Rollup merge of rust-lang#36868 - petrochenkov:adtstab, r=nikomatsakis

Partially stabilize RFC 1506 "Clarify relationships between ADTs"

Lifted restrictions on tuple structs/variants are stabilized, i.e. `S{..}` can be used with any structs and empty tuple structs are permitted without feature gate.
Numeric fields in struct expressions/patterns `S { 0: a, 1: b }` are **NOT** stabilized.
This was implemented 1.5 months ago in Rust 1.12, but this is a tiny technical change that could probably go even without RFC/stabilization period.

cc rust-lang#35626 rust-lang#36871
r? @nikomatsakis

Author: eddyb

src/librustc_typeck/check/mod.rs

@@ -3261,13 +3261,6 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         };
 
         if let Some((variant, did, substs)) = variant {
-            if variant.ctor_kind == CtorKind::Fn &&
-                    !self.tcx.sess.features.borrow().relaxed_adts {
-                emit_feature_err(&self.tcx.sess.parse_sess,
-                                 "relaxed_adts", path.span, GateIssue::Language,
-                                 "tuple structs and variants in struct patterns are unstable");
-            }
-
             // Check bounds on type arguments used in the path.
             let type_predicates = self.tcx.lookup_predicates(did);
             let bounds = self.instantiate_bounds(path.span, substs, &type_predicates);

src/libsyntax/feature_gate.rs

@@ -271,7 +271,6 @@ declare_features! (
     // Allows `impl Trait` in function return types.
     (active, conservative_impl_trait, "1.12.0", Some(34511)),
 
-    // Allows tuple structs and variants in more contexts,
     // Permits numeric fields in struct expressions and patterns.
     (active, relaxed_adts, "1.12.0", Some(35626)),
 
@@ -996,6 +995,10 @@ fn contains_novel_literal(item: &ast::MetaItem) -> bool {
     }
 }
 
+fn starts_with_digit(s: &str) -> bool {
+    s.as_bytes().first().cloned().map_or(false, |b| b >= b'0' && b <= b'9')
+}
+
 impl<'a> Visitor for PostExpansionVisitor<'a> {
     fn visit_attribute(&mut self, attr: &ast::Attribute) {
         if !self.context.cm.span_allows_unstable(attr.span) {
@@ -1175,6 +1178,11 @@ impl<'a> Visitor for PostExpansionVisitor<'a> {
                         gate_feature_post!(&self, field_init_shorthand, field.span,
                                            "struct field shorthands are unstable");
                     }
+                    if starts_with_digit(&field.ident.node.name.as_str()) {
+                        gate_feature_post!(&self, relaxed_adts,
+                                          field.span,
+                                          "numeric fields in struct expressions are unstable");
+                    }
                 }
             }
             _ => {}
@@ -1201,10 +1209,14 @@ impl<'a> Visitor for PostExpansionVisitor<'a> {
                                   pattern.span,
                                   "box pattern syntax is experimental");
             }
-            PatKind::TupleStruct(_, ref fields, ddpos)
-                    if ddpos.is_none() && fields.is_empty() => {
-                gate_feature_post!(&self, relaxed_adts, pattern.span,
-                                   "empty tuple structs patterns are unstable");
+            PatKind::Struct(_, ref fields, _) => {
+                for field in fields {
+                    if starts_with_digit(&field.node.ident.name.as_str()) {
+                        gate_feature_post!(&self, relaxed_adts,
+                                          field.span,
+                                          "numeric fields in struct patterns are unstable");
+                    }
+                }
             }
             _ => {}
         }
@@ -1287,19 +1299,6 @@ impl<'a> Visitor for PostExpansionVisitor<'a> {
         visit::walk_impl_item(self, ii);
     }
 
-    fn visit_variant_data(&mut self, vdata: &ast::VariantData, _: ast::Ident,
-                          _: &ast::Generics, _: NodeId, span: Span) {
-        if vdata.fields().is_empty() {
-            if vdata.is_tuple() {
-                gate_feature_post!(&self, relaxed_adts, span,
-                                   "empty tuple structs and enum variants are unstable, \
-                                    use unit structs and enum variants instead");
-            }
-        }
-
-        visit::walk_struct_def(self, vdata)
-    }
-
     fn visit_vis(&mut self, vis: &ast::Visibility) {
         let span = match *vis {
             ast::Visibility::Crate(span) => span,

src/test/compile-fail/auxiliary/empty-struct.rs

@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(relaxed_adts)]
-
 pub struct XEmpty1 {}
 pub struct XEmpty2;
 pub struct XEmpty6();

src/test/compile-fail/auxiliary/namespace-mix-new.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(item_like_imports, relaxed_adts)]
+#![feature(item_like_imports)]
 
 pub mod c {
     pub struct S {}

src/test/compile-fail/auxiliary/namespace-mix-old.rs

@@ -10,8 +10,6 @@
 
 // FIXME: Remove when `item_like_imports` is stabilized.
 
