
index 4e7825c0d00..54cccae8da0 100644
--- a/tests/ui/proc-macro/inner-attrs.stderr
+++ b/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 {