Internal lints take 2

src/bootstrap/bin/rustc.rs

@@ -316,6 +316,11 @@ fn main() {
         }
     }
 
+    // This is required for internal lints.
+    if stage != "0" {
+        cmd.arg("-Zunstable-options");
+    }
+
     // Force all crates compiled by this compiler to (a) be unstable and (b)
     // allow the `rustc_private` feature to link to other unstable crates
     // also in the sysroot. We also do this for host crates, since those

src/libarena/lib.rs

@@ -12,6 +12,7 @@
        test(no_crate_inject, attr(deny(warnings))))]
 
 #![deny(rust_2018_idioms)]
+#![cfg_attr(not(stage0), deny(internal))]
 
 #![feature(alloc)]
 #![feature(core_intrinsics)]

src/libfmt_macros/lib.rs

@@ -9,6 +9,7 @@
        test(attr(deny(warnings))))]
 
 #![deny(rust_2018_idioms)]
+#![cfg_attr(not(stage0), deny(internal))]
 
 #![feature(nll)]
 #![feature(rustc_private)]

src/librustc/hir/def_id.rs

@@ -1,10 +1,10 @@
-use crate::ty;
-use crate::ty::TyCtxt;
-use crate::hir::map::definitions::FIRST_FREE_HIGH_DEF_INDEX;
+use crate::ty::{self, print::Printer, subst::Kind, Ty, TyCtxt};
+use crate::hir::map::definitions::{DisambiguatedDefPathData, FIRST_FREE_HIGH_DEF_INDEX};
 use rustc_data_structures::indexed_vec::Idx;
 use serialize;
 use std::fmt;
 use std::u32;
+use syntax::symbol::{LocalInternedString, Symbol};
 
 newtype_index! {
     pub struct CrateId {
@@ -252,6 +252,107 @@ impl DefId {
             format!("module `{}`", tcx.def_path_str(*self))
         }
     }
+
+    /// Check if a `DefId`'s path matches the given absolute type path usage.
+    // Uplifted from rust-lang/rust-clippy
+    pub fn match_path<'a, 'tcx>(self, tcx: TyCtxt<'a, 'tcx, 'tcx>, path: &[&str]) -> bool {
+        pub struct AbsolutePathPrinter<'a, 'tcx> {
+            pub tcx: TyCtxt<'a, 'tcx, 'tcx>,
+        }
+
+        impl<'tcx> Printer<'tcx, 'tcx> for AbsolutePathPrinter<'_, 'tcx> {
+            type Error = !;
+
+            type Path = Vec<LocalInternedString>;
+            type Region = ();
+            type Type = ();
+            type DynExistential = ();
+
+            fn tcx<'a>(&'a self) -> TyCtxt<'a, 'tcx, 'tcx> {
+                self.tcx
+            }
+
+            fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
+                Ok(())
+            }
+
+            fn print_type(self, _ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
+                Ok(())
+            }
+
+            fn print_dyn_existential(
+                self,
+                _predicates: &'tcx ty::List<ty::ExistentialPredicate<'tcx>>,
+                ) -> Result<Self::DynExistential, Self::Error> {
+                Ok(())
+            }
+
+            fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
+                Ok(vec![self.tcx.original_crate_name(cnum).as_str()])
+            }
+
+            fn path_qualified(
+                self,
+                self_ty: Ty<'tcx>,
+                trait_ref: Option<ty::TraitRef<'tcx>>,
+                ) -> Result<Self::Path, Self::Error> {
+                if trait_ref.is_none() {
+                    if let ty::Adt(def, substs) = self_ty.sty {
+                        return self.print_def_path(def.did, substs);
+                    }
+                }
+
+                // This shouldn't ever be needed, but just in case:
+                Ok(vec![match trait_ref {
+                    Some(trait_ref) => Symbol::intern(&format!("{:?}", trait_ref)).as_str(),
+                    None => Symbol::intern(&format!("<{}>", self_ty)).as_str(),
+                }])
+            }
+
+            fn path_append_impl(
+                self,
+                print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
+                _disambiguated_data: &DisambiguatedDefPathData,
+                self_ty: Ty<'tcx>,
+                trait_ref: Option<ty::TraitRef<'tcx>>,
+                ) -> Result<Self::Path, Self::Error> {
+                let mut path = print_prefix(self)?;
+
+                // This shouldn't ever be needed, but just in case:
+                path.push(match trait_ref {
+                    Some(trait_ref) => {
+                        Symbol::intern(&format!("<impl {} for {}>", trait_ref, self_ty)).as_str()
+                    },
+                    None => Symbol::intern(&format!("<impl {}>", self_ty)).as_str(),
+                });
+
+                Ok(path)
+            }
+
+            fn path_append(
+                self,
+                print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
+                disambiguated_data: &DisambiguatedDefPathData,
+                ) -> Result<Self::Path, Self::Error> {
+                let mut path = print_prefix(self)?;
+                path.push(disambiguated_data.data.as_interned_str().as_str());
+                Ok(path)
+            }
+
+            fn path_generic_args(
+                self,
+                print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
+                _args: &[Kind<'tcx>],
+                ) -> Result<Self::Path, Self::Error> {
+                print_prefix(self)
+            }
+        }
+
+        let names = AbsolutePathPrinter { tcx }.print_def_path(self, &[]).unwrap();
+
+        names.len() == path.len()
+            && names.into_iter().zip(path.iter()).all(|(a, &b)| *a == *b)
+    }
 }
 
