Rollup merge of #48461 - Manishearth:epoch-dyn-trait, r=nmatsakis

Fixes #47311.
r? @nrc

Author: Manishearth

src/librustc/hir/lowering.rs

@@ -46,7 +46,7 @@ use hir::HirVec;
 use hir::map::{Definitions, DefKey, DefPathData};
 use hir::def_id::{DefIndex, DefId, CRATE_DEF_INDEX, DefIndexAddressSpace};
 use hir::def::{Def, PathResolution};
-use lint::builtin::PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES;
+use lint::builtin::{self, PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES};
 use middle::cstore::CrateStore;
 use rustc_data_structures::indexed_vec::IndexVec;
 use session::Session;
@@ -912,7 +912,11 @@ impl<'a> LoweringContext<'a> {
             TyKind::Path(ref qself, ref path) => {
                 let id = self.lower_node_id(t.id);
                 let qpath = self.lower_qpath(t.id, qself, path, ParamMode::Explicit, itctx);
-                return self.ty_path(id, t.span, qpath);
+                let ty = self.ty_path(id, t.span, qpath);
+                if let hir::TyTraitObject(..) = ty.node {
+                    self.maybe_lint_bare_trait(t.span, t.id, qself.is_none() && path.is_global());
+                }
+                return ty;
             }
             TyKind::ImplicitSelf => {
                 hir::TyPath(hir::QPath::Resolved(None, P(hir::Path {
@@ -931,7 +935,7 @@ impl<'a> LoweringContext<'a> {
                 let expr = self.lower_body(None, |this| this.lower_expr(expr));
                 hir::TyTypeof(expr)
             }
-            TyKind::TraitObject(ref bounds, ..) => {
+            TyKind::TraitObject(ref bounds, kind) => {
                 let mut lifetime_bound = None;
                 let bounds = bounds.iter().filter_map(|bound| {
                     match *bound {
@@ -950,6 +954,9 @@ impl<'a> LoweringContext<'a> {
                 let lifetime_bound = lifetime_bound.unwrap_or_else(|| {
                     self.elided_lifetime(t.span)
                 });
+                if kind != TraitObjectSyntax::Dyn {
+                    self.maybe_lint_bare_trait(t.span, t.id, false);
+                }
                 hir::TyTraitObject(bounds, lifetime_bound)
             }
             TyKind::ImplTrait(ref bounds) => {
@@ -3685,7 +3692,6 @@ impl<'a> LoweringContext<'a> {
                     // The original ID is taken by the `PolyTraitRef`,
                     // so the `Ty` itself needs a different one.
                     id = self.next_id();
-
                     hir::TyTraitObject(hir_vec![principal], self.elided_lifetime(span))
                 } else {
                     hir::TyPath(hir::QPath::Resolved(None, path))
@@ -3703,6 +3709,16 @@ impl<'a> LoweringContext<'a> {
             name: hir::LifetimeName::Implicit,
         }
     }
+
+    fn maybe_lint_bare_trait(&self, span: Span, id: NodeId, is_global: bool) {
+        if self.sess.features.borrow().dyn_trait {
+            self.sess.buffer_lint_with_diagnostic(
+                builtin::BARE_TRAIT_OBJECT, id, span,
+                "trait objects without an explicit `dyn` are deprecated",
+                builtin::BuiltinLintDiagnostics::BareTraitObject(span, is_global)
+            )
+        }
+    }
 }
 
 fn body_ids(bodies: &BTreeMap<hir::BodyId, hir::Body>) -> Vec<hir::BodyId> {

src/librustc/lib.rs

@@ -41,6 +41,8 @@
        html_root_url = "https://doc.rust-lang.org/nightly/")]
 #![deny(warnings)]
 
+#![cfg_attr(not(stage0), allow(bare_trait_object))]
+
 #![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(conservative_impl_trait)]

src/librustc/lint/builtin.rs

@@ -14,7 +14,11 @@
 //! compiler code, rather than using their own custom pass. Those
 //! lints are all available in `rustc_lint::builtin`.
 
