Auto merge of rust-lang#51587 - mark-i-m:at_most_once_rep_2018, r=alexcrichton

2018 edition `?` Kleene operator

This is my first attempt at implementing the migration lint + 2018 behavior as discussed in rust-lang#48075

r? @nikomatsakis

Author: bors

src/doc/unstable-book/src/language-features/macro-at-most-once-rep.md

@@ -1,13 +1,15 @@
 # `macro_at_most_once_rep`
 
-The tracking issue for this feature is: TODO(mark-i-m)
+NOTE: This feature is only available in the 2018 Edition.
+
+The tracking issue for this feature is: #48075
 
 With this feature gate enabled, one can use `?` as a Kleene operator meaning "0
 or 1 repetitions" in a macro definition. Previously only `+` and `*` were allowed.
 
 For example:
 
-```rust
+```rust,ignore
 #![feature(macro_at_most_once_rep)]
 
 macro_rules! foo {

src/librustc/lint/builtin.rs

@@ -331,6 +331,15 @@ declare_lint! {
      via the module system"
 }
 
+/// Some lints that are buffered from `libsyntax`. See `syntax::early_buffered_lints`.
+pub mod parser {
+    declare_lint! {
+        pub QUESTION_MARK_MACRO_SEP,
+        Allow,
+        "detects the use of `?` as a macro separator"
+    }
+}
+
 /// Does nothing as a lint pass, but registers some `Lint`s
 /// which are used by other parts of the compiler.
 #[derive(Copy, Clone)]
@@ -389,6 +398,7 @@ impl LintPass for HardwiredLints {
             WHERE_CLAUSES_OBJECT_SAFETY,
             PROC_MACRO_DERIVE_RESOLUTION_FALLBACK,
             MACRO_USE_EXTERN_CRATE,
+            parser::QUESTION_MARK_MACRO_SEP,
         )
     }
 }

src/librustc/lint/mod.rs

@@ -38,10 +38,12 @@ use hir::def_id::{CrateNum, LOCAL_CRATE};
 use hir::intravisit;
 use hir;
 use lint::builtin::BuiltinLintDiagnostics;
+use lint::builtin::parser::QUESTION_MARK_MACRO_SEP;
 use session::{Session, DiagnosticMessageId};
 use std::{hash, ptr};
 use syntax::ast;
 use syntax::codemap::{MultiSpan, ExpnFormat};
+use syntax::early_buffered_lints::BufferedEarlyLintId;
 use syntax::edition::Edition;
 use syntax::symbol::Symbol;
 use syntax::visit as ast_visit;
@@ -86,6 +88,13 @@ pub struct Lint {
 }
 
 impl Lint {
+    /// Returns the `rust::lint::Lint` for a `syntax::early_buffered_lints::BufferedEarlyLintId`.
+    pub fn from_parser_lint_id(lint_id: BufferedEarlyLintId) -> &'static Self {
+        match lint_id {
+            BufferedEarlyLintId::QuestionMarkMacroSep => QUESTION_MARK_MACRO_SEP,
+        }
+    }
+
     /// Get the lint's name, with ASCII letters converted to lowercase.
     pub fn name_lower(&self) -> String {
         self.name.to_ascii_lowercase()
@@ -118,7 +127,7 @@ macro_rules! declare_lint {
         };
     );
     ($vis: vis $NAME: ident, $Level: ident, $desc: expr,
-     $lint_edition: expr => $edition_level: ident $(,)?
+     $lint_edition: expr => $edition_level: ident
     ) => (
         $vis static $NAME: &$crate::lint::Lint = &$crate::lint::Lint {
             name: stringify!($NAME),
@@ -133,7 +142,8 @@ macro_rules! declare_lint {
 /// Declare a static `LintArray` and return it as an expression.
 #[macro_export]
 macro_rules! lint_array {
-    ($( $lint:expr ),* $(,)?) => {{
+    ($( $lint:expr ),* ,) => { lint_array!( $($lint),* ) };
+    ($( $lint:expr ),*) => {{
         vec![$($lint),*]
     }}
 }