 impl serialize::UseSpecializedEncodable for DefId {}

src/librustc/ich/hcx.rs

@@ -9,7 +9,6 @@ use crate::session::Session;
 
 use std::cmp::Ord;
 use std::hash as std_hash;
-use std::collections::HashMap;
 use std::cell::RefCell;
 
 use syntax::ast;
@@ -394,13 +393,12 @@ impl<'a> HashStable<StableHashingContext<'a>> for DelimSpan {
     }
 }
 
-pub fn hash_stable_trait_impls<'a, 'gcx, W, R>(
+pub fn hash_stable_trait_impls<'a, 'gcx, W>(
     hcx: &mut StableHashingContext<'a>,
     hasher: &mut StableHasher<W>,
     blanket_impls: &[DefId],
-    non_blanket_impls: &HashMap<fast_reject::SimplifiedType, Vec<DefId>, R>)
-    where W: StableHasherResult,
-          R: std_hash::BuildHasher,
+    non_blanket_impls: &FxHashMap<fast_reject::SimplifiedType, Vec<DefId>>)
+    where W: StableHasherResult
 {
     {
         let mut blanket_impls: SmallVec<[_; 8]> = blanket_impls

src/librustc/infer/error_reporting/mod.rs

@@ -56,7 +56,7 @@ use crate::hir::Node;
 use crate::middle::region;
 use crate::traits::{ObligationCause, ObligationCauseCode};
 use crate::ty::error::TypeError;
-use crate::ty::{self, subst::{Subst, SubstsRef}, Region, Ty, TyCtxt, TyKind, TypeFoldable};
+use crate::ty::{self, subst::{Subst, SubstsRef}, Region, Ty, TyCtxt, TypeFoldable};
 use errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString};
 use std::{cmp, fmt};
 use syntax_pos::{Pos, Span};
@@ -1094,14 +1094,14 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                 (_, false, _) => {
                     if let Some(exp_found) = exp_found {
                         let (def_id, ret_ty) = match exp_found.found.sty {
-                            TyKind::FnDef(def, _) => {
+                            ty::FnDef(def, _) => {
                                 (Some(def), Some(self.tcx.fn_sig(def).output()))
                             }
                             _ => (None, None),
                         };
 
                         let exp_is_struct = match exp_found.expected.sty {
-                            TyKind::Adt(def, _) => def.is_struct(),
+                            ty::Adt(def, _) => def.is_struct(),
                             _ => false,
                         };
 
@@ -1140,8 +1140,8 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         diag: &mut DiagnosticBuilder<'tcx>,
     ) {
         match (&exp_found.expected.sty, &exp_found.found.sty) {
-            (TyKind::Adt(exp_def, exp_substs), TyKind::Ref(_, found_ty, _)) => {
-                if let TyKind::Adt(found_def, found_substs) = found_ty.sty {
+            (ty::Adt(exp_def, exp_substs), ty::Ref(_, found_ty, _)) => {
+                if let ty::Adt(found_def, found_substs) = found_ty.sty {
                     let path_str = format!("{:?}", exp_def);
                     if exp_def == &found_def {
                         let opt_msg = "you can convert from `&Option<T>` to `Option<&T>` using \
@@ -1164,17 +1164,17 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                             let mut show_suggestion = true;
                             for (exp_ty, found_ty) in exp_substs.types().zip(found_substs.types()) {
                                 match exp_ty.sty {
-                                    TyKind::Ref(_, exp_ty, _) => {
+                                    ty::Ref(_, exp_ty, _) => {
                                         match (&exp_ty.sty, &found_ty.sty) {
-                                            (_, TyKind::Param(_)) |
-                                            (_, TyKind::Infer(_)) |
-                                            (TyKind::Param(_), _) |
-                                            (TyKind::Infer(_), _) => {}
+                                            (_, ty::Param(_)) |
+                                            (_, ty::Infer(_)) |
+                                            (ty::Param(_), _) |
+                                            (ty::Infer(_), _) => {}
                                             _ if ty::TyS::same_type(exp_ty, found_ty) => {}
                                             _ => show_suggestion = false,
                                         };
                                     }
-                                    TyKind::Param(_) | TyKind::Infer(_) => {}
+                                    ty::Param(_) | ty::Infer(_) => {}
                                     _ => show_suggestion = false,
                                 }
                             }

src/librustc/lib.rs

@@ -29,6 +29,7 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
 
 #![deny(rust_2018_idioms)]
+#![cfg_attr(not(stage0), deny(internal))]
 #![allow(explicit_outlives_requirements)]
 
