refactor: update ABI/Extern handling

Updates to account for changes in
rust-lang/rust#66271

Author: calebcartwright

rustfmt-core/rustfmt-lib/src/items.rs

@@ -195,7 +195,7 @@ impl<'a> Item<'a> {
     fn from_foreign_mod(fm: &'a ast::ForeignMod, span: Span, config: &Config) -> Item<'a> {
         Item {
             keyword: "",
-            abi: format_abi(fm.abi, config.force_explicit_abi(), true),
+            abi: format_extern(ast::Extern::from_abi(fm.abi), config.force_explicit_abi(), true),
             vis: None,
             body: fm
                 .items
@@ -219,7 +219,8 @@ enum BodyElement<'a> {
 pub(crate) struct FnSig<'a> {
     decl: &'a ast::FnDecl,
     generics: &'a ast::Generics,
-    abi: abi::Abi,
+    ext: ast::Extern,
+    // abi: abi::Abi,
     is_async: Cow<'a, ast::IsAsync>,
     constness: ast::Constness,
     defaultness: ast::Defaultness,
@@ -236,7 +237,7 @@ impl<'a> FnSig<'a> {
         FnSig {
             decl,
             generics,
-            abi: abi::Abi::Rust,
+            ext: ast::Extern::None,
             is_async: Cow::Owned(ast::IsAsync::NotAsync),
             constness: ast::Constness::NotConst,
             defaultness: ast::Defaultness::Final,
@@ -246,15 +247,20 @@ impl<'a> FnSig<'a> {
     }
 
     pub(crate) fn from_method_sig(
-        method_sig: &'a ast::MethodSig,
+        method_sig: &'a ast::FnSig,
         generics: &'a ast::Generics,
     ) -> FnSig<'a> {
+        // let abi = match method_sig.header.ext {
+        //     ast::Extern::None => abi::Abi::Rust,
+        //     ast::Extern::Implicit => abi::Abi::C,
+        //     ast::Extern::Explicit(abi) => self.lower_abi(abi),
+        // };
         FnSig {
             unsafety: method_sig.header.unsafety,
             is_async: Cow::Borrowed(&method_sig.header.asyncness.node),
             constness: method_sig.header.constness.node,
             defaultness: ast::Defaultness::Final,
-            abi: method_sig.header.abi,
+            ext: method_sig.header.ext,
             decl: &*method_sig.decl,
             generics,
             visibility: DEFAULT_VISIBILITY,
@@ -271,7 +277,7 @@ impl<'a> FnSig<'a> {
             visit::FnKind::ItemFn(_, fn_header, visibility, _) => FnSig {
                 decl,
                 generics,
-                abi: fn_header.abi,
+                ext: fn_header.ext,
                 constness: fn_header.constness.node,
                 is_async: Cow::Borrowed(&fn_header.asyncness.node),
                 defaultness,
@@ -296,8 +302,8 @@ impl<'a> FnSig<'a> {
         result.push_str(format_constness(self.constness));
         result.push_str(format_async(&self.is_async));
         result.push_str(format_unsafety(self.unsafety));
-        result.push_str(&format_abi(
-            self.abi,
+        result.push_str(&format_extern(
+            self.ext,
             context.config.force_explicit_abi(),
             false,
         ));
@@ -383,7 +389,7 @@ impl<'a> FmtVisitor<'a> {
         &mut self,
         indent: Indent,
         ident: ast::Ident,
-        sig: &ast::MethodSig,
+        sig: &ast::FnSig,
         generics: &ast::Generics,
         span: Span,
     ) -> Option<String> {

rustfmt-core/rustfmt-lib/src/types.rs

@@ -18,7 +18,7 @@ use crate::shape::Shape;
 use crate::source_map::SpanUtils;
 use crate::spanned::Spanned;
 use crate::utils::{
-    colon_spaces, extra_offset, first_line_width, format_abi, format_mutability,
+    colon_spaces, extra_offset, first_line_width, format_extern, format_mutability,
     last_line_extendable, last_line_width, mk_sp, rewrite_ident,
 };
 
@@ -772,8 +772,8 @@ fn rewrite_bare_fn(
 
     result.push_str(crate::utils::format_unsafety(bare_fn.unsafety));
 
-    result.push_str(&format_abi(
-        bare_fn.abi,
+    result.push_str(&format_extern(
+        bare_fn.ext,
         context.config.force_explicit_abi(),
         false,
     ));

rustfmt-core/rustfmt-lib/src/utils.rs

@@ -132,6 +132,16 @@ pub(crate) fn format_mutability(mutability: ast::Mutability) -> &'static str {
     }
 }
 
+#[inline]
+pub(crate) fn format_extern(ext: ast::Extern, explicit_abi: bool, is_mod: bool) -> Cow<'static, str> {
+    match (ext, explicit_abi, is_mod) {
+        (ast::Extern::None, _, false) => Cow::from(""),
+        (ast::Extern::Implicit, false, _) => Cow::from("extern "),
+        (ast::Extern::Explicit(abi), _, _) => Cow::from(format!("extern {} ", abi.symbol_unescaped.as_str())),
+        (_, _, _) => unreachable!(),
+    }
+}
+
 #[inline]
 pub(crate) fn format_abi(abi: abi::Abi, explicit_abi: bool, is_mod: bool) -> Cow<'static, str> {
     if abi == abi::Abi::Rust && !is_mod {