Rollup merge of rust-lang#74070 - eddyb:forall-tcx-providers, r=nikomatsakis

 Use for<'tcx> fn pointers in Providers, instead of having Providers<'tcx>.

In order to work around normalization-under-HRTB (for `provide!` in `rustc_metadata`), we ended up with this:
```rust
struct Providers<'tcx> {
    type_of: fn(TyCtxt<'tcx>, DefId) -> Ty<'tcx>,
    // ...
}
```
But what I initially wanted to do, IIRC, was this:
```rust
struct Providers {
    type_of: for<'tcx> fn(TyCtxt<'tcx>, DefId) -> Ty<'tcx>,
    // ...
}
```

This PR moves to the latter, for the simple reason that only the latter allows keeping a `Providers` value, or a subset of its `fn` pointer fields, around in a `static` or `thread_local!`, which can be really useful for custom drivers that override queries.
(@jyn514 and I came across a concrete usecase of that in `rustdoc`)

The `provide!` macro in `rustc_metadata` is fixed by making the query key/value types available as type aliases under `ty::query::query_{keys,values}`, not just associated types (this is the first commit).

r? @nikomatsakis

Author: Manishearth

src/librustc_codegen_llvm/attributes.rs

@@ -342,7 +342,7 @@ pub fn from_fn_attrs(cx: &CodegenCx<'ll, 'tcx>, llfn: &'ll Value, instance: ty::
     }
 }
 
-pub fn provide(providers: &mut Providers<'_>) {
+pub fn provide(providers: &mut Providers) {
     providers.target_features_whitelist = |tcx, cnum| {
         assert_eq!(cnum, LOCAL_CRATE);
         if tcx.sess.opts.actually_rustdoc {
@@ -360,7 +360,7 @@ pub fn provide(providers: &mut Providers<'_>) {
     provide_extern(providers);
 }
 
-pub fn provide_extern(providers: &mut Providers<'_>) {
+pub fn provide_extern(providers: &mut Providers) {
     providers.wasm_import_module_map = |tcx, cnum| {
         // Build up a map from DefId to a `NativeLib` structure, where
         // `NativeLib` internally contains information about

src/librustc_codegen_llvm/lib.rs

@@ -241,11 +241,11 @@ impl CodegenBackend for LlvmCodegenBackend {
         Box::new(metadata::LlvmMetadataLoader)
     }
 
-    fn provide(&self, providers: &mut ty::query::Providers<'_>) {
+    fn provide(&self, providers: &mut ty::query::Providers) {
         attributes::provide(providers);
     }
 
-    fn provide_extern(&self, providers: &mut ty::query::Providers<'_>) {
+    fn provide_extern(&self, providers: &mut ty::query::Providers) {
         attributes::provide_extern(providers);
     }
 

src/librustc_codegen_ssa/back/symbol_export.rs

@@ -161,9 +161,9 @@ fn is_reachable_non_generic_provider_extern(tcx: TyCtxt<'_>, def_id: DefId) -> b
 }
 
 fn exported_symbols_provider_local(
-    tcx: TyCtxt<'_>,
+    tcx: TyCtxt<'tcx>,
     cnum: CrateNum,
-) -> &'tcx [(ExportedSymbol<'_>, SymbolExportLevel)] {
+) -> &'tcx [(ExportedSymbol<'tcx>, SymbolExportLevel)] {
     assert_eq!(cnum, LOCAL_CRATE);
 
     if !tcx.sess.opts.output_types.should_codegen() {
@@ -366,7 +366,7 @@ fn is_unreachable_local_definition_provider(tcx: TyCtxt<'_>, def_id: DefId) -> b
     }
 }
 
-pub fn provide(providers: &mut Providers<'_>) {
+pub fn provide(providers: &mut Providers) {
     providers.reachable_non_generics = reachable_non_generics_provider;
     providers.is_reachable_non_generic = is_reachable_non_generic_provider_local;
     providers.exported_symbols = exported_symbols_provider_local;
@@ -375,7 +375,7 @@ pub fn provide(providers: &mut Providers<'_>) {
     providers.upstream_drop_glue_for = upstream_drop_glue_for_provider;
 }
 
