Misc cleanups from reading some borrowck code

compiler/rustc_borrowck/src/lib.rs

@@ -1,4 +1,4 @@
-//! This query borrow-checks the MIR to (further) ensure it is not broken.
+//! This crate implemens MIR typeck and MIR borrowck.
 
 // tidy-alphabetical-start
 #![allow(internal_features)]
@@ -111,9 +111,9 @@ pub fn provide(providers: &mut Providers) {
     *providers = Providers { mir_borrowck, ..*providers };
 }
 
-/// Provider for `query mir_borrowck`. Similar to `typeck`, this must
-/// only be called for typeck roots which will then borrowck all
-/// nested bodies as well.
+/// Provider for `query mir_borrowck`. Unlike `typeck`, this must
+/// only be called for typeck roots which *similar* to `typeck` will
+/// then borrowck all nested bodies as well.
 fn mir_borrowck(
     tcx: TyCtxt<'_>,
     def: LocalDefId,

compiler/rustc_borrowck/src/root_cx.rs

@@ -255,7 +255,7 @@ impl<'tcx> BorrowCheckRootCtxt<'tcx> {
         }
 
         // We now apply the closure requirements of nested bodies modulo
-        // regions. In case a body does not depend on opaque types, we
+        // opaques. In case a body does not depend on opaque types, we
         // eagerly check its region constraints and use the final closure
         // requirements.
         //

compiler/rustc_borrowck/src/universal_regions.rs

@@ -1,13 +1,12 @@
 //! Code to extract the universally quantified regions declared on a
-//! function and the relationships between them. For example:
+//! function. For example:
 //!
 //! ```
 //! fn foo<'a, 'b, 'c: 'b>() { }
 //! ```
 //!
 //! here we would return a map assigning each of `{'a, 'b, 'c}`
-//! to an index, as well as the `FreeRegionMap` which can compute
-//! relationships between them.
+//! to an index.
 //!
 //! The code in this file doesn't *do anything* with those results; it
 //! just returns them for other code to use.
@@ -271,8 +270,7 @@ impl<'tcx> UniversalRegions<'tcx> {
     /// Creates a new and fully initialized `UniversalRegions` that
     /// contains indices for all the free regions found in the given
     /// MIR -- that is, all the regions that appear in the function's
-    /// signature. This will also compute the relationships that are
-    /// known between those regions.
+    /// signature.
     pub(crate) fn new(infcx: &BorrowckInferCtxt<'tcx>, mir_def: LocalDefId) -> Self {
         UniversalRegionsBuilder { infcx, mir_def }.build()
     }
@@ -648,10 +646,7 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
 
             BodyOwnerKind::Const { .. } | BodyOwnerKind::Static(..) => {
                 let identity_args = GenericArgs::identity_for_item(tcx, typeck_root_def_id);
-                if self.mir_def.to_def_id() == typeck_root_def_id
-                    // Do not ICE when checking default_field_values consts with lifetimes (#135649)
-                    && DefKind::Field != tcx.def_kind(tcx.parent(typeck_root_def_id))
-                {
+                if self.mir_def.to_def_id() == typeck_root_def_id {
                     let args = self.infcx.replace_free_regions_with_nll_infer_vars(
                         NllRegionVariableOrigin::FreeRegion,
                         identity_args,
@@ -699,30 +694,14 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
         let tcx = self.infcx.tcx;
         let typeck_root_def_id = tcx.typeck_root_def_id(self.mir_def.to_def_id());
         let identity_args = GenericArgs::identity_for_item(tcx, typeck_root_def_id);
-        let fr_args = match defining_ty {
-            DefiningTy::Closure(_, args)
-            | DefiningTy::CoroutineClosure(_, args)
-            | DefiningTy::Coroutine(_, args)
-            | DefiningTy::InlineConst(_, args) => {
-                // In the case of closures, we rely on the fact that
-                // the first N elements in the ClosureArgs are
-                // inherited from the `typeck_root_def_id`.
-                // Therefore, when we zip together (below) with
-                // `identity_args`, we will get only those regions
-                // that correspond to early-bound regions declared on
-                // the `typeck_root_def_id`.
-                assert!(args.len() >= identity_args.len());
-                assert_eq!(args.regions().count(), identity_args.regions().count());
-                args
-            }
-
-            DefiningTy::FnDef(_, args) | DefiningTy::Const(_, args) => args,
-
-            DefiningTy::GlobalAsm(_) => ty::List::empty(),
-        };
+        let renumbered_args = defining_ty.args();
 
