Allow unsafe extern on all editions

Author: spastorino

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -1016,15 +1016,12 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 walk_list!(self, visit_attribute, &item.attrs);
                 return; // Avoid visiting again.
             }
-            ItemKind::ForeignMod(ForeignMod { abi, safety, .. }) => {
+            ItemKind::ForeignMod(ForeignMod { abi, .. }) => {
                 let old_item = mem::replace(&mut self.extern_mod, Some(item));
                 self.visibility_not_permitted(
                     &item.vis,
                     errors::VisibilityNotPermittedNote::IndividualForeignItems,
                 );
-                if let &Safety::Unsafe(span) = safety {
-                    self.dcx().emit_err(errors::UnsafeItem { span, kind: "extern block" });
-                }
                 if abi.is_none() {
                     self.maybe_lint_missing_abi(item.span, item.id);
                 }

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

@@ -1,8 +1,7 @@
 extern "C" unsafe {
-               //~^ ERROR expected `{`, found keyword `unsafe`
-               //~| ERROR extern block cannot be declared unsafe
+    //~^ ERROR expected `{`, found keyword `unsafe`
     unsafe fn foo();
-        //~^ ERROR functions in `extern` blocks cannot have qualifiers
+    //~^ ERROR functions in `extern` blocks cannot have qualifiers
 }
 
 fn main() {}

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

@@ -4,20 +4,14 @@ error: expected `{`, found keyword `unsafe`
 LL | extern "C" unsafe {
    |            ^^^^^^ expected `{`
 
-error: extern block cannot be declared unsafe
-  --> $DIR/unsafe-foreign-mod-2.rs:1:12
-   |
-LL | extern "C" unsafe {
-   |            ^^^^^^
-
 error: functions in `extern` blocks cannot have qualifiers
-  --> $DIR/unsafe-foreign-mod-2.rs:4:5
+  --> $DIR/unsafe-foreign-mod-2.rs:3:5
    |
 LL | extern "C" unsafe {
    | ----------------- in this `extern` block
-...
+LL |
 LL |     unsafe fn foo();
    |     ^^^^^^ help: remove this qualifier
 
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 

tests/ui/parser/unsafe-foreign-mod.rs

@@ -1,5 +1,5 @@
-unsafe extern "C" {
-    //~^ ERROR extern block cannot be declared unsafe
-}
+//@ build-pass
+
+unsafe extern "C" {}
 
 fn main() {}

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

@@ -1,10 +1,11 @@
+//@ build-pass
+
 extern "C" {
     static TEST1: i32;
     fn test1(i: i32);
 }
 
 unsafe extern "C" {
-    //~^ ERROR: extern block cannot be declared unsafe
     static TEST2: i32;
     fn test2(i: i32);
 }