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

src/librustc/hir/lowering.rs

@@ -1219,7 +1219,7 @@ impl<'a> LoweringContext<'a> {
                                     ImplTraitContext::disallowed(),
                                 ),
                                 unsafety: f.unsafety,
-                                abi: this.lower_abi(f.abi),
+                                abi: this.lower_extern(f.ext),
                                 decl: this.lower_fn_decl(&f.decl, None, false, None),
                                 param_names: this.lower_fn_params_to_names(&f.decl),
                             }))

src/librustc/hir/lowering/item.rs

@@ -735,7 +735,7 @@ impl LoweringContext<'_> {
 
     fn lower_foreign_mod(&mut self, fm: &ForeignMod) -> hir::ForeignMod {
         hir::ForeignMod {
-            abi: self.lower_abi(fm.abi),
+            abi: fm.abi.map_or(abi::Abi::C, |abi| self.lower_abi(abi)),
             items: fm.items
                 .iter()
                 .map(|x| self.lower_foreign_item(x))
@@ -1283,18 +1283,26 @@ impl LoweringContext<'_> {
             unsafety: h.unsafety,
             asyncness: self.lower_asyncness(h.asyncness.node),
             constness: h.constness.node,
-            abi: self.lower_abi(h.abi),
+            abi: self.lower_extern(h.ext),
         }
     }
 
-    pub(super) fn lower_abi(&mut self, abi: Abi) -> abi::Abi {
-        abi::lookup(&abi.symbol.as_str()).unwrap_or_else(|| {
+    pub(super) fn lower_abi(&mut self, abi: StrLit) -> abi::Abi {
+        abi::lookup(&abi.symbol_unescaped.as_str()).unwrap_or_else(|| {
             self.error_on_invalid_abi(abi);
             abi::Abi::Rust
         })
     }
 
-    fn error_on_invalid_abi(&self, abi: Abi) {
+    pub(super) fn lower_extern(&mut self, ext: Extern) -> abi::Abi {
+        match ext {
+            Extern::None => abi::Abi::Rust,
+            Extern::Implicit => abi::Abi::C,
+            Extern::Explicit(abi) => self.lower_abi(abi),
+        }
+    }
+
+    fn error_on_invalid_abi(&self, abi: StrLit) {
         struct_span_err!(
             self.sess,
             abi.span,

src/librustc_parse/parser/expr.rs

@@ -778,13 +778,12 @@ impl<'a> Parser<'a> {
 
         macro_rules! parse_lit {
             () => {
-                match self.parse_lit() {
-                    Ok(literal) => {
+                match self.parse_opt_lit() {
+                    Some(literal) => {
                         hi = self.prev_span;
                         ex = ExprKind::Lit(literal);
                     }
-                    Err(mut err) => {
-                        err.cancel();
+                    None => {
                         return Err(self.expected_expression_found());
                     }
                 }
@@ -1074,11 +1073,39 @@ impl<'a> Parser<'a> {
         self.maybe_recover_from_bad_qpath(expr, true)
     }
 