-pub fn provide_extern(providers: &mut Providers<'_>) {
+pub fn provide_extern(providers: &mut Providers) {
     providers.is_reachable_non_generic = is_reachable_non_generic_provider_extern;
     providers.upstream_monomorphizations_for = upstream_monomorphizations_for_provider;
 }

src/librustc_codegen_ssa/base.rs

@@ -853,7 +853,7 @@ impl CrateInfo {
     }
 }
 
-pub fn provide_both(providers: &mut Providers<'_>) {
+pub fn provide_both(providers: &mut Providers) {
     providers.backend_optimization_level = |tcx, cratenum| {
         let for_speed = match tcx.sess.opts.optimize {
             // If globally no optimisation is done, #[optimize] has no effect.

src/librustc_codegen_ssa/lib.rs

@@ -138,12 +138,12 @@ pub struct CodegenResults {
     pub crate_info: CrateInfo,
 }
 
-pub fn provide(providers: &mut Providers<'_>) {
+pub fn provide(providers: &mut Providers) {
     crate::back::symbol_export::provide(providers);
     crate::base::provide_both(providers);
 }
 
-pub fn provide_extern(providers: &mut Providers<'_>) {
+pub fn provide_extern(providers: &mut Providers) {
     crate::back::symbol_export::provide_extern(providers);
     crate::base::provide_both(providers);
 }

src/librustc_codegen_ssa/traits/backend.rs

@@ -55,8 +55,8 @@ pub trait CodegenBackend {
     fn print_version(&self) {}
 
     fn metadata_loader(&self) -> Box<MetadataLoaderDyn>;
-    fn provide(&self, _providers: &mut Providers<'_>);
-    fn provide_extern(&self, _providers: &mut Providers<'_>);
+    fn provide(&self, _providers: &mut Providers);
+    fn provide_extern(&self, _providers: &mut Providers);
     fn codegen_crate<'tcx>(
         &self,
         tcx: TyCtxt<'tcx>,

src/librustc_interface/interface.rs

@@ -38,7 +38,7 @@ pub struct Compiler {
     pub(crate) crate_name: Option<String>,
     pub(crate) register_lints: Option<Box<dyn Fn(&Session, &mut LintStore) + Send + Sync>>,
     pub(crate) override_queries:
-        Option<fn(&Session, &mut ty::query::Providers<'_>, &mut ty::query::Providers<'_>)>,
+        Option<fn(&Session, &mut ty::query::Providers, &mut ty::query::Providers)>,
 }
 
 impl Compiler {
@@ -153,7 +153,7 @@ pub struct Config {
     ///
     /// The second parameter is local providers and the third parameter is external providers.
     pub override_queries:
-        Option<fn(&Session, &mut ty::query::Providers<'_>, &mut ty::query::Providers<'_>)>,
+        Option<fn(&Session, &mut ty::query::Providers, &mut ty::query::Providers)>,
 
     /// Registry of diagnostics codes.
     pub registry: Registry,

src/librustc_interface/passes.rs

@@ -719,7 +719,7 @@ pub fn prepare_outputs(
     Ok(outputs)
 }
 
-pub fn default_provide(providers: &mut ty::query::Providers<'_>) {
+pub fn default_provide(providers: &mut ty::query::Providers) {
     providers.analysis = analysis;
     proc_macro_decls::provide(providers);
     plugin::build::provide(providers);
@@ -740,7 +740,7 @@ pub fn default_provide(providers: &mut ty::query::Providers<'_>) {
     rustc_codegen_ssa::provide(providers);
 }
 
-pub fn default_provide_extern(providers: &mut ty::query::Providers<'_>) {
+pub fn default_provide_extern(providers: &mut ty::query::Providers) {
     rustc_metadata::provide_extern(providers);
     rustc_codegen_ssa::provide_extern(providers);
 }

src/librustc_interface/proc_macro_decls.rs

@@ -35,6 +35,6 @@ impl<'v> ItemLikeVisitor<'v> for Finder {
     fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem<'_>) {}
 }
 
