Auto merge of #54271 - petrochenkov:nolegder, r=eddyb,alexcrichton

Unsupport `#[derive(Trait)]` sugar for `#[derive_Trait]` legacy plugin attributes

This is a long deprecated unstable feature that doesn't mesh well with regular resolution/expansion.

How to fix broken code:
- The recommended way is to migrate to stable procedural macros - derives or attributes (https://doc.rust-lang.org/nightly/book/first-edition/procedural-macros.html).
- If that's not possible right now for some reason, you can keep code working with a simple mechanical replacement `#[derive(Legacy)]` -> `#[derive_Legacy]`.

Closes #29644

r? @ghost

Author: bors

src/librustc_driver/driver.rs

@@ -908,7 +908,6 @@ where
         }
     });
 
-    let whitelisted_legacy_custom_derives = registry.take_whitelisted_custom_derives();
     let Registry {
         syntax_exts,
         early_lint_passes,
@@ -955,7 +954,6 @@ where
         crate_loader,
         &resolver_arenas,
     );
-    resolver.whitelisted_legacy_custom_derives = whitelisted_legacy_custom_derives;
     syntax_ext::register_builtins(&mut resolver, syntax_exts, sess.features_untracked().quote);
 
     // Expand all macros

src/librustc_plugin/registry.rs

@@ -60,8 +60,6 @@ pub struct Registry<'a> {
 
     #[doc(hidden)]
     pub attributes: Vec<(String, AttributeType)>,
-
-    whitelisted_custom_derives: Vec<ast::Name>,
 }
 
 impl<'a> Registry<'a> {
@@ -77,7 +75,6 @@ impl<'a> Registry<'a> {
             lint_groups: FxHashMap::default(),
             llvm_passes: vec![],
             attributes: vec![],
-            whitelisted_custom_derives: Vec::new(),
         }
     }
 
@@ -130,19 +127,6 @@ impl<'a> Registry<'a> {
         }));
     }
 
-    /// This can be used in place of `register_syntax_extension` to register legacy custom derives
-    /// (i.e. attribute syntax extensions whose name begins with `derive_`). Legacy custom
-    /// derives defined by this function do not trigger deprecation warnings when used.
-    pub fn register_custom_derive(&mut self, name: ast::Name, extension: SyntaxExtension) {
-        assert!(name.as_str().starts_with("derive_"));
-        self.whitelisted_custom_derives.push(name);
-        self.register_syntax_extension(name, extension);
-    }
-
-    pub fn take_whitelisted_custom_derives(&mut self) -> Vec<ast::Name> {
-        ::std::mem::replace(&mut self.whitelisted_custom_derives, Vec::new())
-    }
-
     /// Register a macro of the usual kind.
     ///
     /// This is a convenience wrapper for `register_syntax_extension`.

src/librustc_resolve/lib.rs

@@ -1588,7 +1588,6 @@ pub struct Resolver<'a, 'b: 'a> {
     macro_map: FxHashMap<DefId, Lrc<SyntaxExtension>>,
     macro_defs: FxHashMap<Mark, DefId>,
     local_macro_def_scopes: FxHashMap<NodeId, Module<'a>>,
-    pub whitelisted_legacy_custom_derives: Vec<Name>,
     pub found_unresolved_macro: bool,
 
     /// List of crate local macros that we need to warn about as being unused.
@@ -1922,7 +1921,6 @@ impl<'a, 'crateloader: 'a> Resolver<'a, 'crateloader> {
             macro_defs,
             local_macro_def_scopes: FxHashMap::default(),
             name_already_seen: FxHashMap::default(),
-            whitelisted_legacy_custom_derives: Vec::new(),
             potentially_unused_imports: Vec::new(),
             struct_constructors: Default::default(),
             found_unresolved_macro: false,

src/librustc_resolve/macros.rs

@@ -21,22 +21,18 @@ use rustc::hir::def_id::{DefId, CRATE_DEF_INDEX, DefIndex,
 use rustc::hir::def::{Def, NonMacroAttrKind};
 use rustc::hir::map::{self, DefCollector};
 use rustc::{ty, lint};
-use syntax::ast::{self, Name, Ident};
+use syntax::ast::{self, Ident};
 use syntax::attr;
 use syntax::errors::DiagnosticBuilder;
 use syntax::ext::base::{self, Determinacy};
-use syntax::ext::base::{MacroKind, SyntaxExtension, Resolver as SyntaxResolver};
+use syntax::ext::base::{MacroKind, SyntaxExtension};
 use syntax::ext::expand::{AstFragment, Invocation, InvocationKind};
 use syntax::ext::hygiene::{self, Mark};
 use syntax::ext::tt::macro_rules;
-use syntax::feature_gate::{self, feature_err, emit_feature_err, is_builtin_attr_name, GateIssue};
-use syntax::feature_gate::EXPLAIN_DERIVE_UNDERSCORE;
+use syntax::feature_gate::{feature_err, is_builtin_attr_name, GateIssue};
 use syntax::fold::{self, Folder};
-use syntax::parse::parser::PathStyle;
-use syntax::parse::token::{self, Token};
 use syntax::ptr::P;
 use syntax::symbol::{Symbol, keywords};
-use syntax::tokenstream::{TokenStream, TokenTree, Delimited, DelimSpan};
 use syntax::util::lev_distance::find_best_match_for_name;
 use syntax_pos::{Span, DUMMY_SP};
 use errors::Applicability;
@@ -194,10 +190,6 @@ impl<'a, 'crateloader: 'a> base::Resolver for Resolver<'a, 'crateloader> {
         ret.into_iter().next().unwrap()
     }
 