-    /// Matches `lit = true | false | token_lit`.
+    /// Returns a string literal if the next token is a string literal.
+    /// In case of error returns `Some(lit)` if the next token is a literal with a wrong kind,
+    /// and returns `None` if the next token is not literal at all.
+    pub fn parse_str_lit(&mut self) -> Result<ast::StrLit, Option<Lit>> {
+        match self.parse_opt_lit() {
+            Some(lit) => match lit.kind {
+                ast::LitKind::Str(symbol_unescaped, style) => Ok(ast::StrLit {
+                    style,
+                    symbol: lit.token.symbol,
+                    suffix: lit.token.suffix,
+                    span: lit.span,
+                    symbol_unescaped,
+                }),
+                _ => Err(Some(lit)),
+            }
+            None => Err(None),
+        }
+    }
+
     pub(super) fn parse_lit(&mut self) -> PResult<'a, Lit> {
+        self.parse_opt_lit().ok_or_else(|| {
+            let msg = format!("unexpected token: {}", self.this_token_descr());
+            self.span_fatal(self.token.span, &msg)
+        })
+    }
+
+    /// Matches `lit = true | false | token_lit`.
+    /// Returns `None` if the next token is not a literal.
+    pub(super) fn parse_opt_lit(&mut self) -> Option<Lit> {
         let mut recovered = None;
         if self.token == token::Dot {
-            // Attempt to recover `.4` as `0.4`.
+            // Attempt to recover `.4` as `0.4`. We don't currently have any syntax where
+            // dot would follow an optional literal, so we do this unconditionally.
             recovered = self.look_ahead(1, |next_token| {
                 if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix })
                         = next_token.kind {
@@ -1107,11 +1134,10 @@ impl<'a> Parser<'a> {
         match Lit::from_token(token) {
             Ok(lit) => {
                 self.bump();
-                Ok(lit)
+                Some(lit)
             }
             Err(LitError::NotLiteral) => {
-                let msg = format!("unexpected token: {}", self.this_token_descr());
-                Err(self.span_fatal(token.span, &msg))
+                None
             }
             Err(err) => {
                 let span = token.span;
@@ -1120,18 +1146,18 @@ impl<'a> Parser<'a> {
                     _ => unreachable!(),
                 };
                 self.bump();
-                self.error_literal_from_token(err, lit, span);
+                self.report_lit_error(err, lit, span);
                 // Pack possible quotes and prefixes from the original literal into
                 // the error literal's symbol so they can be pretty-printed faithfully.
                 let suffixless_lit = token::Lit::new(lit.kind, lit.symbol, None);
                 let symbol = Symbol::intern(&suffixless_lit.to_string());
                 let lit = token::Lit::new(token::Err, symbol, lit.suffix);
-                Lit::from_lit_token(lit, span).map_err(|_| unreachable!())
+                Some(Lit::from_lit_token(lit, span).unwrap_or_else(|_| unreachable!()))
             }
         }
     }
 
-    fn error_literal_from_token(&self, err: LitError, lit: token::Lit, span: Span) {
+    fn report_lit_error(&self, err: LitError, lit: token::Lit, span: Span) {
         // Checks if `s` looks like i32 or u1234 etc.
         fn looks_like_width_suffix(first_chars: &[char], s: &str) -> bool {
             s.len() > 1

src/librustc_parse/parser/item.rs

@@ -3,9 +3,9 @@ use super::diagnostics::{Error, dummy_arg, ConsumeClosingDelim};
 
 use crate::maybe_whole;
 
-use syntax::ast::{self, Abi, DUMMY_NODE_ID, Ident, Attribute, AttrKind, AttrStyle, AnonConst, Item};
+use syntax::ast::{self, DUMMY_NODE_ID, Ident, Attribute, AttrKind, AttrStyle, AnonConst, Item};
 use syntax::ast::{ItemKind, ImplItem, ImplItemKind, TraitItem, TraitItemKind, UseTree, UseTreeKind};
-use syntax::ast::{PathSegment, IsAuto, Constness, IsAsync, Unsafety, Defaultness};
+use syntax::ast::{PathSegment, IsAuto, Constness, IsAsync, Unsafety, Defaultness, Extern, StrLit};
 use syntax::ast::{Visibility, VisibilityKind, Mutability, FnHeader, ForeignItem, ForeignItemKind};
 use syntax::ast::{Ty, TyKind, Generics, TraitRef, EnumDef, VariantData, StructField};
 use syntax::ast::{Mac, MacDelimiter, Block, BindingMode, FnDecl, FnSig, SelfKind, Param};
@@ -105,7 +105,7 @@ impl<'a> Parser<'a> {
                 return Ok(Some(self.parse_item_extern_crate(lo, vis, attrs)?));
             }
 
-            let abi = self.parse_opt_abi()?;
+            let abi = self.parse_abi();
 
             if self.eat_keyword(kw::Fn) {
                 // EXTERN FUNCTION ITEM
@@ -114,7 +114,7 @@ impl<'a> Parser<'a> {
                     unsafety: Unsafety::Normal,
                     asyncness: respan(fn_span, IsAsync::NotAsync),
                     constness: respan(fn_span, Constness::NotConst),
-                    abi,
+                    ext: Extern::from_abi(abi),
                 };
                 return self.parse_item_fn(lo, vis, attrs, header);
             } else if self.check(&token::OpenDelim(token::Brace)) {
@@ -143,14 +143,14 @@ impl<'a> Parser<'a> {
                 if self.check_keyword(kw::Extern) {
                     self.sess.gated_spans.gate(sym::const_extern_fn, lo.to(self.token.span));
                 }
-                let abi = self.parse_extern_abi()?;
+                let ext = self.parse_extern()?;
                 self.bump(); // `fn`
 
