Rollup merge of #161378 - nnethercote:FlowSensitiveAnalysis-cleanups, r=jackh726

`FlowSensitiveAnalysis` cleanups

Details in individual commits.

r? @cjgillot

Author: jhpratt

compiler/rustc_const_eval/src/check_consts/check.rs

@@ -49,91 +49,33 @@ pub(crate) struct Qualifs<'mir, 'tcx> {
 }
 
 impl<'mir, 'tcx> Qualifs<'mir, 'tcx> {
-    /// Returns `true` if `local` is `NeedsDrop` at the given `Location`.
-    ///
-    /// Only updates the cursor if absolutely necessary
-    pub(crate) fn needs_drop(
-        &mut self,
-        ccx: &'mir ConstCx<'mir, 'tcx>,
-        local: Local,
-        location: Location,
-    ) -> bool {
-        let ty = ccx.body.local_decls[local].ty;
-        // Peeking into opaque types causes cycles if the current function declares said opaque
-        // type. Thus we avoid short circuiting on the type and instead run the more expensive
-        // analysis that looks at the actual usage within this function
-        if !ty.has_opaque_types() && !NeedsDrop::in_any_value_of_ty(ccx, ty) {
-            return false;
-        }
-
-        let needs_drop = self.needs_drop.get_or_insert_with(|| {
-            let ConstCx { tcx, body, .. } = *ccx;
-
-            FlowSensitiveAnalysis::new(NeedsDrop, ccx)
-                .iterate_to_fixpoint(tcx, body, None)
-                .into_results_cursor(body)
-        });
-
-        needs_drop.seek_before_primary_effect(location);
-        needs_drop.get().contains(local)
-    }
-
-    /// Returns `true` if `local` is `NeedsNonConstDrop` at the given `Location`.
-    ///
-    /// Only updates the cursor if absolutely necessary
-    pub(crate) fn needs_non_const_drop(
-        &mut self,
-        ccx: &'mir ConstCx<'mir, 'tcx>,
-        local: Local,
-        location: Location,
-    ) -> bool {
-        let ty = ccx.body.local_decls[local].ty;
-        // Peeking into opaque types causes cycles if the current function declares said opaque
-        // type. Thus we avoid short circuiting on the type and instead run the more expensive
-        // analysis that looks at the actual usage within this function
-        if !ty.has_opaque_types() && !NeedsNonConstDrop::in_any_value_of_ty(ccx, ty) {
-            return false;
-        }
-
-        let needs_non_const_drop = self.needs_non_const_drop.get_or_insert_with(|| {
-            let ConstCx { tcx, body, .. } = *ccx;
-
-            FlowSensitiveAnalysis::new(NeedsNonConstDrop, ccx)
-                .iterate_to_fixpoint(tcx, body, None)
-                .into_results_cursor(body)
-        });
-
-        needs_non_const_drop.seek_before_primary_effect(location);
-        needs_non_const_drop.get().contains(local)
-    }
-
-    /// Returns `true` if `local` is `HasMutInterior` at the given `Location`.
+    /// Does `Q` hold for the `local` at the given `Location`?
     ///
     /// Only updates the cursor if absolutely necessary.
-    fn has_mut_interior(
-        &mut self,
+    fn in_local<Q: Qualif>(
+        qualif_results: &mut Option<QualifResults<'mir, 'tcx, Q>>,
         ccx: &'mir ConstCx<'mir, 'tcx>,
         local: Local,
         location: Location,
     ) -> bool {
         let ty = ccx.body.local_decls[local].ty;
         // Peeking into opaque types causes cycles if the current function declares said opaque
         // type. Thus we avoid short circuiting on the type and instead run the more expensive
-        // analysis that looks at the actual usage within this function
-        if !ty.has_opaque_types() && !HasMutInterior::in_any_value_of_ty(ccx, ty) {
+        // analysis that looks at the actual usage within this function.
+        if !ty.has_opaque_types() && !Q::in_any_value_of_ty(ccx, ty) {
             return false;
         }
 
-        let has_mut_interior = self.has_mut_interior.get_or_insert_with(|| {
+        let qualif_results = qualif_results.get_or_insert_with(|| {
             let ConstCx { tcx, body, .. } = *ccx;
 
-            FlowSensitiveAnalysis::new(HasMutInterior, ccx)
+            FlowSensitiveAnalysis::new(ccx)
                 .iterate_to_fixpoint(tcx, body, None)
                 .into_results_cursor(body)
         });
 
-        has_mut_interior.seek_before_primary_effect(location);
-        has_mut_interior.get().contains(local)
+        qualif_results.seek_before_primary_effect(location);
+        qualif_results.get().contains(local)
     }
 
     fn in_return_place(
@@ -161,9 +103,19 @@ impl<'mir, 'tcx> Qualifs<'mir, 'tcx> {
         let return_loc = ccx.body.terminator_loc(return_block);
 