-    fn is_whitelisted_legacy_custom_derive(&self, name: Name) -> bool {
-        self.whitelisted_legacy_custom_derives.contains(&name)
-    }
-
     fn visit_ast_fragment_with_placeholders(&mut self, mark: Mark, fragment: &AstFragment,
                                             derives: &[Mark]) {
         let invocation = self.invocations[&mark];
@@ -240,79 +232,6 @@ impl<'a, 'crateloader: 'a> base::Resolver for Resolver<'a, 'crateloader> {
         ImportResolver { resolver: self }.resolve_imports()
     }
 
-    // Resolves attribute and derive legacy macros from `#![plugin(..)]`.
-    fn find_legacy_attr_invoc(&mut self, attrs: &mut Vec<ast::Attribute>, allow_derive: bool)
-                              -> Option<ast::Attribute> {
-        if !allow_derive {
-            return None;
-        }
-
-        // Check for legacy derives
-        for i in 0..attrs.len() {
-            let name = attrs[i].name();
-
-            if name == "derive" {
-                let result = attrs[i].parse_list(&self.session.parse_sess, |parser| {
-                    parser.parse_path_allowing_meta(PathStyle::Mod)
-                });
-
-                let mut traits = match result {
-                    Ok(traits) => traits,
-                    Err(mut e) => {
-                        e.cancel();
-                        continue
-                    }
-                };
-
-                for j in 0..traits.len() {
-                    if traits[j].segments.len() > 1 {
-                        continue
-                    }
-                    let trait_name = traits[j].segments[0].ident.name;
-                    let legacy_name = Symbol::intern(&format!("derive_{}", trait_name));
-                    if !self.builtin_macros.contains_key(&legacy_name) {
-                        continue
-                    }
-                    let span = traits.remove(j).span;
-                    self.gate_legacy_custom_derive(legacy_name, span);
-                    if traits.is_empty() {
-                        attrs.remove(i);
-                    } else {
-                        let mut tokens = Vec::with_capacity(traits.len() - 1);
-                        for (j, path) in traits.iter().enumerate() {
-                            if j > 0 {
-                                tokens.push(TokenTree::Token(attrs[i].span, Token::Comma).into());
-                            }
-                            tokens.reserve((path.segments.len() * 2).saturating_sub(1));
-                            for (k, segment) in path.segments.iter().enumerate() {
-                                if k > 0 {
-                                    tokens.push(TokenTree::Token(path.span, Token::ModSep).into());
-                                }
-                                let tok = Token::from_ast_ident(segment.ident);
-                                tokens.push(TokenTree::Token(path.span, tok).into());
-                            }
-                        }
-                        let delim_span = DelimSpan::from_single(attrs[i].span);
-                        attrs[i].tokens = TokenTree::Delimited(delim_span, Delimited {
-                            delim: token::Paren,
-                            tts: TokenStream::concat(tokens).into(),
-                        }).into();
-                    }
-                    return Some(ast::Attribute {
-                        path: ast::Path::from_ident(Ident::new(legacy_name, span)),
-                        tokens: TokenStream::empty(),
-                        id: attr::mk_attr_id(),
-                        style: ast::AttrStyle::Outer,
-                        is_sugared_doc: false,
-                        span,
-                    });
-                }
-            }
-        }
-
-        None
-    }
-
     fn resolve_macro_invocation(&mut self, invoc: &Invocation, invoc_id: Mark, force: bool)
                                 -> Result<Option<Lrc<SyntaxExtension>>, Determinacy> {
         let (path, kind, derives_in_scope, after_derive) = match invoc.kind {
@@ -430,11 +349,6 @@ impl<'a, 'cl> Resolver<'a, 'cl> {
                                 feature_err(&self.session.parse_sess, "rustc_attrs", path.span,
                                             GateIssue::Language, &msg).emit();
                             }
-                        } else if name.starts_with("derive_") {
-                            if !features.custom_derive {
-                                feature_err(&self.session.parse_sess, "custom_derive", path.span,
-                                            GateIssue::Language, EXPLAIN_DERIVE_UNDERSCORE).emit();
-                            }
                         } else if !features.custom_attribute {
                             let msg = format!("The attribute `{}` is currently unknown to the \
                                                compiler and may have meaning added to it in the \
@@ -1218,14 +1132,4 @@ impl<'a, 'cl> Resolver<'a, 'cl> {
             self.define(module, ident, MacroNS, (def, vis, item.span, expansion));
         }
     }
-
-    fn gate_legacy_custom_derive(&mut self, name: Symbol, span: Span) {
-        if !self.session.features_untracked().custom_derive {
-            let sess = &self.session.parse_sess;
-            let explain = feature_gate::EXPLAIN_CUSTOM_DERIVE;
-            emit_feature_err(sess, "custom_derive", span, GateIssue::Language, explain);
-        } else if !self.is_whitelisted_legacy_custom_derive(name) {
-            self.session.span_warn(span, feature_gate::EXPLAIN_DEPR_CUSTOM_DERIVE);
-        }
-    }
 }

