Compute default query providers at compile-time

All of the `provide` functions are made `const`, allowing
us to compute the default local and extern query providers
entirely at compile-time.

In addition to moving runtime work to compile-time, this will
allow our internal documentation to show all query implementations,
once #87038 is implemented.

Author: Aaron1011

compiler/rustc_codegen_ssa/src/back/symbol_export.rs

@@ -357,7 +357,7 @@ fn is_unreachable_local_definition_provider(tcx: TyCtxt<'_>, def_id: LocalDefId)
     !tcx.reachable_set(()).contains(&def_id)
 }
 
-pub fn provide(providers: &mut Providers) {
+pub const 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;
@@ -367,7 +367,7 @@ pub fn provide(providers: &mut Providers) {
     providers.wasm_import_module_map = wasm_import_module_map;
 }
 
-pub fn provide_extern(providers: &mut Providers) {
+pub const 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;
 }

compiler/rustc_codegen_ssa/src/base.rs

@@ -849,7 +849,7 @@ impl CrateInfo {
     }
 }
 
-pub fn provide(providers: &mut Providers) {
+pub const fn provide(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.

compiler/rustc_codegen_ssa/src/lib.rs

@@ -5,6 +5,8 @@
 #![feature(in_band_lifetimes)]
 #![feature(nll)]
 #![feature(associated_type_bounds)]
+#![feature(const_fn_fn_ptr_basics)]
+#![feature(const_mut_refs)]
 #![recursion_limit = "256"]
 
 //! This crate contains codegen code that is used by all codegen backends (LLVM and others).
@@ -161,13 +163,13 @@ pub struct CodegenResults {
     pub crate_info: CrateInfo,
 }
 
-pub fn provide(providers: &mut Providers) {
+pub const fn provide(providers: &mut Providers) {
     crate::back::symbol_export::provide(providers);
     crate::base::provide(providers);
     crate::target_features::provide(providers);
 }
 
-pub fn provide_extern(providers: &mut Providers) {
+pub const fn provide_extern(providers: &mut Providers) {
     crate::back::symbol_export::provide_extern(providers);
 }
 

compiler/rustc_codegen_ssa/src/target_features.rs

@@ -245,7 +245,7 @@ pub fn supported_target_features(sess: &Session) -> &'static [(&'static str, Opt
     }
 }
 
-pub(crate) fn provide(providers: &mut Providers) {
+pub(crate) const fn provide(providers: &mut Providers) {
     providers.supported_target_features = |tcx, cnum| {
         assert_eq!(cnum, LOCAL_CRATE);
         if tcx.sess.opts.actually_rustdoc {

compiler/rustc_interface/src/lib.rs

@@ -1,5 +1,7 @@
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
+#![feature(const_fn_fn_ptr_basics)]
+#![feature(const_mut_refs)]
 #![feature(internal_output_capture)]
 #![feature(nll)]
 #![feature(once_cell)]

compiler/rustc_interface/src/passes.rs

@@ -45,7 +45,6 @@ use std::any::Any;
 use std::cell::RefCell;
 use std::ffi::OsString;
 use std::io::{self, BufWriter, Write};
-use std::lazy::SyncLazy;
 use std::marker::PhantomPinned;
 use std::path::PathBuf;
 use std::pin::Pin;
@@ -737,35 +736,35 @@ pub fn prepare_outputs(
     Ok(outputs)
 }
 