         ConstQualifs {
-            needs_drop: self.needs_drop(ccx, RETURN_PLACE, return_loc),
-            needs_non_const_drop: self.needs_non_const_drop(ccx, RETURN_PLACE, return_loc),
-            has_mut_interior: self.has_mut_interior(ccx, RETURN_PLACE, return_loc),
+            needs_drop: Self::in_local(&mut self.needs_drop, ccx, RETURN_PLACE, return_loc),
+            needs_non_const_drop: Self::in_local(
+                &mut self.needs_non_const_drop,
+                ccx,
+                RETURN_PLACE,
+                return_loc,
+            ),
+            has_mut_interior: Self::in_local(
+                &mut self.has_mut_interior,
+                ccx,
+                RETURN_PLACE,
+                return_loc,
+            ),
             tainted_by_errors,
         }
     }
@@ -435,7 +387,7 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
         let ty_of_dropped_place = dropped_place.ty(self.body, self.tcx).ty;
 
         let needs_drop = if let Some(local) = dropped_place.as_local() {
-            self.qualifs.needs_drop(self.ccx, local, location)
+            Qualifs::in_local(&mut self.qualifs.needs_drop, self.ccx, local, location)
         } else {
             qualifs::NeedsDrop::in_any_value_of_ty(self.ccx, ty_of_dropped_place)
         };
@@ -448,7 +400,7 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
         let needs_non_const_drop = if let Some(local) = dropped_place.as_local() {
             // Use the span where the local was declared as the span of the drop error.
             err_span = self.body.local_decls[local].source_info.span;
-            self.qualifs.needs_non_const_drop(self.ccx, local, location)
+            Qualifs::in_local(&mut self.qualifs.needs_non_const_drop, self.ccx, local, location)
         } else {
             qualifs::NeedsNonConstDrop::in_any_value_of_ty(self.ccx, ty_of_dropped_place)
         };
@@ -602,7 +554,14 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
             | Rvalue::RawPtr(RawPtrKind::Const, place) => {
                 let borrowed_place_has_mut_interior = qualifs::in_place::<HasMutInterior, _>(
                     self.ccx,
-                    &mut |local| self.qualifs.has_mut_interior(self.ccx, local, location),
+                    &mut |local| {
+                        Qualifs::in_local(
+                            &mut self.qualifs.has_mut_interior,
+                            self.ccx,
+                            local,
+                            location,
+                        )
+                    },
                     place.as_ref(),
                 );
 

compiler/rustc_const_eval/src/check_consts/qualifs.rs

@@ -45,10 +45,10 @@ pub trait Qualif {
     const ANALYSIS_NAME: &'static str;
 
     /// Whether this `Qualif` is cleared when a local is moved from.
-    const IS_CLEARED_ON_MOVE: bool = false;
+    const IS_CLEARED_ON_MOVE: bool;
 
     /// Whether this `Qualif` might be evaluated after the promotion and can encounter a promoted.
-    const ALLOW_PROMOTED: bool = false;
+    const ALLOW_PROMOTED: bool;
 
     /// Extracts the field of `ConstQualifs` that corresponds to this `Qualif`.
     fn in_qualifs(qualifs: &ConstQualifs) -> bool;
@@ -79,6 +79,8 @@ pub struct HasMutInterior;
 
 impl Qualif for HasMutInterior {
     const ANALYSIS_NAME: &'static str = "flow_has_mut_interior";
+    const IS_CLEARED_ON_MOVE: bool = false;
+    const ALLOW_PROMOTED: bool = false;
 
     fn in_qualifs(qualifs: &ConstQualifs) -> bool {
         qualifs.has_mut_interior

compiler/rustc_const_eval/src/check_consts/resolver.rs

@@ -247,7 +247,7 @@ impl<'mir, 'tcx, Q> FlowSensitiveAnalysis<'mir, 'tcx, Q>
 where
     Q: Qualif,
 {
-    pub(super) fn new(_: Q, ccx: &'mir ConstCx<'mir, 'tcx>) -> Self {
+    pub(super) fn new(ccx: &'mir ConstCx<'mir, 'tcx>) -> Self {
         FlowSensitiveAnalysis { ccx, _qualif: PhantomData }
     }
 
@@ -309,7 +309,7 @@ impl<C> DebugWithContext<C> for State {
 
         if self.borrow != old.borrow {
             f.write_str("borrow: ")?;
-            self.qualif.fmt_diff_with(&old.borrow, ctxt, f)?;
+            self.borrow.fmt_diff_with(&old.borrow, ctxt, f)?;
             f.write_str("\n")?;
         }