src/libsyntax/ext/base.rs

@@ -733,16 +733,12 @@ pub trait Resolver {
     fn next_node_id(&mut self) -> ast::NodeId;
     fn get_module_scope(&mut self, id: ast::NodeId) -> Mark;
     fn eliminate_crate_var(&mut self, item: P<ast::Item>) -> P<ast::Item>;
-    fn is_whitelisted_legacy_custom_derive(&self, name: Name) -> bool;
 
     fn visit_ast_fragment_with_placeholders(&mut self, mark: Mark, fragment: &AstFragment,
                                             derives: &[Mark]);
     fn add_builtin(&mut self, ident: ast::Ident, ext: Lrc<SyntaxExtension>);
 
     fn resolve_imports(&mut self);
-    // Resolves attribute and derive legacy macros from `#![plugin(..)]`.
-    fn find_legacy_attr_invoc(&mut self, attrs: &mut Vec<Attribute>, allow_derive: bool)
-                              -> Option<Attribute>;
 
     fn resolve_macro_invocation(&mut self, invoc: &Invocation, invoc_id: Mark, force: bool)
                                 -> Result<Option<Lrc<SyntaxExtension>>, Determinacy>;
@@ -771,15 +767,12 @@ impl Resolver for DummyResolver {
     fn next_node_id(&mut self) -> ast::NodeId { ast::DUMMY_NODE_ID }
     fn get_module_scope(&mut self, _id: ast::NodeId) -> Mark { Mark::root() }
     fn eliminate_crate_var(&mut self, item: P<ast::Item>) -> P<ast::Item> { item }
-    fn is_whitelisted_legacy_custom_derive(&self, _name: Name) -> bool { false }
 
     fn visit_ast_fragment_with_placeholders(&mut self, _invoc: Mark, _fragment: &AstFragment,
                                             _derives: &[Mark]) {}
     fn add_builtin(&mut self, _ident: ast::Ident, _ext: Lrc<SyntaxExtension>) {}
 
     fn resolve_imports(&mut self) {}
-    fn find_legacy_attr_invoc(&mut self, _attrs: &mut Vec<Attribute>, _allow_derive: bool)
-                              -> Option<Attribute> { None }
     fn resolve_macro_invocation(&mut self, _invoc: &Invocation, _invoc_id: Mark, _force: bool)
                                 -> Result<Option<Lrc<SyntaxExtension>>, Determinacy> {
         Err(Determinacy::Determined)

src/libsyntax/ext/expand.rs

@@ -1134,12 +1134,6 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
         let (mut attr, mut traits, mut after_derive) = (None, Vec::new(), false);
 
         item = item.map_attrs(|mut attrs| {
-            if let Some(legacy_attr_invoc) = self.cx.resolver.find_legacy_attr_invoc(&mut attrs,
-                                                                                     true) {
-                attr = Some(legacy_attr_invoc);
-                return attrs;
-            }
-
             attr = self.find_attr_invoc(&mut attrs, &mut after_derive);
             traits = collect_derives(&mut self.cx, &mut attrs);
             attrs
@@ -1156,12 +1150,6 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
         let (mut attr, mut after_derive) = (None, false);
 
         item = item.map_attrs(|mut attrs| {
-            if let Some(legacy_attr_invoc) = self.cx.resolver.find_legacy_attr_invoc(&mut attrs,
-                                                                                     false) {
-                attr = Some(legacy_attr_invoc);
-                return attrs;
-            }
-
             attr = self.find_attr_invoc(&mut attrs, &mut after_derive);
             attrs
         });
@@ -1623,15 +1611,13 @@ impl<'feat> ExpansionConfig<'feat> {
     }
 