+use errors::DiagnosticBuilder;
 use lint::{LintPass, LateLintPass, LintArray};
+use session::Session;
+use session::config::Epoch;
+use syntax::codemap::Span;
 
 declare_lint! {
     pub CONST_ERR,
@@ -252,6 +256,13 @@ declare_lint! {
     "hidden lifetime parameters are deprecated, try `Foo<'_>`"
 }
 
+declare_lint! {
+    pub BARE_TRAIT_OBJECT,
+    Warn,
+    "suggest using `dyn Trait` for trait objects",
+    Epoch::Epoch2018
+}
+
 /// Does nothing as a lint pass, but registers some `Lint`s
 /// which are used by other parts of the compiler.
 #[derive(Copy, Clone)]
@@ -298,10 +309,34 @@ impl LintPass for HardwiredLints {
             COERCE_NEVER,
             SINGLE_USE_LIFETIME,
             TYVAR_BEHIND_RAW_POINTER,
-            ELIDED_LIFETIME_IN_PATH
-
+            ELIDED_LIFETIME_IN_PATH,
+            BARE_TRAIT_OBJECT
         )
     }
 }
 
+// this could be a closure, but then implementing derive traits
+// becomes hacky (and it gets allocated)
+#[derive(PartialEq, RustcEncodable, RustcDecodable, Debug)]
+pub enum BuiltinLintDiagnostics {
+    Normal,
+    BareTraitObject(Span, /* is_global */ bool)
+}
+
+impl BuiltinLintDiagnostics {
+    pub fn run(self, sess: &Session, db: &mut DiagnosticBuilder) {
+        match self {
+            BuiltinLintDiagnostics::Normal => (),
+            BuiltinLintDiagnostics::BareTraitObject(span, is_global) => {
+                let sugg = match sess.codemap().span_to_snippet(span) {
+                    Ok(ref s) if is_global => format!("dyn ({})", s),
+                    Ok(s) => format!("dyn {}", s),
+                    Err(_) => format!("dyn <type>")
+                };
+                db.span_suggestion(span, "use `dyn`", sugg);
+            }
+        }
+    }
+}
+
 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for HardwiredLints {}

src/librustc/lint/context.rs

@@ -29,6 +29,7 @@ use self::TargetLint::*;
 use std::slice;
 use lint::{EarlyLintPassObject, LateLintPassObject};
 use lint::{Level, Lint, LintId, LintPass, LintBuffer};
+use lint::builtin::BuiltinLintDiagnostics;
 use lint::levels::{LintLevelSets, LintLevelsBuilder};
 use middle::privacy::AccessLevels;
 use rustc_serialize::{Decoder, Decodable, Encoder, Encodable};
@@ -92,14 +93,19 @@ pub struct BufferedEarlyLint {
     pub ast_id: ast::NodeId,
     pub span: MultiSpan,
     pub msg: String,
+    pub diagnostic: BuiltinLintDiagnostics,
 }
 
 /// Extra information for a future incompatibility lint. See the call
 /// to `register_future_incompatible` in `librustc_lint/lib.rs` for
 /// guidelines.
 pub struct FutureIncompatibleInfo {
     pub id: LintId,
-    pub reference: &'static str // e.g., a URL for an issue/PR/RFC or error code
+    /// e.g., a URL for an issue/PR/RFC or error code
+    pub reference: &'static str,
+    /// If this is an epoch fixing lint, the epoch in which
+    /// this lint becomes obsolete
+    pub epoch: Option<config::Epoch>,
 }
 
 /// The target of the `by_name` map, which accounts for renaming/deprecation.
@@ -194,11 +200,24 @@ impl LintStore {
     pub fn register_future_incompatible(&mut self,
                                         sess: Option<&Session>,
                                         lints: Vec<FutureIncompatibleInfo>) {
-        let ids = lints.iter().map(|f| f.id).collect();
-        self.register_group(sess, false, "future_incompatible", ids);
-        for info in lints {
-            self.future_incompatible.insert(info.id, info);
+
+        for epoch in config::ALL_EPOCHS {
+            let lints = lints.iter().filter(|f| f.epoch == Some(*epoch)).map(|f| f.id)
+                             .collect::<Vec<_>>();
+            if !lints.is_empty() {
+                self.register_group(sess, false, epoch.lint_name(), lints)
+            }
         }
+
+        let mut future_incompatible = vec![];
+        for lint in lints {
+            future_incompatible.push(lint.id);
+            self.future_incompatible.insert(lint.id, lint);
+        }
+
+        self.register_group(sess, false, "future_incompatible", future_incompatible);
+
+
     }
 