src/librustc/macros.rs

@@ -71,7 +71,9 @@ macro_rules! __impl_stable_hash_field {
 
 #[macro_export]
 macro_rules! impl_stable_hash_for {
-    (enum $enum_name:path { $( $variant:ident $( ( $($field:ident $(-> $delegate:tt)?),* ) )* ),* $(,)? }) => {
+    // FIXME(mark-i-m): Some of these should be `?` rather than `*`. See the git blame and change
+    // them back when `?` is supported again.
+    (enum $enum_name:path { $( $variant:ident $( ( $($field:ident $(-> $delegate:tt)*),* ) )* ),* $(,)* }) => {
         impl<'a, 'tcx> ::rustc_data_structures::stable_hasher::HashStable<$crate::ich::StableHashingContext<'a>> for $enum_name {
             #[inline]
             fn hash_stable<W: ::rustc_data_structures::stable_hasher::StableHasherResult>(&self,
@@ -83,14 +85,15 @@ macro_rules! impl_stable_hash_for {
                 match *self {
                     $(
                         $variant $( ( $(ref $field),* ) )* => {
-                            $($( __impl_stable_hash_field!($field, __ctx, __hasher $(, $delegate)?) );*)*
+                            $($( __impl_stable_hash_field!($field, __ctx, __hasher $(, $delegate)*) );*)*
                         }
                     )*
                 }
             }
         }
     };
-    (struct $struct_name:path { $($field:ident $(-> $delegate:tt)?),*  $(,)? }) => {
+    // FIXME(mark-i-m): same here.
+    (struct $struct_name:path { $($field:ident $(-> $delegate:tt)*),*  $(,)* }) => {
         impl<'a, 'tcx> ::rustc_data_structures::stable_hasher::HashStable<$crate::ich::StableHashingContext<'a>> for $struct_name {
             #[inline]
             fn hash_stable<W: ::rustc_data_structures::stable_hasher::StableHasherResult>(&self,
@@ -100,11 +103,12 @@ macro_rules! impl_stable_hash_for {
                     $(ref $field),*
                 } = *self;
 
-                $( __impl_stable_hash_field!($field, __ctx, __hasher $(, $delegate)?) );*
+                $( __impl_stable_hash_field!($field, __ctx, __hasher $(, $delegate)*) );*
             }
         }
     };
-    (tuple_struct $struct_name:path { $($field:ident $(-> $delegate:tt)?),*  $(,)? }) => {
+    // FIXME(mark-i-m): same here.
+    (tuple_struct $struct_name:path { $($field:ident $(-> $delegate:tt)*),*  $(,)* }) => {
         impl<'a, 'tcx> ::rustc_data_structures::stable_hasher::HashStable<$crate::ich::StableHashingContext<'a>> for $struct_name {
             #[inline]
             fn hash_stable<W: ::rustc_data_structures::stable_hasher::StableHasherResult>(&self,
@@ -114,7 +118,7 @@ macro_rules! impl_stable_hash_for {
                     $(ref $field),*
                 ) = *self;
 
-                $( __impl_stable_hash_field!($field, __ctx, __hasher $(, $delegate)?) );*
+                $( __impl_stable_hash_field!($field, __ctx, __hasher $(, $delegate)*) );*
             }
         }
     };

src/librustc_driver/driver.rs

@@ -52,6 +52,7 @@ use std::path::{Path, PathBuf};
 use rustc_data_structures::sync::{self, Lrc, Lock};
 use std::sync::mpsc;
 use syntax::{self, ast, attr, diagnostics, visit};
+use syntax::early_buffered_lints::BufferedEarlyLint;
 use syntax::ext::base::ExtCtxt;
 use syntax::fold::Folder;
 use syntax::parse::{self, PResult};
@@ -1066,6 +1067,15 @@ where
         )
     });
 
+    // Add all buffered lints from the `ParseSess` to the `Session`.
+    sess.parse_sess.buffered_lints.with_lock(|buffered_lints| {
+        info!("{} parse sess buffered_lints", buffered_lints.len());
+        for BufferedEarlyLint{id, span, msg, lint_id} in buffered_lints.drain(..) {
+            let lint = lint::Lint::from_parser_lint_id(lint_id);
+            sess.buffer_lint(lint, id, span, &msg);
+        }
+    });
+
     // Done with macro expansion!
 
