Rollup merge of #106797 - FawazTirmizi:dev/issues/104284, r=bjorn3

[rust.git] / compiler / rustc_borrowck / src / lib.rs

diff --git a/compiler/rustc_borrowck/src/lib.rs b/compiler/rustc_borrowck/src/lib.rs
index 168b798788b4c747c7fad8e4db5337b5f36fceaf..278ffed07477b5b3bdf8224a7b3c79c89b2b9ace 100644 (file)
--- a/compiler/rustc_borrowck/src/lib.rs
+++ b/compiler/rustc_borrowck/src/lib.rs
@@ -863,7 +863,6 @@ enum WriteKind {
 /// local place can be mutated.
 //
 // FIXME: @nikomatsakis suggested that this flag could be removed with the following modifications:
-// - Merge `check_access_permissions()` and `check_if_reassignment_to_immutable_state()`.
 // - Split `is_mutable()` into `is_assignable()` (can be directly assigned) and
 //   `is_declared_mutable()`.
 // - Take flow state into consideration in `is_assignable()` for local variables.
@@ -1132,20 +1131,6 @@ fn mutate_place(
         // Write of P[i] or *P requires P init'd.
         self.check_if_assigned_path_is_moved(location, place_span, flow_state);
 
-        // Special case: you can assign an immutable local variable
-        // (e.g., `x = ...`) so long as it has never been initialized
-        // before (at this point in the flow).
-        if let Some(local) = place_span.0.as_local() {
-            if let Mutability::Not = self.body.local_decls[local].mutability {
-                // check for reassignments to immutable local variables
-                self.check_if_reassignment_to_immutable_state(
-                    location, local, place_span, flow_state,
-                );
-                return;
-            }
-        }
-
-        // Otherwise, use the normal access permission rules.
         self.access_place(
             location,
             place_span,
@@ -1554,24 +1539,6 @@ fn check_activations(&mut self, location: Location, span: Span, flow_state: &Flo
         }
     }
 
-    fn check_if_reassignment_to_immutable_state(
-        &mut self,
-        location: Location,
-        local: Local,
-        place_span: (Place<'tcx>, Span),
-        flow_state: &Flows<'cx, 'tcx>,
-    ) {
-        debug!("check_if_reassignment_to_immutable_state({:?})", local);
-
-        // Check if any of the initializations of `local` have happened yet:
-        if let Some(init_index) = self.is_local_ever_initialized(local, flow_state) {
-            // And, if so, report an error.
-            let init = &self.move_data.inits[init_index];
-            let span = init.span(&self.body);
-            self.report_illegal_reassignment(location, place_span, span, place_span.0);
-        }
-    }
-
     fn check_if_full_path_is_moved(
         &mut self,
         location: Location,
@@ -2037,12 +2004,19 @@ fn check_access_permissions(
         // partial initialization, do not complain about mutability
         // errors except for actual mutation (as opposed to an attempt
         // to do a partial initialization).
-        let previously_initialized =
-            self.is_local_ever_initialized(place.local, flow_state).is_some();
+        let previously_initialized = self.is_local_ever_initialized(place.local, flow_state);
 
         // at this point, we have set up the error reporting state.
-        if previously_initialized {
-            self.report_mutability_error(place, span, the_place_err, error_access, location);
+        if let Some(init_index) = previously_initialized {
+            if let (AccessKind::Mutate, Some(_)) = (error_access, place.as_local()) {
+                // If this is a mutate access to an immutable local variable with no projections
+                // report the error as an illegal reassignment
+                let init = &self.move_data.inits[init_index];
+                let assigned_span = init.span(&self.body);
+                self.report_illegal_reassignment(location, (place, span), assigned_span, place);
+            } else {
+                self.report_mutability_error(place, span, the_place_err, error_access, location)
+            }
             true
         } else {
             false
@@ -2270,6 +2244,7 @@ pub struct BorrowckErrors<'tcx> {
         /// same primary span come out in a consistent order.
         buffered_move_errors:
             BTreeMap<Vec<MoveOutIndex>, (PlaceRef<'tcx>, DiagnosticBuilder<'tcx, ErrorGuaranteed>)>,
+        buffered_mut_errors: FxHashMap<Span, (DiagnosticBuilder<'tcx, ErrorGuaranteed>, usize)>,
         /// Diagnostics to be reported buffer.
         buffered: Vec<Diagnostic>,
         /// Set to Some if we emit an error during borrowck
@@ -2281,6 +2256,7 @@ pub fn new(tcx: TyCtxt<'tcx>) -> Self {
             BorrowckErrors {
                 tcx,
                 buffered_move_errors: BTreeMap::new(),
+                buffered_mut_errors: Default::default(),
                 buffered: Default::default(),
                 tainted_by_errors: None,
             }
@@ -2331,12 +2307,34 @@ pub fn buffer_move_error(
             }
         }
 
+        pub fn get_buffered_mut_error(
+            &mut self,
+            span: Span,
+        ) -> Option<(DiagnosticBuilder<'tcx, ErrorGuaranteed>, usize)> {
+            self.errors.buffered_mut_errors.remove(&span)
+        }
+
+        pub fn buffer_mut_error(
+            &mut self,
+            span: Span,
+            t: DiagnosticBuilder<'tcx, ErrorGuaranteed>,
+            count: usize,
+        ) {
+            self.errors.buffered_mut_errors.insert(span, (t, count));
+        }
+
         pub fn emit_errors(&mut self) -> Option<ErrorGuaranteed> {
             // Buffer any move errors that we collected and de-duplicated.
             for (_, (_, diag)) in std::mem::take(&mut self.errors.buffered_move_errors) {
                 // We have already set tainted for this error, so just buffer it.
                 diag.buffer(&mut self.errors.buffered);
             }
+            for (_, (mut diag, count)) in std::mem::take(&mut self.errors.buffered_mut_errors) {
+                if count > 10 {
+                    diag.note(&format!("...and {} other attempted mutable borrows", count - 10));
+                }
+                diag.buffer(&mut self.errors.buffered);
+            }
 
             if !self.errors.buffered.is_empty() {
                 self.errors.buffered.sort_by_key(|diag| diag.sort_span);