                 let header = FnHeader {
                     unsafety,
                     asyncness: respan(const_span, IsAsync::NotAsync),
                     constness: respan(const_span, Constness::Const),
-                    abi,
+                    ext,
                 };
                 return self.parse_item_fn(lo, vis, attrs, header);
             }
@@ -193,7 +193,7 @@ impl<'a> Parser<'a> {
                     unsafety,
                     asyncness,
                     constness: respan(fn_span, Constness::NotConst),
-                    abi: Abi::new(sym::Rust, fn_span),
+                    ext: Extern::None,
                 };
                 return self.parse_item_fn(lo, vis, attrs, header);
             }
@@ -230,7 +230,7 @@ impl<'a> Parser<'a> {
                 unsafety: Unsafety::Normal,
                 asyncness: respan(fn_span, IsAsync::NotAsync),
                 constness: respan(fn_span, Constness::NotConst),
-                abi: Abi::new(sym::Rust, fn_span),
+                ext: Extern::None,
             };
             return self.parse_item_fn(lo, vis, attrs, header);
         }
@@ -242,14 +242,14 @@ impl<'a> Parser<'a> {
             self.bump(); // `unsafe`
             // `{` is also expected after `unsafe`; in case of error, include it in the diagnostic.
             self.check(&token::OpenDelim(token::Brace));
-            let abi = self.parse_extern_abi()?;
+            let ext = self.parse_extern()?;
             self.expect_keyword(kw::Fn)?;
             let fn_span = self.prev_span;
             let header = FnHeader {
                 unsafety: Unsafety::Unsafe,
                 asyncness: respan(fn_span, IsAsync::NotAsync),
                 constness: respan(fn_span, Constness::NotConst),
-                abi,
+                ext,
             };
             return self.parse_item_fn(lo, vis, attrs, header);
         }
@@ -1100,7 +1100,7 @@ impl<'a> Parser<'a> {
     fn parse_item_foreign_mod(
         &mut self,
         lo: Span,
-        abi: Abi,
+        abi: Option<StrLit>,
         visibility: Visibility,
         mut attrs: Vec<Attribute>,
         extern_sp: Span,
@@ -1775,9 +1775,16 @@ impl<'a> Parser<'a> {
         attrs: Vec<Attribute>,
         header: FnHeader,
     ) -> PResult<'a, Option<P<Item>>> {
+        let is_c_abi = match header.ext {
+            ast::Extern::None => false,
+            ast::Extern::Implicit => true,
+            ast::Extern::Explicit(abi) => abi.symbol_unescaped == sym::C,
+        };
         let (ident, decl, generics) = self.parse_fn_sig(ParamCfg {
             is_self_allowed: false,
-            allow_c_variadic: header.abi.symbol == sym::C && header.unsafety == Unsafety::Unsafe,
+            // FIXME: Parsing should not depend on ABI or unsafety and
+            // the variadic parameter should always be parsed.
+            allow_c_variadic: is_c_abi && header.unsafety == Unsafety::Unsafe,
             is_name_required: |_| true,
         })?;
         let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
@@ -1905,19 +1912,19 @@ impl<'a> Parser<'a> {
         }
         let asyncness = respan(self.prev_span, asyncness);
         let unsafety = self.parse_unsafety();
-        let (constness, unsafety, abi) = if is_const_fn {
-            (respan(const_span, Constness::Const), unsafety, Abi::default())
+        let (constness, unsafety, ext) = if is_const_fn {
+            (respan(const_span, Constness::Const), unsafety, Extern::None)
         } else {
-            let abi = self.parse_extern_abi()?;
-            (respan(self.prev_span, Constness::NotConst), unsafety, abi)
+            let ext = self.parse_extern()?;
+            (respan(self.prev_span, Constness::NotConst), unsafety, ext)
         };
         if !self.eat_keyword(kw::Fn) {
             // It is possible for `expect_one_of` to recover given the contents of
             // `self.expected_tokens`, therefore, do not use `self.unexpected()` which doesn't
             // account for this.
             if !self.expect_one_of(&[], &[])? { unreachable!() }
         }
-        Ok(FnHeader { constness, unsafety, asyncness, abi })
+        Ok(FnHeader { constness, unsafety, asyncness, ext })
     }
 
     /// Parse the "signature", including the identifier, parameters, and generics of a function.