     pub fn future_incompatible(&self, id: LintId) -> Option<&FutureIncompatibleInfo> {
@@ -429,6 +448,16 @@ pub trait LintContext<'tcx>: Sized {
         self.lookup(lint, span, msg).emit();
     }
 
+    fn lookup_and_emit_with_diagnostics<S: Into<MultiSpan>>(&self,
+                                                            lint: &'static Lint,
+                                                            span: Option<S>,
+                                                            msg: &str,
+                                                            diagnostic: BuiltinLintDiagnostics) {
+        let mut db = self.lookup(lint, span, msg);
+        diagnostic.run(self.sess(), &mut db);
+        db.emit();
+    }
+
     fn lookup<S: Into<MultiSpan>>(&self,
                                   lint: &'static Lint,
                                   span: Option<S>,
@@ -499,9 +528,10 @@ impl<'a> EarlyContext<'a> {
 
     fn check_id(&mut self, id: ast::NodeId) {
         for early_lint in self.buffered.take(id) {
-            self.lookup_and_emit(early_lint.lint_id.lint,
-                                 Some(early_lint.span.clone()),
-                                 &early_lint.msg);
+            self.lookup_and_emit_with_diagnostics(early_lint.lint_id.lint,
+                                                  Some(early_lint.span.clone()),
+                                                  &early_lint.msg,
+                                                  early_lint.diagnostic);
         }
     }
 }
@@ -1054,7 +1084,7 @@ pub fn check_ast_crate(sess: &Session, krate: &ast::Crate) {
     if !sess.opts.actually_rustdoc {
         for (_id, lints) in cx.buffered.map {
             for early_lint in lints {
-                span_bug!(early_lint.span, "failed to process buffered lint here");
+                sess.delay_span_bug(early_lint.span, "failed to process buffered lint here");
             }
         }
     }

src/librustc/lint/levels.rs

@@ -89,14 +89,15 @@ impl LintLevelSets {
     fn get_lint_level(&self,
                       lint: &'static Lint,
                       idx: u32,
-                      aux: Option<&FxHashMap<LintId, (Level, LintSource)>>)
+                      aux: Option<&FxHashMap<LintId, (Level, LintSource)>>,
+                      sess: &Session)
         -> (Level, LintSource)
     {
         let (level, mut src) = self.get_lint_id_level(LintId::of(lint), idx, aux);
 
         // If `level` is none then we actually assume the default level for this
         // lint.
-        let mut level = level.unwrap_or(lint.default_level);
+        let mut level = level.unwrap_or(lint.default_level(sess));
 
         // If we're about to issue a warning, check at the last minute for any
         // directives against the warnings "lint". If, for example, there's an
@@ -235,7 +236,8 @@ impl<'a> LintLevelsBuilder<'a> {
                         let lint = builtin::RENAMED_AND_REMOVED_LINTS;
                         let (level, src) = self.sets.get_lint_level(lint,
                                                                     self.cur,
-                                                                    Some(&specs));
+                                                                    Some(&specs),
+                                                                    &sess);
                         lint::struct_lint_level(self.sess,
                                                 lint,
                                                 level,
@@ -248,7 +250,8 @@ impl<'a> LintLevelsBuilder<'a> {
                         let lint = builtin::UNKNOWN_LINTS;
                         let (level, src) = self.sets.get_lint_level(lint,
                                                                     self.cur,
-                                                                    Some(&specs));
+                                                                    Some(&specs),
+                                                                    self.sess);
                         let msg = format!("unknown lint: `{}`", name);
                         let mut db = lint::struct_lint_level(self.sess,
                                                 lint,
@@ -342,7 +345,7 @@ impl<'a> LintLevelsBuilder<'a> {
                        msg: &str)
         -> DiagnosticBuilder<'a>
     {
-        let (level, src) = self.sets.get_lint_level(lint, self.cur, None);
+        let (level, src) = self.sets.get_lint_level(lint, self.cur, None, self.sess);
         lint::struct_lint_level(self.sess, lint, level, src, span, msg)
     }
 