-pub(crate) fn provide(providers: &mut Providers<'_>) {
+pub(crate) fn provide(providers: &mut Providers) {
     *providers = Providers { proc_macro_decls_static, ..*providers };
 }

src/librustc_lint/levels.rs

@@ -571,6 +571,6 @@ impl<'tcx> intravisit::Visitor<'tcx> for LintLevelMapBuilder<'_, 'tcx> {
     }
 }
 
-pub fn provide(providers: &mut Providers<'_>) {
+pub fn provide(providers: &mut Providers) {
     providers.lint_levels = lint_levels;
 }

src/librustc_lint/lib.rs

@@ -88,7 +88,7 @@ pub use rustc_session::lint::Level::{self, *};
 pub use rustc_session::lint::{BufferedEarlyLint, FutureIncompatibleInfo, Lint, LintId};
 pub use rustc_session::lint::{LintArray, LintPass};
 
-pub fn provide(providers: &mut Providers<'_>) {
+pub fn provide(providers: &mut Providers) {
     levels::provide(providers);
     *providers = Providers { lint_mod, ..*providers };
 }

src/librustc_metadata/rmeta/decoder/cstore_impl.rs

@@ -17,7 +17,6 @@ use rustc_middle::middle::cstore::{CrateSource, CrateStore, EncodedMetadata};
 use rustc_middle::middle::exported_symbols::ExportedSymbol;
 use rustc_middle::middle::stability::DeprecationEntry;
 use rustc_middle::ty::query::Providers;
-use rustc_middle::ty::query::QueryConfig;
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_session::utils::NativeLibKind;
 use rustc_session::{CrateDisambiguator, Session};
@@ -31,13 +30,11 @@ use std::any::Any;
 macro_rules! provide {
     (<$lt:tt> $tcx:ident, $def_id:ident, $other:ident, $cdata:ident,
       $($name:ident => $compute:block)*) => {
-        pub fn provide_extern<$lt>(providers: &mut Providers<$lt>) {
-            // HACK(eddyb) `$lt: $lt` forces `$lt` to be early-bound, which
-            // allows the associated type in the return type to be normalized.
-            $(fn $name<$lt: $lt, T: IntoArgs>(
+        pub fn provide_extern(providers: &mut Providers) {
+            $(fn $name<$lt>(
                 $tcx: TyCtxt<$lt>,
-                def_id_arg: T,
-            ) -> <ty::queries::$name<$lt> as QueryConfig<TyCtxt<$lt>>>::Value {
+                def_id_arg: ty::query::query_keys::$name<$lt>,
+            ) -> ty::query::query_values::$name<$lt> {
                 let _prof_timer =
                     $tcx.prof.generic_activity("metadata_decode_entry");
 
@@ -243,7 +240,7 @@ provide! { <'tcx> tcx, def_id, other, cdata,
     crate_extern_paths => { cdata.source().paths().cloned().collect() }
 }
 
-pub fn provide(providers: &mut Providers<'_>) {
+pub fn provide(providers: &mut Providers) {
     // FIXME(#44234) - almost all of these queries have no sub-queries and
     // therefore no actual inputs, they're just reading tables calculated in
     // resolve! Does this work? Unsure! That's what the issue is about

src/librustc_middle/hir/map/mod.rs

@@ -1067,6 +1067,6 @@ fn hir_id_to_string(map: &Map<'_>, id: HirId) -> String {
     }
 }
 
-pub fn provide(providers: &mut Providers<'_>) {
+pub fn provide(providers: &mut Providers) {
     providers.def_kind = |tcx, def_id| tcx.hir().def_kind(def_id.expect_local());
 }

src/librustc_middle/hir/mod.rs

@@ -62,7 +62,7 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 }
 
-pub fn provide(providers: &mut Providers<'_>) {
+pub fn provide(providers: &mut Providers) {
     providers.parent_module_from_def_id = |tcx, id| {
         let hir = tcx.hir();
         hir.local_def_id(hir.get_module_parent_node(hir.as_local_hir_id(id)))

src/librustc_middle/ty/context.rs

@@ -1060,8 +1060,8 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn create_global_ctxt(
         s: &'tcx Session,
         lint_store: Lrc<dyn Any + sync::Send + sync::Sync>,
-        local_providers: ty::query::Providers<'tcx>,
-        extern_providers: ty::query::Providers<'tcx>,
+        local_providers: ty::query::Providers,
+        extern_providers: ty::query::Providers,
         arena: &'tcx WorkerLocal<Arena<'tcx>>,
         resolutions: ty::ResolverOutputs,
         krate: &'tcx hir::Crate<'tcx>,
@@ -2699,7 +2699,7 @@ fn ptr_eq<T, U>(t: *const T, u: *const U) -> bool {
     t as *const () == u as *const ()
 }
 