         let global_mapping = iter::once((tcx.lifetimes.re_static, fr_static));
-        let arg_mapping = iter::zip(identity_args.regions(), fr_args.regions().map(|r| r.as_var()));
+        // This relies on typeck roots being generics_of parents with their
+        // parameters at the start of nested bodies' generics.
+        assert!(renumbered_args.len() >= identity_args.len());
+        let arg_mapping =
+            iter::zip(identity_args.regions(), renumbered_args.regions().map(|r| r.as_var()));
 
         UniversalRegionIndices {
             indices: global_mapping.chain(arg_mapping).collect(),
@@ -862,8 +841,8 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
         };
 
         // FIXME(#129952): We probably want a more principled approach here.
-        if let Err(terr) = inputs_and_output.skip_binder().error_reported() {
-            self.infcx.set_tainted_by_errors(terr);
+        if let Err(e) = inputs_and_output.error_reported() {
+            self.infcx.set_tainted_by_errors(e);
         }
 
         inputs_and_output

compiler/rustc_hir_analysis/src/collect/type_of.rs

@@ -10,92 +10,15 @@ use rustc_middle::ty::util::IntTypeExt;
 use rustc_middle::ty::{self, DefiningScopeKind, IsSuggestable, Ty, TyCtxt, TypeVisitableExt};
 use rustc_middle::{bug, span_bug};
 use rustc_span::{DUMMY_SP, Ident, Span};
+use tracing::instrument;
 
 use super::{HirPlaceholderCollector, ItemCtxt, bad_placeholder};
 use crate::check::wfcheck::check_static_item;
 use crate::hir_ty_lowering::HirTyLowerer;
 
 mod opaque;
 
-fn anon_const_type_of<'tcx>(icx: &ItemCtxt<'tcx>, def_id: LocalDefId) -> Ty<'tcx> {
-    use hir::*;
-    use rustc_middle::ty::Ty;
-    let tcx = icx.tcx;
-    let hir_id = tcx.local_def_id_to_hir_id(def_id);
-
-    let node = tcx.hir_node(hir_id);
-    let Node::AnonConst(&AnonConst { span, .. }) = node else {
-        span_bug!(
-            tcx.def_span(def_id),
-            "expected anon const in `anon_const_type_of`, got {node:?}"
-        );
-    };
-
-    let parent_node_id = tcx.parent_hir_id(hir_id);
-    let parent_node = tcx.hir_node(parent_node_id);
-
-    match parent_node {
-        // Anon consts "inside" the type system.
-        Node::ConstArg(&ConstArg {
-            hir_id: arg_hir_id,
-            kind: ConstArgKind::Anon(&AnonConst { hir_id: anon_hir_id, .. }),
-            ..
-        }) if anon_hir_id == hir_id => const_arg_anon_type_of(icx, arg_hir_id, span),
-
-        Node::Variant(Variant { disr_expr: Some(e), .. }) if e.hir_id == hir_id => {
-            tcx.adt_def(tcx.hir_get_parent_item(hir_id)).repr().discr_type().to_ty(tcx)
-        }
-
-        Node::Field(&hir::FieldDef { default: Some(c), def_id: field_def_id, .. })
-            if c.hir_id == hir_id =>
-        {
-            tcx.type_of(field_def_id).instantiate_identity()
-        }
-
-        _ => Ty::new_error_with_message(
-            tcx,
-            span,
-            format!("unexpected anon const parent in type_of(): {parent_node:?}"),
-        ),
-    }
-}
-
-fn const_arg_anon_type_of<'tcx>(icx: &ItemCtxt<'tcx>, arg_hir_id: HirId, span: Span) -> Ty<'tcx> {
-    use hir::*;
-    use rustc_middle::ty::Ty;
-
-    let tcx = icx.tcx;
-
-    match tcx.parent_hir_node(arg_hir_id) {
-        // Array length const arguments do not have `type_of` fed as there is never a corresponding
-        // generic parameter definition.
-        Node::Ty(&hir::Ty { kind: TyKind::Array(_, ref constant), .. })
-        | Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
-            if constant.hir_id == arg_hir_id =>
-        {
-            tcx.types.usize
-        }
-
-        Node::TyPat(pat) => {
-            let node = match tcx.parent_hir_node(pat.hir_id) {
-                // Or patterns can be nested one level deep
-                Node::TyPat(p) => tcx.parent_hir_node(p.hir_id),
-                other => other,
-            };
-            let hir::TyKind::Pat(ty, _) = node.expect_ty().kind else { bug!() };
-            icx.lower_ty(ty)
-        }
-
-        // This is not a `bug!` as const arguments in path segments that did not resolve to anything
-        // will result in `type_of` never being fed.
-        _ => Ty::new_error_with_message(
-            tcx,
-            span,
-            "`type_of` called on const argument's anon const before the const argument was lowered",
-        ),
-    }
-}
-
+#[instrument(level = "debug", skip(tcx), ret)]
 pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<'_, Ty<'_>> {
     use rustc_hir::*;
     use rustc_middle::ty::Ty;
@@ -408,6 +331,85 @@ pub(super) fn type_of_opaque_hir_typeck(
     }
 }
 