     after_expand(&krate)?;

src/librustc_lint/builtin.rs

@@ -617,7 +617,7 @@ declare_lint! {
     pub ANONYMOUS_PARAMETERS,
     Allow,
     "detects anonymous parameters",
-    Edition::Edition2018 => Warn,
+    Edition::Edition2018 => Warn
 }
 
 /// Checks for use of anonymous parameters (RFC 1685)
@@ -1706,7 +1706,7 @@ impl LintPass for SoftLints {
             UNIONS_WITH_DROP_FIELDS,
             UNREACHABLE_PUB,
             TYPE_ALIAS_BOUNDS,
-            TRIVIAL_BOUNDS,
+            TRIVIAL_BOUNDS
         )
     }
 }

src/librustc_lint/lib.rs

@@ -44,9 +44,13 @@ extern crate syntax_pos;
 
 use rustc::lint;
 use rustc::lint::{LateContext, LateLintPass, LintPass, LintArray};
-use rustc::lint::builtin::{BARE_TRAIT_OBJECTS, ABSOLUTE_PATHS_NOT_STARTING_WITH_CRATE,
-                           ELIDED_LIFETIMES_IN_PATHS};
-use rustc::lint::builtin::MACRO_USE_EXTERN_CRATE;
+use rustc::lint::builtin::{
+    BARE_TRAIT_OBJECTS,
+    ABSOLUTE_PATHS_NOT_STARTING_WITH_CRATE,
+    MACRO_USE_EXTERN_CRATE,
+    ELIDED_LIFETIMES_IN_PATHS,
+    parser::QUESTION_MARK_MACRO_SEP
+};
 use rustc::session;
 use rustc::util;
 use rustc::hir;
@@ -321,6 +325,11 @@ pub fn register_builtins(store: &mut lint::LintStore, sess: Option<&Session>) {
             reference: "issue #50504 <https://github.com/rust-lang/rust/issues/50504>",
             edition: None,
         },
+        FutureIncompatibleInfo {
+            id: LintId::of(QUESTION_MARK_MACRO_SEP),
+            reference: "issue #48075 <https://github.com/rust-lang/rust/issues/48075>",
+            edition: Some(Edition::Edition2018),
+        }
         ]);
 
     // Register renamed and removed lints

src/libsyntax/early_buffered_lints.rs

@@ -0,0 +1,39 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Allows the buffering of lints for later.
+//!
+//! Since we cannot have a dependency on `librustc`, we implement some types here that are somewhat
+//! redundant. Later, these types can be converted to types for use by the rest of the compiler.
+
+use syntax::ast::NodeId;
+use syntax_pos::MultiSpan;
+
+/// Since we cannot import `LintId`s from `rustc::lint`, we define some Ids here which can later be
+/// passed to `rustc::lint::Lint::from_parser_lint_id` to get a `rustc::lint::Lint`.
+pub enum BufferedEarlyLintId {
+    /// Usage of `?` as a macro separator is deprecated.
+    QuestionMarkMacroSep,
+}
+
+/// Stores buffered lint info which can later be passed to `librustc`.
+pub struct BufferedEarlyLint {
+    /// The span of code that we are linting on.
+   pub span: MultiSpan,
+
+   /// The lint message.
+   pub msg: String,
+
+   /// The `NodeId` of the AST node that generated the lint.
+   pub id: NodeId,
+
+   /// A lint Id that can be passed to `rustc::lint::Lint::from_parser_lint_id`.
+   pub lint_id: BufferedEarlyLintId,
+}

