Make the borrow check mode an enum and update documentation

Author: 1c3t3a

compiler/rustc_mir_transform/src/check_alignment.rs

@@ -4,7 +4,7 @@ use rustc_middle::mir::*;
 use rustc_middle::ty::{Ty, TyCtxt};
 use rustc_session::Session;
 
-use crate::check_pointers::{PointerCheck, check_pointers};
+use crate::check_pointers::{BorrowCheckMode, PointerCheck, check_pointers};
 
 pub(super) struct CheckAlignment;
 
@@ -20,7 +20,13 @@ impl<'tcx> crate::MirPass<'tcx> for CheckAlignment {
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         // Skip trivially aligned place types.
         let excluded_pointees = [tcx.types.bool, tcx.types.i8, tcx.types.u8];
-        check_pointers(tcx, body, &excluded_pointees, insert_alignment_check, false);
+        check_pointers(
+            tcx,
+            body,
+            &excluded_pointees,
+            insert_alignment_check,
+            BorrowCheckMode::ExcludeBorrows,
+        );
     }
 }
 

compiler/rustc_mir_transform/src/check_null.rs

@@ -4,7 +4,7 @@ use rustc_middle::mir::*;
 use rustc_middle::ty::{Ty, TyCtxt};
 use rustc_session::Session;
 
-use crate::check_pointers::{PointerCheck, check_pointers};
+use crate::check_pointers::{BorrowCheckMode, PointerCheck, check_pointers};
 
 pub(super) struct CheckNull;
 
@@ -14,7 +14,7 @@ impl<'tcx> crate::MirPass<'tcx> for CheckNull {
     }
 
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
-        check_pointers(tcx, body, &[], insert_null_check, true);
+        check_pointers(tcx, body, &[], insert_null_check, BorrowCheckMode::IncludeBorrows);
     }
 }
 

compiler/rustc_mir_transform/src/check_pointers.rs

@@ -12,14 +12,24 @@ pub(crate) struct PointerCheck<'tcx> {
     pub(crate) assert_kind: Box<AssertKind<Operand<'tcx>>>,
 }
 
+/// Indicates whether we insert the checks for borrow places of a raw pointer.
+/// Concretely places with [MutatingUseContext::Borrow] or
+/// [NonMutatingUseContext::SharedBorrow].
+#[derive(Copy, Clone)]
+pub(crate) enum BorrowCheckMode {
+    IncludeBorrows,
+    ExcludeBorrows,
+}
+
 /// Utility for adding a check for read/write on every sized, raw pointer.
 ///
 /// Visits every read/write access to a [Sized], raw pointer and inserts a
 /// new basic block directly before the pointer access. (Read/write accesses
-/// are determined by the `PlaceContext` of the MIR visitor. In particular,
-/// uses of pointers in borrow expressions are *not* visited). Then calls
+/// are determined by the `PlaceContext` of the MIR visitor.) Then calls
 /// `on_finding` to insert the actual logic for a pointer check (e.g. check for
-/// alignment).
+/// alignment). A check can choose to be inserted for (mutable) borrows of
+/// raw pointers via the `borrow_check_mode` parameter.
+///
 /// This utility takes care of the right order of blocks, the only thing a
 /// caller must do in `on_finding` is:
 /// - Append [Statement]s to `stmts`.
@@ -35,7 +45,7 @@ pub(crate) fn check_pointers<'a, 'tcx, F>(
     body: &mut Body<'tcx>,
     excluded_pointees: &'a [Ty<'tcx>],
     on_finding: F,
-    check_for_borrows: bool,
+    borrow_check_mode: BorrowCheckMode,
 ) where
     F: Fn(
         /* tcx: */ TyCtxt<'tcx>,
@@ -72,7 +82,7 @@ pub(crate) fn check_pointers<'a, 'tcx, F>(
                 local_decls,
                 typing_env,
                 excluded_pointees,
-                check_for_borrows,
+                borrow_check_mode,
             );
             finder.visit_statement(statement, location);
 
@@ -117,7 +127,7 @@ struct PointerFinder<'a, 'tcx> {
     typing_env: ty::TypingEnv<'tcx>,
     pointers: Vec<(Place<'tcx>, Ty<'tcx>)>,
     excluded_pointees: &'a [Ty<'tcx>],
-    check_for_borrows: bool,
+    borrow_check_mode: BorrowCheckMode,
 }
 
 impl<'a, 'tcx> PointerFinder<'a, 'tcx> {
@@ -126,15 +136,15 @@ impl<'a, 'tcx> PointerFinder<'a, 'tcx> {
         local_decls: &'a mut LocalDecls<'tcx>,
         typing_env: ty::TypingEnv<'tcx>,
         excluded_pointees: &'a [Ty<'tcx>],
-        check_for_borrows: bool,
+        borrow_check_mode: BorrowCheckMode,
     ) -> Self {
         PointerFinder {
             tcx,
             local_decls,
             typing_env,
             excluded_pointees,
             pointers: Vec::new(),
-            check_for_borrows,
+            borrow_check_mode,
         }
     }
 
@@ -145,8 +155,6 @@ impl<'a, 'tcx> PointerFinder<'a, 'tcx> {
 
 impl<'a, 'tcx> Visitor<'tcx> for PointerFinder<'a, 'tcx> {
     fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, location: Location) {
-        // We want to only check reads and writes to Places, so we specifically exclude
-        // Borrow and RawBorrow.
         match context {
             PlaceContext::MutatingUse(
                 MutatingUseContext::Store
@@ -159,7 +167,7 @@ impl<'a, 'tcx> Visitor<'tcx> for PointerFinder<'a, 'tcx> {
             ) => {}
             PlaceContext::MutatingUse(MutatingUseContext::Borrow)
             | PlaceContext::NonMutatingUse(NonMutatingUseContext::SharedBorrow)
-                if self.check_for_borrows => {}
+                if matches!(self.borrow_check_mode, BorrowCheckMode::IncludeBorrows) => {}
             _ => {
                 return;
             }