+fn anon_const_type_of<'tcx>(icx: &ItemCtxt<'tcx>, def_id: LocalDefId) -> Ty<'tcx> {
+    use hir::*;
+    use rustc_middle::ty::Ty;
+    let tcx = icx.tcx;
+    let hir_id = tcx.local_def_id_to_hir_id(def_id);
+
+    let node = tcx.hir_node(hir_id);
+    let Node::AnonConst(&AnonConst { span, .. }) = node else {
+        span_bug!(
+            tcx.def_span(def_id),
+            "expected anon const in `anon_const_type_of`, got {node:?}"
+        );
+    };
+
+    let parent_node_id = tcx.parent_hir_id(hir_id);
+    let parent_node = tcx.hir_node(parent_node_id);
+
+    match parent_node {
+        // Anon consts "inside" the type system.
+        Node::ConstArg(&ConstArg {
+            hir_id: arg_hir_id,
+            kind: ConstArgKind::Anon(&AnonConst { hir_id: anon_hir_id, .. }),
+            ..
+        }) if anon_hir_id == hir_id => const_arg_anon_type_of(icx, arg_hir_id, span),
+
+        Node::Variant(Variant { disr_expr: Some(e), .. }) if e.hir_id == hir_id => {
+            tcx.adt_def(tcx.hir_get_parent_item(hir_id)).repr().discr_type().to_ty(tcx)
+        }
+
+        Node::Field(&hir::FieldDef { default: Some(c), def_id: field_def_id, .. })
+            if c.hir_id == hir_id =>
+        {
+            tcx.type_of(field_def_id).instantiate_identity()
+        }
+
+        _ => Ty::new_error_with_message(
+            tcx,
+            span,
+            format!("unexpected anon const parent in type_of(): {parent_node:?}"),
+        ),
+    }
+}
+
+fn const_arg_anon_type_of<'tcx>(icx: &ItemCtxt<'tcx>, arg_hir_id: HirId, span: Span) -> Ty<'tcx> {
+    use hir::*;
+    use rustc_middle::ty::Ty;
+
+    let tcx = icx.tcx;
+
+    match tcx.parent_hir_node(arg_hir_id) {
+        // Array length const arguments do not have `type_of` fed as there is never a corresponding
+        // generic parameter definition.
+        Node::Ty(&hir::Ty { kind: TyKind::Array(_, ref constant), .. })
+        | Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
+            if constant.hir_id == arg_hir_id =>
+        {
+            tcx.types.usize
+        }
+
+        Node::TyPat(pat) => {
+            let node = match tcx.parent_hir_node(pat.hir_id) {
+                // Or patterns can be nested one level deep
+                Node::TyPat(p) => tcx.parent_hir_node(p.hir_id),
+                other => other,
+            };
+            let hir::TyKind::Pat(ty, _) = node.expect_ty().kind else { bug!() };
+            icx.lower_ty(ty)
+        }
+
+        // This is not a `bug!` as const arguments in path segments that did not resolve to anything
+        // will result in `type_of` never being fed.
+        _ => Ty::new_error_with_message(
+            tcx,
+            span,
+            "`type_of` called on const argument's anon const before the const argument was lowered",
+        ),
+    }
+}
+
 fn infer_placeholder_type<'tcx>(
     cx: &dyn HirTyLowerer<'tcx>,
     def_id: LocalDefId,