-pub fn provide(providers: &mut ty::query::Providers<'_>) {
+pub fn provide(providers: &mut ty::query::Providers) {
     providers.in_scope_traits_map = |tcx, id| tcx.gcx.trait_map.get(&id);
     providers.module_exports = |tcx, id| tcx.gcx.export_map.get(&id).map(|v| &v[..]);
     providers.crate_name = |tcx, id| {

src/librustc_middle/ty/erase_regions.rs

@@ -1,7 +1,7 @@
 use crate::ty::fold::{TypeFoldable, TypeFolder};
 use crate::ty::{self, Ty, TyCtxt, TypeFlags};
 
-pub(super) fn provide(providers: &mut ty::query::Providers<'_>) {
+pub(super) fn provide(providers: &mut ty::query::Providers) {
     *providers = ty::query::Providers { erase_regions_ty, ..*providers };
 }
 

src/librustc_middle/ty/layout.rs

@@ -210,7 +210,7 @@ fn layout_raw<'tcx>(
     })
 }
 
-pub fn provide(providers: &mut ty::query::Providers<'_>) {
+pub fn provide(providers: &mut ty::query::Providers) {
     *providers = ty::query::Providers { layout_raw, ..*providers };
 }
 

src/librustc_middle/ty/mod.rs

@@ -2966,7 +2966,7 @@ pub fn is_impl_trait_defn(tcx: TyCtxt<'_>, def_id: DefId) -> Option<DefId> {
     None
 }
 
-pub fn provide(providers: &mut ty::query::Providers<'_>) {
+pub fn provide(providers: &mut ty::query::Providers) {
     context::provide(providers);
     erase_regions::provide(providers);
     layout::provide(providers);

src/librustc_middle/ty/query/plumbing.rs

@@ -318,15 +318,34 @@ macro_rules! define_queries_inner {
             }
         }
 
+        #[allow(nonstandard_style)]
         pub mod queries {
             use std::marker::PhantomData;
 
-            $(#[allow(nonstandard_style)]
-            pub struct $name<$tcx> {
+            $(pub struct $name<$tcx> {
                 data: PhantomData<&$tcx ()>
             })*
         }
 
+        // HACK(eddyb) this is like the `impl QueryConfig for queries::$name`
+        // below, but using type aliases instead of associated types, to bypass
+        // the limitations around normalizing under HRTB - for example, this:
+        // `for<'tcx> fn(...) -> <queries::$name<'tcx> as QueryConfig<TyCtxt<'tcx>>>::Value`
+        // doesn't currently normalize to `for<'tcx> fn(...) -> query_values::$name<'tcx>`.
+        // This is primarily used by the `provide!` macro in `rustc_metadata`.
+        #[allow(nonstandard_style, unused_lifetimes)]
+        pub mod query_keys {
+            use super::*;
+
+            $(pub type $name<$tcx> = $($K)*;)*
+        }
+        #[allow(nonstandard_style, unused_lifetimes)]
+        pub mod query_values {
+            use super::*;
+
+            $(pub type $name<$tcx> = $V;)*
+        }
+
         $(impl<$tcx> QueryConfig<TyCtxt<$tcx>> for queries::$name<$tcx> {
             type Key = $($K)*;
             type Value = $V;
@@ -478,13 +497,16 @@ macro_rules! define_queries_inner {
             input: ($(([$($modifiers)*] [$name] [$($K)*] [$V]))*)
         }
 
-        impl<$tcx> Copy for Providers<$tcx> {}
-        impl<$tcx> Clone for Providers<$tcx> {
+        impl Copy for Providers {}
+        impl Clone for Providers {
             fn clone(&self) -> Self { *self }
         }
     }
 }
 