src/librustc_parse/parser/mod.rs

@@ -15,8 +15,8 @@ use crate::{Directory, DirectoryOwnership};
 use crate::lexer::UnmatchedBrace;
 
 use syntax::ast::{
-    self, Abi, DUMMY_NODE_ID, AttrStyle, Attribute, CrateSugar, Ident,
-    IsAsync, MacDelimiter, Mutability, StrStyle, Visibility, VisibilityKind, Unsafety,
+    self, DUMMY_NODE_ID, AttrStyle, Attribute, CrateSugar, Extern, Ident, StrLit,
+    IsAsync, MacDelimiter, Mutability, Visibility, VisibilityKind, Unsafety,
 };
 
 use syntax::print::pprust;
@@ -1212,40 +1212,34 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses `extern string_literal?`.
-    /// If `extern` is not found, the Rust ABI is used.
-    /// If `extern` is found and a `string_literal` does not follow, the C ABI is used.
-    fn parse_extern_abi(&mut self) -> PResult<'a, Abi> {
+    fn parse_extern(&mut self) -> PResult<'a, Extern> {
         Ok(if self.eat_keyword(kw::Extern) {
-            self.parse_opt_abi()?
+            Extern::from_abi(self.parse_abi())
         } else {
-            Abi::default()
+            Extern::None
         })
     }
 
     /// Parses a string literal as an ABI spec.
-    /// If one is not found, the "C" ABI is used.
-    fn parse_opt_abi(&mut self) -> PResult<'a, Abi> {
-        let span = if self.token.can_begin_literal_or_bool() {
-            let ast::Lit { span, kind, .. } = self.parse_lit()?;
-            match kind {
-                ast::LitKind::Str(symbol, _) => return Ok(Abi::new(symbol, span)),
-                ast::LitKind::Err(_) => {}
+    fn parse_abi(&mut self) -> Option<StrLit> {
+        match self.parse_str_lit() {
+            Ok(str_lit) => Some(str_lit),
+            Err(Some(lit)) => match lit.kind {
+                ast::LitKind::Err(_) => None,
                 _ => {
-                    self.struct_span_err(span, "non-string ABI literal")
+                    self.struct_span_err(lit.span, "non-string ABI literal")
                         .span_suggestion(
-                            span,
+                            lit.span,
                             "specify the ABI with a string literal",
                             "\"C\"".to_string(),
                             Applicability::MaybeIncorrect,
                         )
                         .emit();
+                    None
                 }
             }
-            span
-        } else {
-            self.prev_span
-        };
-        Ok(Abi::new(sym::C, span))
+            Err(None) => None,
+        }
     }
 
     /// We are parsing `async fn`. If we are on Rust 2015, emit an error.
@@ -1337,34 +1331,6 @@ impl<'a> Parser<'a> {
             self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace) ||
                                    *t == token::BinOp(token::Star))
     }
-
-    fn parse_optional_str(&mut self) -> Option<(Symbol, ast::StrStyle, Option<ast::Name>)> {
-        let ret = match self.token.kind {
-            token::Literal(token::Lit { kind: token::Str, symbol, suffix }) =>
-                (symbol, ast::StrStyle::Cooked, suffix),
-            token::Literal(token::Lit { kind: token::StrRaw(n), symbol, suffix }) =>
-                (symbol, ast::StrStyle::Raw(n), suffix),
-            _ => return None
-        };
-        self.bump();
-        Some(ret)
-    }
-
-    pub fn parse_str(&mut self) -> PResult<'a, (Symbol, StrStyle)> {
-        match self.parse_optional_str() {
-            Some((s, style, suf)) => {
-                let sp = self.prev_span;
-                self.expect_no_suffix(sp, "a string literal", suf);
-                Ok((s, style))
-            }
-            _ => {
-                let msg = "expected string literal";
-                let mut err = self.fatal(msg);
-                err.span_label(self.token.span, msg);
-                Err(err)
-            }
-        }
-    }
 }
 
 crate fn make_unclosed_delims_error(

src/librustc_parse/parser/ty.rs

@@ -287,7 +287,7 @@ impl<'a> Parser<'a> {
         */
 
         let unsafety = self.parse_unsafety();
-        let abi = self.parse_extern_abi()?;
+        let ext = self.parse_extern()?;
         self.expect_keyword(kw::Fn)?;
         let cfg = ParamCfg {
             is_self_allowed: false,
@@ -296,7 +296,7 @@ impl<'a> Parser<'a> {
         };
         let decl = self.parse_fn_decl(cfg, false)?;
         Ok(TyKind::BareFn(P(BareFnTy {
-            abi,
+            ext,
             unsafety,
             generic_params,
             decl,