@@ -377,11 +380,11 @@ impl LintLevelMap {
     /// If the `id` was not previously registered, returns `None`. If `None` is
     /// returned then the parent of `id` should be acquired and this function
     /// should be called again.
-    pub fn level_and_source(&self, lint: &'static Lint, id: HirId)
+    pub fn level_and_source(&self, lint: &'static Lint, id: HirId, session: &Session)
         -> Option<(Level, LintSource)>
     {
         self.id_to_set.get(&id).map(|idx| {
-            self.sets.get_lint_level(lint, *idx, None)
+            self.sets.get_lint_level(lint, *idx, None, session)
         })
     }
 

src/librustc/lint/mod.rs

@@ -37,7 +37,8 @@ use errors::{DiagnosticBuilder, DiagnosticId};
 use hir::def_id::{CrateNum, LOCAL_CRATE};
 use hir::intravisit::{self, FnKind};
 use hir;
-use session::{Session, DiagnosticMessageId};
+use lint::builtin::BuiltinLintDiagnostics;
+use session::{config, Session, DiagnosticMessageId};
 use std::hash;
 use syntax::ast;
 use syntax::codemap::MultiSpan;
@@ -74,25 +75,46 @@ pub struct Lint {
     ///
     /// e.g. "imports that are never used"
     pub desc: &'static str,
+
+    /// Deny lint after this epoch
+    pub epoch_deny: Option<config::Epoch>,
 }
 
 impl Lint {
     /// Get the lint's name, with ASCII letters converted to lowercase.
     pub fn name_lower(&self) -> String {
         self.name.to_ascii_lowercase()
     }
+
+    pub fn default_level(&self, session: &Session) -> Level {
+        if let Some(epoch_deny) = self.epoch_deny {
+            if session.epoch() >= epoch_deny {
+                return Level::Deny
+            }
+        }
+        self.default_level
+    }
 }
 
 /// Declare a static item of type `&'static Lint`.
 #[macro_export]
 macro_rules! declare_lint {
+    ($vis: vis $NAME: ident, $Level: ident, $desc: expr, $epoch: expr) => (
+        $vis static $NAME: &$crate::lint::Lint = &$crate::lint::Lint {
+            name: stringify!($NAME),
+            default_level: $crate::lint::$Level,
+            desc: $desc,
+            epoch_deny: Some($epoch)
+        };
+    );
     ($vis: vis $NAME: ident, $Level: ident, $desc: expr) => (
         $vis static $NAME: &$crate::lint::Lint = &$crate::lint::Lint {
             name: stringify!($NAME),
             default_level: $crate::lint::$Level,
-            desc: $desc
+            desc: $desc,
+            epoch_deny: None,
         };
-    )
+    );
 }
 
 /// Declare a static `LintArray` and return it as an expression.
@@ -304,7 +326,7 @@ impl LintId {
 /// Setting for how to handle a lint.
 #[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Debug, Hash)]
 pub enum Level {
-    Allow, Warn, Deny, Forbid
+    Allow, Warn, Deny, Forbid,
 }
 
 impl_stable_hash_for!(enum self::Level {
@@ -378,12 +400,14 @@ impl LintBuffer {
                     lint: &'static Lint,
                     id: ast::NodeId,
                     sp: MultiSpan,
-                    msg: &str) {
+                    msg: &str,
+                    diagnostic: BuiltinLintDiagnostics) {
         let early_lint = BufferedEarlyLint {
             lint_id: LintId::of(lint),
             ast_id: id,
             span: sp,
             msg: msg.to_string(),
+            diagnostic
         };
         let arr = self.map.entry(id).or_insert(Vec::new());
         if !arr.contains(&early_lint) {