-pub static DEFAULT_QUERY_PROVIDERS: SyncLazy<Providers> = SyncLazy::new(|| {
-    let providers = &mut Providers::default();
+pub const DEFAULT_QUERY_PROVIDERS: Providers = {
+    let mut providers = Providers::default();
     providers.analysis = analysis;
-    proc_macro_decls::provide(providers);
-    plugin::build::provide(providers);
-    rustc_middle::hir::provide(providers);
-    mir::provide(providers);
-    mir_build::provide(providers);
-    rustc_privacy::provide(providers);
-    typeck::provide(providers);
-    ty::provide(providers);
-    traits::provide(providers);
-    rustc_passes::provide(providers);
-    rustc_resolve::provide(providers);
-    rustc_traits::provide(providers);
-    rustc_ty_utils::provide(providers);
-    rustc_metadata::provide(providers);
-    rustc_lint::provide(providers);
-    rustc_symbol_mangling::provide(providers);
-    rustc_codegen_ssa::provide(providers);
-    *providers
-});
-
-pub static DEFAULT_EXTERN_QUERY_PROVIDERS: SyncLazy<Providers> = SyncLazy::new(|| {
-    let mut extern_providers = *DEFAULT_QUERY_PROVIDERS;
+    proc_macro_decls::provide(&mut providers);
+    plugin::build::provide(&mut providers);
+    rustc_middle::hir::provide(&mut providers);
+    mir::provide(&mut providers);
+    mir_build::provide(&mut providers);
+    rustc_privacy::provide(&mut providers);
+    typeck::provide(&mut providers);
+    ty::provide(&mut providers);
+    traits::provide(&mut providers);
+    rustc_passes::provide(&mut providers);
+    rustc_resolve::provide(&mut providers);
+    rustc_traits::provide(&mut providers);
+    rustc_ty_utils::provide(&mut providers);
+    rustc_metadata::provide(&mut providers);
+    rustc_lint::provide(&mut providers);
+    rustc_symbol_mangling::provide(&mut providers);
+    rustc_codegen_ssa::provide(&mut providers);
+    providers
+};
+
+pub const DEFAULT_EXTERN_QUERY_PROVIDERS: Providers = {
+    let mut extern_providers = DEFAULT_QUERY_PROVIDERS;
     rustc_metadata::provide_extern(&mut extern_providers);
     rustc_codegen_ssa::provide_extern(&mut extern_providers);
     extern_providers
-});
+};
 
 pub struct QueryContext<'tcx> {
     gcx: &'tcx GlobalCtxt<'tcx>,
@@ -808,10 +807,10 @@ pub fn create_global_ctxt<'tcx>(
     let query_result_on_disk_cache = rustc_incremental::load_query_result_cache(sess);
 
     let codegen_backend = compiler.codegen_backend();
-    let mut local_providers = *DEFAULT_QUERY_PROVIDERS;
+    let mut local_providers = DEFAULT_QUERY_PROVIDERS;
     codegen_backend.provide(&mut local_providers);
 
-    let mut extern_providers = *DEFAULT_EXTERN_QUERY_PROVIDERS;
+    let mut extern_providers = DEFAULT_EXTERN_QUERY_PROVIDERS;
     codegen_backend.provide(&mut extern_providers);
     codegen_backend.provide_extern(&mut extern_providers);
 

compiler/rustc_interface/src/proc_macro_decls.rs

@@ -32,6 +32,6 @@ impl<'v> ItemLikeVisitor<'v> for Finder<'_> {
     fn visit_foreign_item(&mut self, _foreign_item: &hir::ForeignItem<'_>) {}
 }
 
-pub(crate) fn provide(providers: &mut Providers) {
+pub(crate) const fn provide(providers: &mut Providers) {
     *providers = Providers { proc_macro_decls_static, ..*providers };
 }

compiler/rustc_lint/src/levels.rs

@@ -698,6 +698,6 @@ impl<'tcx> intravisit::Visitor<'tcx> for LintLevelMapBuilder<'_, 'tcx> {
     }
 }
 
-pub fn provide(providers: &mut Providers) {
+pub const fn provide(providers: &mut Providers) {
     providers.lint_levels = lint_levels;
 }

compiler/rustc_lint/src/lib.rs

@@ -37,6 +37,8 @@
 #![feature(never_type)]
 #![feature(nll)]
 #![feature(control_flow_enum)]
+#![feature(const_fn_fn_ptr_basics)]
+#![feature(const_mut_refs)]
 #![recursion_limit = "256"]
 
 #[macro_use]
@@ -96,7 +98,7 @@ 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 const fn provide(providers: &mut Providers) {
     levels::provide(providers);
     *providers = Providers { lint_mod, ..*providers };
 }

compiler/rustc_metadata/src/lib.rs

@@ -8,6 +8,8 @@
 #![feature(min_specialization)]
 #![feature(try_blocks)]
 #![feature(never_type)]
+#![feature(const_fn_fn_ptr_basics)]
+#![feature(const_mut_refs)]
 #![recursion_limit = "256"]
 
 extern crate proc_macro;

compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs

@@ -30,7 +30,7 @@ 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(providers: &mut Providers) {
+        pub const fn provide_extern(providers: &mut Providers) {
             $(fn $name<$lt>(
                 $tcx: TyCtxt<$lt>,
                 def_id_arg: ty::query::query_keys::$name<$lt>,
@@ -235,7 +235,7 @@ provide! { <'tcx> tcx, def_id, other, cdata,
     expn_that_defined => { cdata.get_expn_that_defined(def_id.index, tcx.sess) }
 }
 