     feature_tests! {
-        fn enable_quotes = quote,
         fn enable_asm = asm,
         fn enable_custom_test_frameworks = custom_test_frameworks,
         fn enable_global_asm = global_asm,
         fn enable_log_syntax = log_syntax,
         fn enable_concat_idents = concat_idents,
         fn enable_trace_macros = trace_macros,
         fn enable_allow_internal_unstable = allow_internal_unstable,
-        fn enable_custom_derive = custom_derive,
         fn enable_format_args_nl = format_args_nl,
         fn macros_in_extern_enabled = macros_in_extern,
         fn proc_macro_hygiene = proc_macro_hygiene,

src/libsyntax/feature_gate.rs

@@ -176,10 +176,6 @@ declare_features! (
     // Allows the use of custom attributes; RFC 572
     (active, custom_attribute, "1.0.0", Some(29642), None),
 
-    // Allows the use of #[derive(Anything)] as sugar for
-    // #[derive_Anything].
-    (active, custom_derive, "1.0.0", Some(29644), None),
-
     // Allows the use of rustc_* attributes; RFC 572
     (active, rustc_attrs, "1.0.0", Some(29642), None),
 
@@ -530,6 +526,9 @@ declare_features! (
      Some("subsumed by `#![feature(proc_macro_hygiene)]`")),
     (removed, panic_implementation, "1.28.0", Some(44489), None,
      Some("subsumed by `#[panic_handler]`")),
+    // Allows the use of `#[derive(Anything)]` as sugar for `#[derive_Anything]`.
+    (removed, custom_derive, "1.0.0", Some(29644), None,
+     Some("subsumed by `#[proc_macro_derive]`")),
 );
 
 declare_features! (
@@ -1287,8 +1286,6 @@ impl<'a> Context<'a> {
                           "unless otherwise specified, attributes \
                            with the prefix `rustc_` \
                            are reserved for internal compiler diagnostics");
-        } else if name.starts_with("derive_") {
-            gate_feature!(self, custom_derive, attr.span, EXPLAIN_DERIVE_UNDERSCORE);
         } else if !attr::is_known(attr) {
             // Only run the custom attribute lint during regular
             // feature gate checking. Macro gating runs
@@ -1418,16 +1415,6 @@ pub const EXPLAIN_ALLOW_INTERNAL_UNSTABLE: &str =
 pub const EXPLAIN_ALLOW_INTERNAL_UNSAFE: &str =
     "allow_internal_unsafe side-steps the unsafe_code lint";
 
-pub const EXPLAIN_CUSTOM_DERIVE: &str =
-    "`#[derive]` for custom traits is deprecated and will be removed in the future.";
-
-pub const EXPLAIN_DEPR_CUSTOM_DERIVE: &str =
-    "`#[derive]` for custom traits is deprecated and will be removed in the future. \
-    Prefer using procedural macro custom derive.";
-
-pub const EXPLAIN_DERIVE_UNDERSCORE: &str =
-    "attributes of the form `#[derive_*]` are reserved for the compiler";
-
 pub const EXPLAIN_UNSIZED_TUPLE_COERCION: &str =
     "unsized tuple coercion is not stable enough for use and is subject to change";
 

src/libsyntax_ext/lib.rs

@@ -39,10 +39,6 @@ extern crate log;
 
 mod diagnostics;
 
-#[macro_use]
-// for custom_derive
-pub mod deriving;
-
 mod asm;
 mod assert;
 mod cfg;
@@ -54,13 +50,14 @@ mod format;
 mod format_foreign;
 mod global_asm;
 mod log_syntax;
-mod trace_macros;
+mod proc_macro_server;
 mod test;
 mod test_case;
+mod trace_macros;
 
+pub mod deriving;
 pub mod proc_macro_decls;
 pub mod proc_macro_impl;
-mod proc_macro_server;
 
 use rustc_data_structures::sync::Lrc;
 use syntax::ast;

src/test/compile-fail/proc-macro/derive-still-gated.rs

@@ -15,7 +15,7 @@
 #[macro_use]
 extern crate derive_a;
 
-#[derive_A] //~ ERROR: attributes of the form `#[derive_*]` are reserved for the compiler
+#[derive_A] //~ ERROR attribute `derive_A` is currently unknown
 struct A;
 
 fn main() {}

src/test/run-pass-fulldeps/auxiliary/custom_derive_plugin.rs

@@ -31,11 +31,11 @@ use rustc_plugin::Registry;
 
 #[plugin_registrar]
 pub fn plugin_registrar(reg: &mut Registry) {
-    reg.register_custom_derive(
+    reg.register_syntax_extension(
         Symbol::intern("derive_TotalSum"),
         MultiDecorator(box expand));
 
-    reg.register_custom_derive(
+    reg.register_syntax_extension(
         Symbol::intern("derive_Nothing"),
         MultiDecorator(box noop));
 }