Rollup merge of #66271 - petrochenkov:abism, r=Centril

syntax: Keep string literals in ABIs and `asm!` more precisely

As a result we don't lose spans when `extern` functions or blocks are passed to proc macros, and also escape all string literals consistently.
Continuation of https://github.com/rust-lang/rust/pull/60679, which did a similar thing with all literals besides those in ABIs and `asm!`.

TODO: Add tests.

Fixes https://github.com/rust-lang/rust/issues/60493
Fixes https://github.com/rust-lang/rust/issues/64561
r? @Centril

4 files changed, 74 insertions, 40 deletions

diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index d358efbe543..bbf00825acb 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -1422,6 +1422,33 @@ pub struct Lit {
     pub span: Span,
 }
 
+/// Same as `Lit`, but restricted to string literals.
+#[derive(Clone, Copy, RustcEncodable, RustcDecodable, Debug)]
+pub struct StrLit {
+    /// The original literal token as written in source code.
+    pub style: StrStyle,
+    pub symbol: Symbol,
+    pub suffix: Option<Symbol>,
+    pub span: Span,
+    /// The unescaped "semantic" representation of the literal lowered from the original token.
+    /// FIXME: Remove this and only create the semantic representation during lowering to HIR.
+    pub symbol_unescaped: Symbol,
+}
+
+impl StrLit {
+    crate fn as_lit(&self) -> Lit {
+        let token_kind = match self.style {
+            StrStyle::Cooked => token::Str,
+            StrStyle::Raw(n) => token::StrRaw(n),
+        };
+        Lit {
+            token: token::Lit::new(token_kind, self.symbol, self.suffix),
+            span: self.span,
+            kind: LitKind::Str(self.symbol_unescaped, self.style),
+        }
+    }
+}
+
 // Clippy uses Hash and PartialEq
 /// Type of the integer literal based on provided suffix.
 #[derive(Clone, Copy, RustcEncodable, RustcDecodable, Debug, Hash, PartialEq)]
@@ -1745,7 +1772,7 @@ pub struct Ty {
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
 pub struct BareFnTy {
     pub unsafety: Unsafety,
-    pub abi: Abi,
+    pub ext: Extern,
     pub generic_params: Vec<GenericParam>,
     pub decl: P<FnDecl>,
 }
@@ -2128,7 +2155,7 @@ pub struct Mod {
 /// E.g., `extern { .. }` or `extern C { .. }`.
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
 pub struct ForeignMod {
-    pub abi: Abi,
+    pub abi: Option<StrLit>,
     pub items: Vec<ForeignItem>,
 }
 
@@ -2411,24 +2438,17 @@ impl Item {
     }
 }
 
-/// A reference to an ABI.
-///
-/// In AST our notion of an ABI is still syntactic unlike in `rustc_target::spec::abi::Abi`.
-#[derive(Clone, Copy, RustcEncodable, RustcDecodable, Debug, PartialEq)]
-pub struct Abi {
-    pub symbol: Symbol,
-    pub span: Span,
-}
-
-impl Abi {
-    pub fn new(symbol: Symbol, span: Span) -> Self {
-        Self { symbol, span }
-    }
+/// `extern` qualifier on a function item or function type.
+#[derive(Clone, Copy, RustcEncodable, RustcDecodable, Debug)]
+pub enum Extern {
+    None,
+    Implicit,
+    Explicit(StrLit),
 }
 
-impl Default for Abi {
-    fn default() -> Self {
-        Self::new(sym::Rust, DUMMY_SP)
+impl Extern {
+    pub fn from_abi(abi: Option<StrLit>) -> Extern {
+        abi.map_or(Extern::Implicit, Extern::Explicit)
     }
 }
 
@@ -2441,7 +2461,7 @@ pub struct FnHeader {
     pub unsafety: Unsafety,
     pub asyncness: Spanned<IsAsync>,
     pub constness: Spanned<Constness>,
-    pub abi: Abi,
+    pub ext: Extern,
 }
 
 impl Default for FnHeader {
@@ -2450,7 +2470,7 @@ impl Default for FnHeader {
             unsafety: Unsafety::Normal,
             asyncness: dummy_spanned(IsAsync::NotAsync),
             constness: dummy_spanned(Constness::NotConst),
-            abi: Abi::default(),
+            ext: Extern::None,
         }
     }
 }
diff --git a/src/libsyntax/feature_gate/check.rs b/src/libsyntax/feature_gate/check.rs
index bd836eee42a..abf9adefd3c 100644
--- a/src/libsyntax/feature_gate/check.rs
+++ b/src/libsyntax/feature_gate/check.rs
@@ -191,10 +191,10 @@ macro_rules! gate_feature_post {
 }
 
 impl<'a> PostExpansionVisitor<'a> {
-    fn check_abi(&self, abi: ast::Abi) {
-        let ast::Abi { symbol, span } = abi;
+    fn check_abi(&self, abi: ast::StrLit) {
+        let ast::StrLit { symbol_unescaped, span, .. } = abi;
 
-        match &*symbol.as_str() {
+        match &*symbol_unescaped.as_str() {
             // Stable
             "Rust" |
             "C" |
@@ -258,6 +258,12 @@ impl<'a> PostExpansionVisitor<'a> {
         }
     }
 
