fix: consider assignee expressions in record fields exhaustiveness check

Author: lowr

src/tools/rust-analyzer/crates/hir-ty/src/diagnostics/expr.rs

@@ -305,7 +305,10 @@ pub fn record_literal_missing_fields(
     expr: &Expr,
 ) -> Option<(VariantId, Vec<LocalFieldId>, /*exhaustive*/ bool)> {
     let (fields, exhaustive) = match expr {
-        Expr::RecordLit { fields, spread, .. } => (fields, spread.is_none()),
+        Expr::RecordLit { fields, spread, ellipsis, is_assignee_expr, .. } => {
+            let exhaustive = if *is_assignee_expr { !*ellipsis } else { spread.is_none() };
+            (fields, exhaustive)
+        }
         _ => return None,
     };
 

src/tools/rust-analyzer/crates/ide-diagnostics/src/handlers/missing_fields.rs

@@ -292,6 +292,37 @@ fn x(a: S) {
         )
     }
 
+    #[test]
+    fn missing_record_expr_in_assignee_expr() {
+        check_diagnostics(
+            r"
+struct S { s: usize, t: usize }
+struct S2 { s: S, t: () }
+struct T(S);
+fn regular(a: S) {
+    let s;
+    S { s, .. } = a;
+}
+fn nested(a: S2) {
+    let s;
+    S2 { s: S { s, .. }, .. } = a;
+}
+fn in_tuple(a: (S,)) {
+    let s;
+    (S { s, .. },) = a;
+}
+fn in_array(a: [S;1]) {
+    let s;
+    [S { s, .. },] = a;
+}
+fn in_tuple_struct(a: T) {
+    let s;
+    T(S { s, .. }) = a;
+}
+            ",
+        );
+    }
+
     #[test]
     fn range_mapping_out_of_macros() {
         check_fix(