[clang] [OpenMP] Support capturing structured bindings in OpenMP regions. (PR #190832)

[Alexey Bataev via cfe-commits]

================
@@ -4122,30 +4282,47 @@ class DSAAttrChecker final : public StmtVisitor<DSAAttrChecker, void> {
 
       if (isOpenMPTargetExecutionDirective(DKind) &&
           !Stack->isLoopControlVariable(VD).first) {
-        if (!Stack->checkMappableExprComponentListsForDecl(
-                VD, /*CurrentRegionOnly=*/true,
-                [this](OMPClauseMappableExprCommon::MappableExprComponentListRef
-                           StackComponents,
-                       OpenMPClauseKind) {
-                  if (SemaRef.LangOpts.OpenMP >= 50)
-                    return !StackComponents.empty();
-                  // Variable is used if it has been marked as an array, array
-                  // section, array shaping or the variable itself.
-                  return StackComponents.size() == 1 ||
-                         llvm::all_of(
-                             llvm::drop_begin(llvm::reverse(StackComponents)),
-                             [](const OMPClauseMappableExprCommon::
-                                    MappableComponent &MC) {
-                               return MC.getAssociatedDeclaration() ==
-                                          nullptr &&
-                                      (isa<ArraySectionExpr>(
-                                           MC.getAssociatedExpression()) ||
-                                       isa<OMPArrayShapingExpr>(
-                                           MC.getAssociatedExpression()) ||
-                                       isa<ArraySubscriptExpr>(
-                                           MC.getAssociatedExpression()));
-                             });
-                })) {
+        // Check if VD is already mapped. For DecompositionDecls, also check if
+        // the original variable they decompose has been mapped (via BindingDecl
+        // map clauses).
+        bool AlreadyMapped = Stack->checkMappableExprComponentListsForDecl(
+            VD, /*CurrentRegionOnly=*/true, [this](auto StackComponents, auto) {
+              if (SemaRef.LangOpts.OpenMP >= 50)
+                return !StackComponents.empty();
+              // Variable is used if it has been marked as an array, array
+              // section, array shaping or the variable itself.
+              return StackComponents.size() == 1 ||
+                     llvm::all_of(
+                         llvm::drop_begin(llvm::reverse(StackComponents)),
+                         [](const auto &MC) {
+                           return MC.getAssociatedDeclaration() == nullptr &&
+                                  (isa<ArraySectionExpr>(
+                                       MC.getAssociatedExpression()) ||
+                                   isa<OMPArrayShapingExpr>(
+                                       MC.getAssociatedExpression()) ||
+                                   isa<ArraySubscriptExpr>(
+                                       MC.getAssociatedExpression()));
+                         });
+            });
+
+        // For DecompositionDecls, check if the original variable has been
+        // mapped.
+        if (!AlreadyMapped && isa<DecompositionDecl>(VD)) {
+          if (const auto *DD = cast<DecompositionDecl>(VD)) {
----------------
alexey-bataev wrote:

```suggestion
        const auto *DD = dyn_cast<DecompositionDecl>(VD)
        if (!AlreadyMapped && DD) {
```

https://github.com/llvm/llvm-project/pull/190832