+    fn check_extern(&self, ext: ast::Extern) {
+        if let ast::Extern::Explicit(abi) = ext {
+            self.check_abi(abi);
+        }
+    }
+
     fn maybe_report_invalid_custom_discriminants(&self, variants: &[ast::Variant]) {
         let has_fields = variants.iter().any(|variant| match variant.data {
             VariantData::Tuple(..) | VariantData::Struct(..) => true,
@@ -388,7 +394,9 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
     fn visit_item(&mut self, i: &'a ast::Item) {
         match i.kind {
             ast::ItemKind::ForeignMod(ref foreign_module) => {
-                self.check_abi(foreign_module.abi);
+                if let Some(abi) = foreign_module.abi {
+                    self.check_abi(abi);
+                }
             }
 
             ast::ItemKind::Fn(..) => {
@@ -511,7 +519,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
     fn visit_ty(&mut self, ty: &'a ast::Ty) {
         match ty.kind {
             ast::TyKind::BareFn(ref bare_fn_ty) => {
-                self.check_abi(bare_fn_ty.abi);
+                self.check_extern(bare_fn_ty.ext);
             }
             ast::TyKind::Never => {
                 gate_feature_post!(&self, never_type, ty.span,
@@ -605,7 +613,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
             // Stability of const fn methods are covered in
             // `visit_trait_item` and `visit_impl_item` below; this is
             // because default methods don't pass through this point.
-            self.check_abi(header.abi);
+            self.check_extern(header.ext);
         }
 
         if fn_decl.c_variadic() {
@@ -639,7 +647,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
         match ti.kind {
             ast::TraitItemKind::Method(ref sig, ref block) => {
                 if block.is_none() {
-                    self.check_abi(sig.header.abi);
+                    self.check_extern(sig.header.ext);
                 }
                 if sig.decl.c_variadic() {
                     gate_feature_post!(&self, c_variadic, ti.span,
diff --git a/src/libsyntax/mut_visit.rs b/src/libsyntax/mut_visit.rs
index f4ef993edb9..da3c885b860 100644
--- a/src/libsyntax/mut_visit.rs
+++ b/src/libsyntax/mut_visit.rs
@@ -441,7 +441,7 @@ pub fn noop_visit_ty<T: MutVisitor>(ty: &mut P<Ty>, vis: &mut T) {
             vis.visit_mt(mt);
         }
         TyKind::BareFn(bft) => {
-            let BareFnTy { unsafety: _, abi: _, generic_params, decl } = bft.deref_mut();
+            let BareFnTy { unsafety: _, ext: _, generic_params, decl } = bft.deref_mut();
             generic_params.flat_map_in_place(|param| vis.flat_map_generic_param(param));
             vis.visit_fn_decl(decl);
         }
@@ -974,7 +974,7 @@ pub fn noop_flat_map_impl_item<T: MutVisitor>(mut item: ImplItem, visitor: &mut
 }
 
 pub fn noop_visit_fn_header<T: MutVisitor>(header: &mut FnHeader, vis: &mut T) {
-    let FnHeader { unsafety: _, asyncness, constness: _, abi: _ } = header;
+    let FnHeader { unsafety: _, asyncness, constness: _, ext: _ } = header;
     vis.visit_asyncness(&mut asyncness.node);
 }
 
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index ef65a744e83..17a7cbddff9 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -1013,7 +1013,7 @@ impl<'a> State<'a> {
                 self.pclose();
             }
             ast::TyKind::BareFn(ref f) => {
-                self.print_ty_fn(f.abi,
+                self.print_ty_fn(f.ext,
                                  f.unsafety,
                                  &f.decl,
                                  None,
@@ -1232,7 +1232,10 @@ impl<'a> State<'a> {
             }
             ast::ItemKind::ForeignMod(ref nmod) => {
                 self.head("extern");
-                self.print_abi(nmod.abi);
+                if let Some(abi) = nmod.abi {
+                    self.print_literal(&abi.as_lit());
+                    self.nbsp();
+                }
                 self.bopen();
                 self.print_foreign_mod(nmod, &item.attrs);
                 self.bclose(item.span);
@@ -2805,7 +2808,7 @@ impl<'a> State<'a> {
     }
 
     crate fn print_ty_fn(&mut self,
-                       abi: ast::Abi,
+                       ext: ast::Extern,
                        unsafety: ast::Unsafety,
                        decl: &ast::FnDecl,
                        name: Option<ast::Ident>,
@@ -2825,7 +2828,7 @@ impl<'a> State<'a> {
             span: syntax_pos::DUMMY_SP,
         };
         self.print_fn(decl,
-                      ast::FnHeader { unsafety, abi, ..ast::FnHeader::default() },
+                      ast::FnHeader { unsafety, ext, ..ast::FnHeader::default() },
                       name,
                       &generics,
                       &source_map::dummy_spanned(ast::VisibilityKind::Inherited));
@@ -2866,18 +2869,21 @@ impl<'a> State<'a> {
         self.print_asyncness(header.asyncness.node);
         self.print_unsafety(header.unsafety);
 
-        if header.abi.symbol != sym::Rust {
-            self.word_nbsp("extern");
-            self.print_abi(header.abi);
+        match header.ext {
+            ast::Extern::None => {}
+            ast::Extern::Implicit => {
+                self.word_nbsp("extern");
+            }
+            ast::Extern::Explicit(abi) => {
+                self.word_nbsp("extern");
+                self.print_literal(&abi.as_lit());
+                self.nbsp();
+            }
         }
 
         self.s.word("fn")
     }
 
-    fn print_abi(&mut self, abi: ast::Abi) {
-        self.word_nbsp(format!("\"{}\"", abi.symbol));
-    }
-
     crate fn print_unsafety(&mut self, s: ast::Unsafety) {
         match s {
             ast::Unsafety::Normal => {},