[OpenMP] Move unsupported structured bindings diagnostic (llvm#80216)

Move the diagnostic so it fires only when doing an OpenMP capture, not
for non-OpenMP captures. This allows non-OpenMP code to work when using
OpenMP elsewhere, such as the code reported in
llvm#66999.

Author: mikerice1969

clang/lib/Sema/SemaExpr.cpp

@@ -19528,16 +19528,6 @@ static bool captureInLambda(LambdaScopeInfo *LSI, ValueDecl *Var,
     ByRef = (LSI->ImpCaptureStyle == LambdaScopeInfo::ImpCap_LambdaByref);
   }
 
-  BindingDecl *BD = dyn_cast<BindingDecl>(Var);
-  // FIXME: We should support capturing structured bindings in OpenMP.
-  if (!Invalid && BD && S.LangOpts.OpenMP) {
-    if (BuildAndDiagnose) {
-      S.Diag(Loc, diag::err_capture_binding_openmp) << Var;
-      S.Diag(Var->getLocation(), diag::note_entity_declared_at) << Var;
-    }
-    Invalid = true;
-  }
-
   if (BuildAndDiagnose && S.Context.getTargetInfo().getTriple().isWasm() &&
       CaptureType.getNonReferenceType().isWebAssemblyReferenceType()) {
     S.Diag(Loc, diag::err_wasm_ca_reference) << 0;
@@ -19879,6 +19869,14 @@ bool Sema::tryCaptureVariable(
         // just break here. Similarly, global variables that are captured in a
         // target region should not be captured outside the scope of the region.
         if (RSI->CapRegionKind == CR_OpenMP) {
+          // FIXME: We should support capturing structured bindings in OpenMP.
+          if (isa<BindingDecl>(Var)) {
+            if (BuildAndDiagnose) {
+              Diag(ExprLoc, diag::err_capture_binding_openmp) << Var;
+              Diag(Var->getLocation(), diag::note_entity_declared_at) << Var;
+            }
+            return true;
+          }
           OpenMPClauseKind IsOpenMPPrivateDecl = isOpenMPPrivateDecl(
               Var, RSI->OpenMPLevel, RSI->OpenMPCaptureLevel);
           // If the variable is private (i.e. not captured) and has variably

clang/test/SemaCXX/decomposition-openmp.cpp

@@ -1,13 +1,32 @@
-
 // RUN: %clang_cc1 -fsyntax-only -verify -std=c++20 -fopenmp %s
 
-// FIXME: OpenMP should support capturing structured bindings
+// Okay, not an OpenMP capture.
 auto f() {
   int i[2] = {};
-  auto [a, b] = i; // expected-note 2{{declared here}}
+  auto [a, b] = i;
   return [=, &a] {
-    // expected-error@-1 {{capturing a structured binding is not yet supported in OpenMP}}
     return a + b;
-    // expected-error@-1 {{capturing a structured binding is not yet supported in OpenMP}}
   };
 }
+
+// Okay, not an OpenMP capture.
+void foo(int);
+void g() {
+  #pragma omp parallel
+  {
+    int i[2] = {};
+    auto [a, b] = i;
+    auto L = [&] { foo(a+b); };
+  }
+}
+
+// FIXME: OpenMP should support capturing structured bindings
+void h() {
+  int i[2] = {};
+  auto [a, b] = i; // expected-note 2{{declared here}}
+  #pragma omp parallel
+  {
+    // expected-error@+1 2{{capturing a structured binding is not yet supported in OpenMP}}
+    foo(a + b);
+  }
+}