Auto merge of rust-lang#88280 - sexxi-goose:non-exhaustive, r=nikomatsakis

Handle match statements with non exhaustive variants in closures

This PR ensures that the behavior for match statements with non exhaustive variants is the same inside and outside closures.

If we have a non-exhaustive SingleVariant which is defined in a different crate, then we should handle the case the same way we would handle a MultiVariant: borrow the match discriminant.

Closes rust-lang/project-rfc-2229#59
r? `@nikomatsakis`

Author: bors

compiler/rustc_typeck/src/expr_use_visitor.rs

@@ -15,7 +15,7 @@ use rustc_index::vec::Idx;
 use rustc_infer::infer::InferCtxt;
 use rustc_middle::hir::place::ProjectionKind;
 use rustc_middle::mir::FakeReadCause;
-use rustc_middle::ty::{self, adjustment, Ty, TyCtxt};
+use rustc_middle::ty::{self, adjustment, AdtKind, Ty, TyCtxt};
 use rustc_target::abi::VariantIdx;
 use std::iter;
 
@@ -845,5 +845,20 @@ fn delegate_consume<'a, 'tcx>(
 }
 
 fn is_multivariant_adt(ty: Ty<'tcx>) -> bool {
-    if let ty::Adt(def, _) = ty.kind() { def.variants.len() > 1 } else { false }
+    if let ty::Adt(def, _) = ty.kind() {
+        // Note that if a non-exhaustive SingleVariant is defined in another crate, we need
+        // to assume that more cases will be added to the variant in the future. This mean
+        // that we should handle non-exhaustive SingleVariant the same way we would handle
+        // a MultiVariant.
+        // If the variant is not local it must be defined in another crate.
+        let is_non_exhaustive = match def.adt_kind() {
+            AdtKind::Struct | AdtKind::Union => {
+                def.non_enum_variant().is_field_list_non_exhaustive()
+            }
+            AdtKind::Enum => def.is_variant_list_non_exhaustive(),
+        };
+        def.variants.len() > 1 || (!def.did.is_local() && is_non_exhaustive)
+    } else {
+        false
+    }
 }

src/test/ui/closures/2229_closure_analysis/match/auxiliary/match_non_exhaustive_lib.rs

@@ -0,0 +1,10 @@
+#[non_exhaustive]
+pub enum E1 {}
+
+#[non_exhaustive]
+pub enum E2 { A, B }
+
+#[non_exhaustive]
+pub enum E3 { C }
+
+pub enum E4 { D }

src/test/ui/closures/2229_closure_analysis/issue-87097.rs renamed to src/test/ui/closures/2229_closure_analysis/match/issue-87097.rs

@@ -0,0 +1,37 @@
+// edition:2021
+
+enum SingleVariant {
+    A
+}
+
+struct TestStruct {
+    x: i32,
+    y: i32,
+    z: i32,
+}
+
+fn edge_case_if() {
+    let sv = SingleVariant::A;
+    let condition = true;
+    // sv should not be captured as it is a SingleVariant
+    let _a = || {
+        match sv {
+            SingleVariant::A if condition => (),
+            _ => ()
+        }
+    };
+    let mut mut_sv = sv;
+    _a();
+
+    // ts should be captured
+    let ts = TestStruct { x: 1, y: 1, z: 1 };
+    let _b = || { match ts {
+        TestStruct{ x: 1, .. } => (),
+        _ => ()
+    }};
+    let mut mut_ts = ts;
+    //~^ ERROR: cannot move out of `ts` because it is borrowed
+    _b();
+}
+
+fn main() {}