Fix bad replacement for unsafe extern block suggestion

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -464,7 +464,7 @@ impl<'a> AstValidator<'a> {
                 {
                     self.dcx().emit_err(errors::InvalidSafetyOnExtern {
                         item_span: span,
-                        block: self.current_extern_span(),
+                        block: self.current_extern_span().shrink_to_lo(),
                     });
                 }
             }

compiler/rustc_ast_passes/src/errors.rs

@@ -221,7 +221,7 @@ pub enum ExternBlockSuggestion {
 pub struct InvalidSafetyOnExtern {
     #[primary_span]
     pub item_span: Span,
-    #[suggestion(code = "", applicability = "maybe-incorrect")]
+    #[suggestion(code = "unsafe ", applicability = "machine-applicable", style = "verbose")]
     pub block: Span,
 }
 

tests/ui/parser/fn-header-semantic-fail.stderr

@@ -81,11 +81,13 @@ LL |         async fn fe1();
 error: items in unadorned `extern` blocks cannot have safety qualifiers
   --> $DIR/fn-header-semantic-fail.rs:47:9
    |
-LL |     extern "C" {
-   |     ---------- help: add unsafe to this `extern` block
-LL |         async fn fe1();
 LL |         unsafe fn fe2();
    |         ^^^^^^^^^^^^^^^^
+   |
+help: add unsafe to this `extern` block
+   |
+LL |     unsafe extern "C" {
+   |     ++++++
 
 error: functions in `extern` blocks cannot have qualifiers
   --> $DIR/fn-header-semantic-fail.rs:48:9
@@ -135,11 +137,13 @@ LL |         const async unsafe extern "C" fn fe5();
 error: items in unadorned `extern` blocks cannot have safety qualifiers
   --> $DIR/fn-header-semantic-fail.rs:50:9
    |
-LL |     extern "C" {
-   |     ---------- help: add unsafe to this `extern` block
-...
 LL |         const async unsafe extern "C" fn fe5();
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: add unsafe to this `extern` block
+   |
+LL |     unsafe extern "C" {
+   |     ++++++
 
 error: functions cannot be both `const` and `async`
   --> $DIR/fn-header-semantic-fail.rs:50:9

tests/ui/parser/no-const-fn-in-extern-block.stderr

@@ -18,11 +18,13 @@ LL |     const unsafe fn bar();
 error: items in unadorned `extern` blocks cannot have safety qualifiers
   --> $DIR/no-const-fn-in-extern-block.rs:4:5
    |
-LL | extern "C" {
-   | ---------- help: add unsafe to this `extern` block
-...
 LL |     const unsafe fn bar();
    |     ^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: add unsafe to this `extern` block
+   |
+LL | unsafe extern "C" {
+   | ++++++
 
 error: aborting due to 3 previous errors
 

tests/ui/parser/unsafe-foreign-mod-2.stderr

@@ -13,11 +13,13 @@ LL | extern "C" unsafe {
 error: items in unadorned `extern` blocks cannot have safety qualifiers
   --> $DIR/unsafe-foreign-mod-2.rs:4:5
    |
-LL | extern "C" unsafe {
-   | ----------------- help: add unsafe to this `extern` block
-...
 LL |     unsafe fn foo();
    |     ^^^^^^^^^^^^^^^^
+   |
+help: add unsafe to this `extern` block
+   |
+LL | unsafe extern "C" unsafe {
+   | ++++++
 
 error: aborting due to 3 previous errors
 

tests/ui/rust-2024/unsafe-extern-blocks/safe-unsafe-on-unadorned-extern-block.edition2021.stderr

@@ -1,20 +1,24 @@
 error: items in unadorned `extern` blocks cannot have safety qualifiers
   --> $DIR/safe-unsafe-on-unadorned-extern-block.rs:10:5
    |
-LL | extern "C" {
-   | ---------- help: add unsafe to this `extern` block
-LL |
 LL |     safe static TEST1: i32;
    |     ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: add unsafe to this `extern` block
+   |
+LL | unsafe extern "C" {
+   | ++++++
 
 error: items in unadorned `extern` blocks cannot have safety qualifiers
   --> $DIR/safe-unsafe-on-unadorned-extern-block.rs:12:5
    |
-LL | extern "C" {
-   | ---------- help: add unsafe to this `extern` block
-...
 LL |     safe fn test1(i: i32);
    |     ^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: add unsafe to this `extern` block
+   |
+LL | unsafe extern "C" {
+   | ++++++
 
 error: aborting due to 2 previous errors
 

tests/ui/rust-2024/unsafe-extern-blocks/safe-unsafe-on-unadorned-extern-block.edition2024.stderr

@@ -13,20 +13,24 @@ LL | | }
 error: items in unadorned `extern` blocks cannot have safety qualifiers
   --> $DIR/safe-unsafe-on-unadorned-extern-block.rs:10:5
    |
-LL | extern "C" {
-   | ---------- help: add unsafe to this `extern` block
-LL |
 LL |     safe static TEST1: i32;
    |     ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: add unsafe to this `extern` block
+   |
+LL | unsafe extern "C" {
+   | ++++++
 
 error: items in unadorned `extern` blocks cannot have safety qualifiers
   --> $DIR/safe-unsafe-on-unadorned-extern-block.rs:12:5
    |
-LL | extern "C" {
-   | ---------- help: add unsafe to this `extern` block
-...
 LL |     safe fn test1(i: i32);
    |     ^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: add unsafe to this `extern` block
+   |
+LL | unsafe extern "C" {
+   | ++++++
 
 error: aborting due to 3 previous errors
 

tests/ui/rust-2024/unsafe-extern-blocks/unsafe-on-extern-block-issue-126756.fixed

@@ -0,0 +1,10 @@
+//@ run-rustfix
+
+#![feature(unsafe_extern_blocks)]
+#![allow(dead_code)]
+
+unsafe extern "C" {
+    unsafe fn foo(); //~ ERROR items in unadorned `extern` blocks cannot have safety qualifiers
+}
+
+fn main() {}

tests/ui/rust-2024/unsafe-extern-blocks/unsafe-on-extern-block-issue-126756.rs

@@ -0,0 +1,10 @@
+//@ run-rustfix
+
+#![feature(unsafe_extern_blocks)]
+#![allow(dead_code)]
+
+extern "C" {
+    unsafe fn foo(); //~ ERROR items in unadorned `extern` blocks cannot have safety qualifiers
+}
+
+fn main() {}

tests/ui/rust-2024/unsafe-extern-blocks/unsafe-on-extern-block-issue-126756.stderr

@@ -0,0 +1,13 @@
+error: items in unadorned `extern` blocks cannot have safety qualifiers
+  --> $DIR/unsafe-on-extern-block-issue-126756.rs:7:5
+   |
+LL |     unsafe fn foo();
+   |     ^^^^^^^^^^^^^^^^
+   |
+help: add unsafe to this `extern` block
+   |
+LL | unsafe extern "C" {
+   | ++++++
+
+error: aborting due to 1 previous error
+