-#![feature(relaxed_adts)]
-
 pub mod c {
     pub struct S {}
     pub struct TS();

src/test/compile-fail/empty-struct-braces-pat-2.rs

@@ -12,8 +12,6 @@
 
 // aux-build:empty-struct.rs
 
-#![feature(relaxed_adts)]
-
 extern crate empty_struct;
 use empty_struct::*;
 

src/test/compile-fail/empty-struct-braces-pat-3.rs

@@ -12,8 +12,6 @@
 
 // aux-build:empty-struct.rs
 
-#![feature(relaxed_adts)]
-
 extern crate empty_struct;
 use empty_struct::*;
 

src/test/compile-fail/empty-struct-tuple-pat.rs

@@ -12,8 +12,6 @@
 
 // aux-build:empty-struct.rs
 
-#![feature(relaxed_adts)]
-
 extern crate empty_struct;
 use empty_struct::*;
 

src/test/compile-fail/empty-struct-unit-pat.rs

@@ -12,8 +12,6 @@
 
 // aux-build:empty-struct.rs
 
-#![feature(relaxed_adts)]
-
 extern crate empty_struct;
 use empty_struct::*;
 

src/test/compile-fail/feature-gate-relaxed-adts-2.rs

@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(relaxed_adts)]
-
 enum MyOption<T> {
     MySome(T),
     MyNone,

src/test/compile-fail/issue-16819.rs

@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(relaxed_adts)]
-
 struct NonCopyable(());
 
 fn main() {

src/test/compile-fail/issue-17800.rs

@@ -10,7 +10,7 @@
 
 // aux-build:namespace-mix-new.rs
 
-#![feature(item_like_imports, relaxed_adts)]
+#![feature(item_like_imports)]
 
 extern crate namespace_mix_new;
 use namespace_mix_new::*;

src/test/compile-fail/issue-4736.rs

@@ -12,8 +12,6 @@
 
 // aux-build:namespace-mix-old.rs
 
-#![feature(relaxed_adts)]
-
 extern crate namespace_mix_old;
 use namespace_mix_old::{xm1, xm2, xm3, xm4, xm5, xm6, xm7, xm8, xm9, xmA, xmB, xmC};
 

src/test/compile-fail/namespace-mix-new.rs

@@ -8,19 +8,11 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-struct S(); //~ ERROR empty tuple structs and enum variants are unstable
-struct Z(u8, u8);
-
-enum E {
-    V(), //~ ERROR empty tuple structs and enum variants are unstable
-    U(u8, u8),
-}
+struct S(u8);
 
 fn main() {
-    match S() {
-        S() => {} //~ ERROR empty tuple structs patterns are unstable
-    }
-    match E::V() {
-        E::V() => {} //~ ERROR empty tuple structs patterns are unstable
+    let s = S{0: 10}; //~ ERROR numeric fields in struct expressions are unstable
+    match s {
+        S{0: a, ..} => {} //~ ERROR numeric fields in struct patterns are unstable
     }
 }

src/test/compile-fail/namespace-mix-old.rs

@@ -10,7 +10,6 @@
 
 // `#[derive(Trait)]` works for empty structs/variants with braces or parens.
 
-#![feature(relaxed_adts)]
 #![feature(rustc_private)]
 
 extern crate serialize as rustc_serialize;

src/test/compile-fail/feature-gate-relaxed-adts.rs renamed to src/test/compile-fail/numeric-fields-feature-gate.rs

@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(relaxed_adts)]
-
 pub struct XEmpty1 {}
 pub struct XEmpty2;
 pub struct XEmpty7();

src/test/run-pass-fulldeps/empty-struct-braces-derive.rs

@@ -13,8 +13,6 @@
 
 // aux-build:empty-struct.rs
 
-#![feature(relaxed_adts)]
-
 extern crate empty_struct;
 use empty_struct::*;