-pub fn provide(providers: &mut Providers) {
+pub const 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

compiler/rustc_middle/src/hir/mod.rs

@@ -129,7 +129,7 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 }
 
-pub fn provide(providers: &mut Providers) {
+pub const 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.local_def_id_to_hir_id(id)))

compiler/rustc_middle/src/lib.rs

@@ -49,6 +49,8 @@
 #![feature(iter_zip)]
 #![feature(thread_local_const_init)]
 #![feature(try_reserve)]
+#![feature(const_fn_fn_ptr_basics)]
+#![feature(const_mut_refs)]
 #![recursion_limit = "512"]
 
 #[macro_use]

compiler/rustc_middle/src/middle/limits.rs

@@ -18,7 +18,7 @@ use rustc_span::symbol::{sym, Symbol};
 
 use std::num::IntErrorKind;
 
-pub fn provide(providers: &mut ty::query::Providers) {
+pub const fn provide(providers: &mut ty::query::Providers) {
     providers.limits = |tcx, ()| Limits {
         recursion_limit: get_recursion_limit(tcx.hir().krate_attrs(), tcx.sess),
         move_size_limit: get_limit(tcx.hir().krate_attrs(), tcx.sess, sym::move_size_limit, 0),

compiler/rustc_middle/src/middle/mod.rs

@@ -33,6 +33,6 @@ pub mod region;
 pub mod resolve_lifetime;
 pub mod stability;
 
-pub fn provide(providers: &mut crate::ty::query::Providers) {
+pub const fn provide(providers: &mut crate::ty::query::Providers) {
     limits::provide(providers);
 }

compiler/rustc_middle/src/ty/context.rs

@@ -2819,7 +2819,7 @@ 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 const fn provide(providers: &mut ty::query::Providers) {
     providers.in_scope_traits_map = |tcx, id| tcx.hir_crate(()).trait_map.get(&id);
     providers.module_exports = |tcx, id| tcx.gcx.export_map.get(&id).map(|v| &v[..]);
     providers.crate_name = |tcx, id| {

compiler/rustc_middle/src/ty/erase_regions.rs

@@ -2,7 +2,7 @@ use crate::mir;
 use crate::ty::fold::{TypeFoldable, TypeFolder};
 use crate::ty::{self, Ty, TyCtxt, TypeFlags};
 
-pub(super) fn provide(providers: &mut ty::query::Providers) {
+pub(super) const fn provide(providers: &mut ty::query::Providers) {
     *providers = ty::query::Providers { erase_regions_ty, ..*providers };
 }
 

compiler/rustc_middle/src/ty/layout.rs

@@ -242,7 +242,7 @@ fn layout_raw<'tcx>(
     })
 }
 
-pub fn provide(providers: &mut ty::query::Providers) {
+pub const fn provide(providers: &mut ty::query::Providers) {
     *providers = ty::query::Providers { layout_raw, ..*providers };
 }
 

compiler/rustc_middle/src/ty/mod.rs

@@ -1978,7 +1978,7 @@ pub fn ast_uint_ty(uty: UintTy) -> ast::UintTy {
     }
 }
 
-pub fn provide(providers: &mut ty::query::Providers) {
+pub const fn provide(providers: &mut ty::query::Providers) {
     context::provide(providers);
     erase_regions::provide(providers);
     layout::provide(providers);

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -2348,6 +2348,6 @@ fn trimmed_def_paths(tcx: TyCtxt<'_>, (): ()) -> FxHashMap<DefId, Symbol> {
     map
 }
 
-pub fn provide(providers: &mut ty::query::Providers) {
+pub const fn provide(providers: &mut ty::query::Providers) {
     *providers = ty::query::Providers { trimmed_def_paths, ..*providers };
 }

compiler/rustc_middle/src/ty/query/mod.rs

@@ -215,8 +215,11 @@ macro_rules! define_callbacks {
             ) -> query_values::$name<'tcx>,)*
         }
 