src/libsyntax/ext/expand.rs

@@ -44,8 +44,10 @@ macro_rules! ast_fragments {
     (
         $($Kind:ident($AstTy:ty) {
             $kind_name:expr;
-            $(one fn $fold_ast:ident; fn $visit_ast:ident;)?
-            $(many fn $fold_ast_elt:ident; fn $visit_ast_elt:ident;)?
+            // FIXME: HACK: this should be `$(one ...)?` and `$(many ...)?` but `?` macro
+            // repetition was removed from 2015 edition in #51587 because of ambiguities.
+            $(one fn $fold_ast:ident; fn $visit_ast:ident;)*
+            $(many fn $fold_ast_elt:ident; fn $visit_ast_elt:ident;)*
             fn $make_ast:ident;
         })*
     ) => {
@@ -100,22 +102,22 @@ macro_rules! ast_fragments {
                     AstFragment::OptExpr(expr) =>
                         AstFragment::OptExpr(expr.and_then(|expr| folder.fold_opt_expr(expr))),
                     $($(AstFragment::$Kind(ast) =>
-                        AstFragment::$Kind(folder.$fold_ast(ast)),)?)*
+                        AstFragment::$Kind(folder.$fold_ast(ast)),)*)*
                     $($(AstFragment::$Kind(ast) =>
                         AstFragment::$Kind(ast.into_iter()
                                               .flat_map(|ast| folder.$fold_ast_elt(ast))
-                                              .collect()),)?)*
+                                              .collect()),)*)*
                 }
             }
 
             pub fn visit_with<'a, V: Visitor<'a>>(&'a self, visitor: &mut V) {
                 match *self {
                     AstFragment::OptExpr(Some(ref expr)) => visitor.visit_expr(expr),
                     AstFragment::OptExpr(None) => {}
-                    $($(AstFragment::$Kind(ref ast) => visitor.$visit_ast(ast),)?)*
+                    $($(AstFragment::$Kind(ref ast) => visitor.$visit_ast(ast),)*)*
                     $($(AstFragment::$Kind(ref ast) => for ast_elt in &ast[..] {
                         visitor.$visit_ast_elt(ast_elt);
-                    })?)*
+                    })*)*
                 }
             }
         }
@@ -126,10 +128,10 @@ macro_rules! ast_fragments {
             }
             $($(fn $fold_ast(&mut self, ast: $AstTy) -> $AstTy {
                 self.expand_fragment(AstFragment::$Kind(ast)).$make_ast()
-            })?)*
+            })*)*
             $($(fn $fold_ast_elt(&mut self, ast_elt: <$AstTy as IntoIterator>::Item) -> $AstTy {
                 self.expand_fragment(AstFragment::$Kind(SmallVector::one(ast_elt))).$make_ast()
-            })?)*
+            })*)*
         }
 
         impl<'a> MacResult for ::ext::tt::macro_rules::ParserAnyMacro<'a> {

src/libsyntax/ext/tt/macro_rules.rs

@@ -240,8 +240,17 @@ pub fn compile(sess: &ParseSess, features: &Features, def: &ast::Item, edition:
             s.iter().map(|m| {
                 if let MatchedNonterminal(ref nt) = *m {
                     if let NtTT(ref tt) = **nt {
-                        let tt = quoted::parse(tt.clone().into(), true, sess, features, &def.attrs)
-                            .pop().unwrap();
+                        let tt = quoted::parse(
+                            tt.clone().into(),
+                            true,
+                            sess,
+                            features,
+                            &def.attrs,
+                            edition,
+                            def.id,
+                        )
+                        .pop()
+                        .unwrap();
                         valid &= check_lhs_nt_follows(sess, features, &def.attrs, &tt);
                         return tt;
                     }
@@ -257,8 +266,16 @@ pub fn compile(sess: &ParseSess, features: &Features, def: &ast::Item, edition:
             s.iter().map(|m| {
                 if let MatchedNonterminal(ref nt) = *m {
                     if let NtTT(ref tt) = **nt {
-                        return quoted::parse(tt.clone().into(), false, sess, features, &def.attrs)
-                            .pop().unwrap();
+                        return quoted::parse(
+                            tt.clone().into(),
+                            false,
+                            sess,
+                            features,
+                            &def.attrs,
+                            edition,
+                            def.id,
+                        ).pop()
+                         .unwrap();
                     }
                 }
                 sess.span_diagnostic.span_bug(def.span, "wrong-structured lhs")