+// FIXME(eddyb) this macro (and others?) use `$tcx` and `'tcx` interchangeably.
+// We should either not take `$tcx` at all and use `'tcx` everywhere, or use
+// `$tcx` everywhere (even if that isn't necessary due to lack of hygiene).
 macro_rules! define_queries_struct {
     (tcx: $tcx:tt,
      input: ($(([$($modifiers:tt)*] [$($attr:tt)*] [$name:ident]))*)) => {
@@ -494,8 +516,8 @@ macro_rules! define_queries_struct {
             /// `DepGraph::try_mark_green()` and the query infrastructure.
             pub(crate) on_disk_cache: OnDiskCache<'tcx>,
 
-            providers: IndexVec<CrateNum, Providers<$tcx>>,
-            fallback_extern_providers: Box<Providers<$tcx>>,
+            providers: IndexVec<CrateNum, Providers>,
+            fallback_extern_providers: Box<Providers>,
 
             $($(#[$attr])*  $name: QueryState<
                 TyCtxt<$tcx>,
@@ -505,8 +527,8 @@ macro_rules! define_queries_struct {
 
         impl<$tcx> Queries<$tcx> {
             pub(crate) fn new(
-                providers: IndexVec<CrateNum, Providers<$tcx>>,
-                fallback_extern_providers: Providers<$tcx>,
+                providers: IndexVec<CrateNum, Providers>,
+                fallback_extern_providers: Providers,
                 on_disk_cache: OnDiskCache<'tcx>,
             ) -> Self {
                 Queries {
@@ -539,11 +561,11 @@ macro_rules! define_queries_struct {
 macro_rules! define_provider_struct {
     (tcx: $tcx:tt,
      input: ($(([$($modifiers:tt)*] [$name:ident] [$K:ty] [$R:ty]))*)) => {
-        pub struct Providers<$tcx> {
-            $(pub $name: fn(TyCtxt<$tcx>, $K) -> $R,)*
+        pub struct Providers {
+            $(pub $name: for<$tcx> fn(TyCtxt<$tcx>, $K) -> $R,)*
         }
 
-        impl<$tcx> Default for Providers<$tcx> {
+        impl Default for Providers {
             fn default() -> Self {
                 $(fn $name<$tcx>(_: TyCtxt<$tcx>, key: $K) -> $R {
                     bug!("`tcx.{}({:?})` unsupported by its crate",

src/librustc_middle/util/bug.rs

@@ -47,6 +47,6 @@ pub fn trigger_delay_span_bug(tcx: TyCtxt<'_>, key: rustc_hir::def_id::DefId) {
     );
 }
 
-pub fn provide(providers: &mut crate::ty::query::Providers<'_>) {
+pub fn provide(providers: &mut crate::ty::query::Providers) {
     *providers = crate::ty::query::Providers { trigger_delay_span_bug, ..*providers };
 }

src/librustc_mir/borrow_check/mod.rs

@@ -86,7 +86,7 @@ crate struct Upvar {
 
 const DEREF_PROJECTION: &[PlaceElem<'_>; 1] = &[ProjectionElem::Deref];
 
-pub fn provide(providers: &mut Providers<'_>) {
+pub fn provide(providers: &mut Providers) {
     *providers = Providers { mir_borrowck, ..*providers };
 }
 

src/librustc_mir/const_eval/fn_queries.rs

@@ -156,7 +156,7 @@ fn const_fn_is_allowed_fn_ptr(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
         && tcx.lookup_const_stability(def_id).map(|stab| stab.allow_const_fn_ptr).unwrap_or(false)
 }
 
-pub fn provide(providers: &mut Providers<'_>) {
+pub fn provide(providers: &mut Providers) {
     *providers = Providers {
         is_const_fn_raw,
         is_const_impl_raw: |tcx, def_id| is_const_impl_raw(tcx, def_id.expect_local()),

src/librustc_mir/lib.rs

@@ -47,7 +47,7 @@ pub mod util;
 
 use rustc_middle::ty::query::Providers;
 
-pub fn provide(providers: &mut Providers<'_>) {
+pub fn provide(providers: &mut Providers) {
     borrow_check::provide(providers);
     const_eval::provide(providers);
     shim::provide(providers);