Rollup merge of #65884 - Centril:non-hardcoded-abis, r=petrochenkov

syntax: ABI-oblivious grammar

This PR has the following effects:

1. `extern $lit` is now legal where `$lit:literal` and `$lit` is substituted for a string literal.

2. `extern "abi_that_does_not_exist"` is now *syntactically* legal whereas before, the set of ABI strings was hard-coded into the grammar of the language. With this PR, the set of ABIs are instead validated and translated during lowering. That seems more appropriate.

3. `ast::FloatTy` is now distinct from `rustc_target::abi::FloatTy`. The former is used substantially more and the translation between them is only necessary in a single place.

4. As a result of 2-3, libsyntax no longer depends on librustc_target, which should improve pipe-lining somewhat.

cc @rust-lang/lang -- the points 1-2 slightly change the definition of the language but in a way which seems consistent with our general principles (in particular wrt. the discussions of turning things into semantic errors). I expect this to be uncontroversial but it's worth letting y'all know. :)

r? @varkor

2 files changed, 18 insertions, 16 deletions

diff --git a/src/libsyntax_ext/concat.rs b/src/libsyntax_ext/concat.rs
index 47bade698a8..4bf13f37711 100644
--- a/src/libsyntax_ext/concat.rs
+++ b/src/libsyntax_ext/concat.rs
@@ -21,8 +21,7 @@ pub fn expand_concat(
         match e.kind {
             ast::ExprKind::Lit(ref lit) => match lit.kind {
                 ast::LitKind::Str(ref s, _)
-                | ast::LitKind::Float(ref s, _)
-                | ast::LitKind::FloatUnsuffixed(ref s) => {
+                | ast::LitKind::Float(ref s, _) => {
                     accumulator.push_str(&s.as_str());
                 }
                 ast::LitKind::Char(c) => {
diff --git a/src/libsyntax_ext/deriving/generic/mod.rs b/src/libsyntax_ext/deriving/generic/mod.rs
index 2e5ae235893..b18fd50ae76 100644
--- a/src/libsyntax_ext/deriving/generic/mod.rs
+++ b/src/libsyntax_ext/deriving/generic/mod.rs
@@ -182,8 +182,7 @@ use std::iter;
 use std::vec;
 
 use rustc_data_structures::thin_vec::ThinVec;
-use rustc_target::spec::abi::Abi;
-use syntax::ast::{self, BinOpKind, EnumDef, Expr, Generics, Ident, PatKind};
+use syntax::ast::{self, Abi, BinOpKind, EnumDef, Expr, Generics, Ident, PatKind};
 use syntax::ast::{VariantData, GenericParamKind, GenericArg};
 use syntax::attr;
 use syntax::source_map::respan;
@@ -738,7 +737,7 @@ impl<'a> TraitDef<'a> {
                                          self,
                                          type_ident,
                                          generics,
-                                         Abi::Rust,
+                                         sym::Rust,
                                          explicit_self,
                                          tys,
                                          body)
@@ -793,7 +792,7 @@ impl<'a> TraitDef<'a> {
                                          self,
                                          type_ident,
                                          generics,
-                                         Abi::Rust,
+                                         sym::Rust,
                                          explicit_self,
                                          tys,
                                          body)
@@ -919,7 +918,7 @@ impl<'a> MethodDef<'a> {
                      trait_: &TraitDef<'_>,
                      type_ident: Ident,
                      generics: &Generics,
-                     abi: Abi,
+                     abi: Symbol,
                      explicit_self: Option<ast::ExplicitSelf>,
                      arg_types: Vec<(Ident, P<ast::Ty>)>,
                      body: P<Expr>)
@@ -949,23 +948,27 @@ impl<'a> MethodDef<'a> {
             ast::Unsafety::Normal
         };
 
+        let trait_lo_sp = trait_.span.shrink_to_lo();
+
+        let sig = ast::MethodSig {
+            header: ast::FnHeader {
+                unsafety,
+                abi: Abi::new(abi, trait_lo_sp),
+                ..ast::FnHeader::default()
+            },
+            decl: fn_decl,
+        };
+
         // Create the method.
         ast::ImplItem {
             id: ast::DUMMY_NODE_ID,
             attrs: self.attributes.clone(),
             generics: fn_generics,
             span: trait_.span,
-            vis: respan(trait_.span.shrink_to_lo(), ast::VisibilityKind::Inherited),
+            vis: respan(trait_lo_sp, ast::VisibilityKind::Inherited),
             defaultness: ast::Defaultness::Final,
             ident: method_ident,
-            kind: ast::ImplItemKind::Method(ast::MethodSig {
-                                                header: ast::FnHeader {
-                                                    unsafety, abi,
-                                                    ..ast::FnHeader::default()
-                                                },
-                                                decl: fn_decl,
-                                            },
-                                            body_block),
+            kind: ast::ImplItemKind::Method(sig, body_block),
             tokens: None,
         }
     }