rustdoc: Display `extern "C" fn` instead of `extern fn`

src/librustdoc/html/format.rs

@@ -1177,7 +1177,6 @@ impl fmt::Display for AbiSpace {
         let quot = if f.alternate() { "\"" } else { """ };
         match self.0 {
             Abi::Rust => Ok(()),
-            Abi::C => write!(f, "extern "),
             abi => write!(f, "extern {0}{1}{0} ", quot, abi.name()),
         }
     }

src/test/rustdoc/extern-impl.rs

@@ -18,9 +18,9 @@ impl Foo {
     pub fn rust0() {}
     // @has - '//code' 'fn rust1()'
     pub extern "Rust" fn rust1() {}
-    // @has - '//code' 'extern fn c0()'
+    // @has - '//code' 'extern "C" fn c0()'
     pub extern fn c0() {}
-    // @has - '//code' 'extern fn c1()'
+    // @has - '//code' 'extern "C" fn c1()'
     pub extern "C" fn c1() {}
     // @has - '//code' 'extern "system" fn system0()'
     pub extern "system" fn system0() {}
@@ -31,7 +31,7 @@ pub trait Bar {}
 
 // @has - '//code' 'impl Bar for fn()'
 impl Bar for fn() {}
-// @has - '//code' 'impl Bar for extern fn()'
+// @has - '//code' 'impl Bar for extern "C" fn()'
 impl Bar for extern fn() {}
 // @has - '//code' 'impl Bar for extern "system" fn()'
 impl Bar for extern "system" fn() {}

src/test/rustdoc/ffi.rs

@@ -13,10 +13,10 @@
 
 extern crate rustdoc_ffi as lib;
 
-// @has ffi/fn.foreigner.html //pre 'pub unsafe extern fn foreigner(cold_as_ice: u32)'
+// @has ffi/fn.foreigner.html //pre 'pub unsafe extern "C" fn foreigner(cold_as_ice: u32)'
 pub use lib::foreigner;
 
 extern "C" {
-    // @has ffi/fn.another.html //pre 'pub unsafe extern fn another(cold_as_ice: u32)'
+    // @has ffi/fn.another.html //pre 'pub unsafe extern "C" fn another(cold_as_ice: u32)'
     pub fn another(cold_as_ice: u32);
 }

src/test/rustdoc/issue-22038.rs

@@ -10,7 +10,7 @@
 
 extern {
     // @has issue_22038/fn.foo1.html \
-    //      '//*[@class="rust fn"]' 'pub unsafe extern fn foo1()'
+    //      '//*[@class="rust fn"]' 'pub unsafe extern "C" fn foo1()'
     pub fn foo1();
 }
 
@@ -21,7 +21,7 @@ extern "system" {
 }
 
 // @has issue_22038/fn.bar.html \
-//      '//*[@class="rust fn"]' 'pub extern fn bar()'
+//      '//*[@class="rust fn"]' 'pub extern "C" fn bar()'
 pub extern fn bar() {}
 
 // @has issue_22038/fn.baz.html \

src/test/rustdoc/variadic.rs

@@ -9,6 +9,6 @@
 // except according to those terms.
 
 extern "C" {
-    // @has variadic/fn.foo.html //pre 'pub unsafe extern fn foo(x: i32, ...)'
+    // @has variadic/fn.foo.html //pre 'pub unsafe extern "C" fn foo(x: i32, ...)'
     pub fn foo(x: i32, ...);
 }