 #![feature(arbitrary_self_types)]

src/librustc/lint/internal.rs

@@ -0,0 +1,127 @@
+//! Some lints that are only useful in the compiler or crates that use compiler internals, such as
+//! Clippy.
+
+use crate::hir::{HirId, Path, PathSegment, QPath, Ty, TyKind};
+use crate::lint::{
+    EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintArray, LintContext, LintPass,
+};
+use errors::Applicability;
+use rustc_data_structures::fx::FxHashMap;
+use syntax::ast::Ident;
+
+declare_lint! {
+    pub DEFAULT_HASH_TYPES,
+    Allow,
+    "forbid HashMap and HashSet and suggest the FxHash* variants"
+}
+
+pub struct DefaultHashTypes {
+    map: FxHashMap<String, String>,
+}
+
+impl DefaultHashTypes {
+    pub fn new() -> Self {
+        let mut map = FxHashMap::default();
+        map.insert("HashMap".to_string(), "FxHashMap".to_string());
+        map.insert("HashSet".to_string(), "FxHashSet".to_string());
+        Self { map }
+    }
+}
+
+impl LintPass for DefaultHashTypes {
+    fn get_lints(&self) -> LintArray {
+        lint_array!(DEFAULT_HASH_TYPES)
+    }
+
+    fn name(&self) -> &'static str {
+        "DefaultHashTypes"
+    }
+}
+
+impl EarlyLintPass for DefaultHashTypes {
+    fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
+        let ident_string = ident.to_string();
+        if let Some(replace) = self.map.get(&ident_string) {
+            let msg = format!(
+                "Prefer {} over {}, it has better performance",
+                replace, ident_string
+            );
+            let mut db = cx.struct_span_lint(DEFAULT_HASH_TYPES, ident.span, &msg);
+            db.span_suggestion(
+                ident.span,
+                "use",
+                replace.to_string(),
+                Applicability::MaybeIncorrect, // FxHashMap, ... needs another import
+            );
+            db.note(&format!(
+                "a `use rustc_data_structures::fx::{}` may be necessary",
+                replace
+            ))
+            .emit();
+        }
+    }
+}
+
+declare_lint! {
+    pub USAGE_OF_TY_TYKIND,
+    Allow,
+    "Usage of `ty::TyKind` outside of the `ty::sty` module"
+}
+
+pub struct TyKindUsage;
+
+impl LintPass for TyKindUsage {
+    fn get_lints(&self) -> LintArray {
+        lint_array!(USAGE_OF_TY_TYKIND)
+    }
+
+    fn name(&self) -> &'static str {
+        "TyKindUsage"
+    }
+}
+
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TyKindUsage {
+    fn check_path(&mut self, cx: &LateContext<'_, '_>, path: &'tcx Path, _: HirId) {
+        let segments = path.segments.iter().rev().skip(1).rev();
+
+        if let Some(last) = segments.last() {
+            let span = path.span.with_hi(last.ident.span.hi());
+            if lint_ty_kind_usage(cx, last) {
+                cx.struct_span_lint(USAGE_OF_TY_TYKIND, span, "usage of `ty::TyKind::<kind>`")
+                    .span_suggestion(
+                        span,
+                        "try using ty::<kind> directly",
+                        "ty".to_string(),
+                        Applicability::MaybeIncorrect, // ty maybe needs an import
+                    )
+                    .emit();
+            }
+        }
+    }
+
+    fn check_ty(&mut self, cx: &LateContext<'_, '_>, ty: &'tcx Ty) {
+        if let TyKind::Path(qpath) = &ty.node {
+            if let QPath::Resolved(_, path) = qpath {
+                if let Some(last) = path.segments.iter().last() {
+                    if lint_ty_kind_usage(cx, last) {
+                        cx.struct_span_lint(USAGE_OF_TY_TYKIND, path.span, "usage of `ty::TyKind`")
+                            .help("try using `ty::Ty` instead")
+                            .emit();
+                    }
+                }
+            }
+        }
+    }
+}
+
+fn lint_ty_kind_usage(cx: &LateContext<'_, '_>, segment: &PathSegment) -> bool {
+    if segment.ident.as_str() == "TyKind" {
+        if let Some(def) = segment.def {
+            if let Some(did) = def.opt_def_id() {
+                return did.match_path(cx.tcx, &["rustc", "ty", "sty", "TyKind"]);
+            }
+        }
+    }
+
+    false
+}

src/librustc/lint/mod.rs

@@ -574,6 +574,7 @@ impl_stable_hash_for!(enum self::LintSource {
 pub type LevelSource = (Level, LintSource);
 
 pub mod builtin;
+pub mod internal;
 mod context;
 mod levels;
 

src/librustc/mir/tcx.rs

@@ -36,7 +36,7 @@ impl<'a, 'gcx, 'tcx> PlaceTy<'tcx> {
     pub fn field_ty(self, tcx: TyCtxt<'a, 'gcx, 'tcx>, f: &Field) -> Ty<'tcx>
     {
         let answer = match self.ty.sty {
-            ty::TyKind::Adt(adt_def, substs) => {
+            ty::Adt(adt_def, substs) => {
                 let variant_def = match self.variant_index {
                     None => adt_def.non_enum_variant(),
                     Some(variant_index) => {