-        impl Default for Providers {
-            fn default() -> Self {
+
+        // FIXME: Make this an `impl const Default for Providers`
+        // when `const_trait_impl` is no longer incomplete
+        impl Providers {
+            pub const fn default() -> Self {
                 Providers {
                     $($name: |_, key| bug!(
                         "`tcx.{}({:?})` unsupported by its crate; \

compiler/rustc_middle/src/ty/util.rs

@@ -1084,6 +1084,6 @@ pub fn normalize_opaque_types(
     val.fold_with(&mut visitor)
 }
 
-pub fn provide(providers: &mut ty::query::Providers) {
+pub const fn provide(providers: &mut ty::query::Providers) {
     *providers = ty::query::Providers { normalize_opaque_types, ..*providers }
 }

compiler/rustc_middle/src/util/bug.rs

@@ -48,6 +48,6 @@ pub fn trigger_delay_span_bug(tcx: TyCtxt<'_>, key: rustc_hir::def_id::DefId) {
     );
 }
 
-pub fn provide(providers: &mut crate::ty::query::Providers) {
+pub const fn provide(providers: &mut crate::ty::query::Providers) {
     *providers = crate::ty::query::Providers { trigger_delay_span_bug, ..*providers };
 }

compiler/rustc_mir/src/borrow_check/mod.rs

@@ -82,7 +82,7 @@ crate struct Upvar<'tcx> {
 
 const DEREF_PROJECTION: &[PlaceElem<'_>; 1] = &[ProjectionElem::Deref];
 
-pub fn provide(providers: &mut Providers) {
+pub const fn provide(providers: &mut Providers) {
     *providers = Providers {
         mir_borrowck: |tcx, did| {
             if let Some(def) = ty::WithOptConstParam::try_lookup(did, tcx) {

compiler/rustc_mir/src/const_eval/fn_queries.rs

@@ -102,7 +102,7 @@ fn is_promotable_const_fn(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
         }
 }
 
-pub fn provide(providers: &mut Providers) {
+pub const 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()),

compiler/rustc_mir/src/lib.rs

@@ -30,6 +30,8 @@ Rust MIR: a lowered representation of Rust.
 #![feature(once_cell)]
 #![feature(control_flow_enum)]
 #![feature(try_reserve)]
+#![feature(const_fn_fn_ptr_basics)]
+#![feature(const_mut_refs)]
 #![recursion_limit = "256"]
 
 #[macro_use]
@@ -48,7 +50,7 @@ pub mod util;
 
 use rustc_middle::ty::query::Providers;
 
-pub fn provide(providers: &mut Providers) {
+pub const fn provide(providers: &mut Providers) {
     borrow_check::provide(providers);
     const_eval::provide(providers);
     shim::provide(providers);

compiler/rustc_mir/src/monomorphize/partitioning/mod.rs

@@ -448,7 +448,7 @@ fn codegened_and_inlined_items<'tcx>(tcx: TyCtxt<'tcx>, (): ()) -> &'tcx DefIdSe
     tcx.arena.alloc(result)
 }
 
-pub fn provide(providers: &mut Providers) {
+pub const fn provide(providers: &mut Providers) {
     providers.collect_and_partition_mono_items = collect_and_partition_mono_items;
     providers.codegened_and_inlined_items = codegened_and_inlined_items;
 

compiler/rustc_mir/src/monomorphize/polymorphize.rs

@@ -23,7 +23,7 @@ use std::convert::TryInto;
 use std::ops::ControlFlow;
 
 /// Provide implementations of queries relating to polymorphization analysis.
-pub fn provide(providers: &mut Providers) {
+pub const fn provide(providers: &mut Providers) {
     providers.unused_generic_params = unused_generic_params;
 }
 

compiler/rustc_mir/src/shim.rs

@@ -23,7 +23,7 @@ use crate::util::elaborate_drops::{self, DropElaborator, DropFlagMode, DropStyle
 use crate::util::expand_aggregate;
 use crate::util::patch::MirPatch;
 
-pub fn provide(providers: &mut Providers) {
+pub const fn provide(providers: &mut Providers) {
     providers.mir_shims = make_shim;
 }
 

compiler/rustc_mir/src/transform/check_packed_ref.rs

@@ -9,7 +9,7 @@ use rustc_span::symbol::sym;
 use crate::transform::MirPass;
 use crate::util;
 
-pub(crate) fn provide(providers: &mut Providers) {
+pub(crate) const fn provide(providers: &mut Providers) {
     *providers = Providers { unsafe_derive_on_repr_packed, ..*providers };
 }