Edition 2021 enables disjoint capture

Author: arora-aman

compiler/rustc_typeck/src/check/upvar.rs

@@ -177,7 +177,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         // We now fake capture information for all variables that are mentioned within the closure
         // We do this after handling migrations so that min_captures computes before
-        if !self.tcx.features().capture_disjoint_fields {
+        if !enable_precise_capture(self.tcx, span) {
             let mut capture_information: InferredCaptureInformation<'tcx> = Default::default();
 
             if let Some(upvars) = self.tcx.upvars_mentioned(closure_def_id) {
@@ -212,7 +212,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
             // If we have an origin, store it.
             if let Some(origin) = delegate.current_origin.clone() {
-                let origin = if self.tcx.features().capture_disjoint_fields {
+                let origin = if enable_precise_capture(self.tcx, span) {
                     (origin.0, restrict_capture_precision(origin.1))
                 } else {
                     (origin.0, Place { projections: vec![], ..origin.1 })
@@ -1924,3 +1924,13 @@ fn determine_place_ancestry_relation(
         PlaceAncestryRelation::Divergent
     }
 }
+
+/// Precise capture is enabled if the feature gate `capture_disjoint_fields` is enabled or if
+/// user is using Rust Edition 2021 or higher.
+///
+/// `span` is the span of the closure.
+fn enable_precise_capture(tcx: TyCtxt<'_>, span: Span) -> bool {
+    // We use span here to ensure that if the closure was generated by a macro with a different
+    // edition.
+    tcx.features().capture_disjoint_fields || span.rust_2021()
+}

src/test/ui/closures/2229_closure_analysis/run_pass/edition.rs

@@ -0,0 +1,23 @@
+// edition:2021
+// run-pass
+
+// Test that edition 2021 enables disjoint capture by default.
+
+struct Point {
+    x: i32,
+    y: i32,
+}
+
+fn main() {
+    let mut p = Point { x: 10, y: 10 };
+
+    let c = || {
+        println!("{}", p.x);
+    };
+
+    // `c` should only capture `p.x`, therefore mutating `p.y` is allowed.
+    let py = &mut p.y;
+
+    c();
+    *py = 20;
+}