[clang] [Clang] Initializer list on RHS of assignment (PR #100548)

[via cfe-commits]

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@@ -14578,21 +14578,56 @@ ExprResult Sema::CreateBuiltinBinOp(SourceLocation OpLoc,
                                     BinaryOperatorKind Opc,
                                     Expr *LHSExpr, Expr *RHSExpr) {
   if (getLangOpts().CPlusPlus11 && isa<InitListExpr>(RHSExpr)) {
-    // The syntax only allows initializer lists on the RHS of assignment,
-    // so we don't need to worry about accepting invalid code for
-    // non-assignment operators.
-    // C++11 5.17p9:
-    //   The meaning of x = {v} [...] is that of x = T(v) [...]. The meaning
-    //   of x = {} is x = T().
-    InitializationKind Kind = InitializationKind::CreateDirectList(
-        RHSExpr->getBeginLoc(), RHSExpr->getBeginLoc(), RHSExpr->getEndLoc());
-    InitializedEntity Entity =
-        InitializedEntity::InitializeTemporary(LHSExpr->getType());
-    InitializationSequence InitSeq(*this, Entity, Kind, RHSExpr);
-    ExprResult Init = InitSeq.Perform(*this, Entity, Kind, RHSExpr);
-    if (Init.isInvalid())
-      return Init;
-    RHSExpr = Init.get();
+    // C++11 [expr.ass]p9, per CWG2768:
+    //   A braced-init-list B may appear on the right-hand side of
+    //    - an assignment to a scalar of type T, in which case the initializer
+    //      list shall have at most a single element. The meaning of x = B is
+    //      x = t, where t is an invented temporary variable declared and
+    //      initialized as T t = B.
+    switch (Opc) {
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cor3ntin wrote:

Using a switch here is not ideal.
There are only 3 cases we care about
- BO_Assign
- isAssignmentOp
- everything else

https://github.com/llvm/llvm-project/pull/100548