[analyzer] Don't crash with assertion failure on structured bindings

Proper modeling still remains to be done.
Note that BindingDecl#getHoldingVar() is almost always null, and this
should probably be handled by dealing with DecompositionDecl beforehand.

rdar://36852163

Differential Revision: https://reviews.llvm.org/D44183

llvm-svn: 326951

clang/lib/StaticAnalyzer/Core/ExprEngine.cpp

@@ -2463,7 +2463,12 @@ void ExprEngine::VisitCommonDeclRefExpr(const Expr *Ex, const NamedDecl *D,
                                           currBldrCtx->blockCount());
     state = state->assume(V.castAs<DefinedOrUnknownSVal>(), true);
     Bldr.generateNode(Ex, Pred, state->BindExpr(Ex, LCtx, V), nullptr,
-		      ProgramPoint::PostLValueKind);
+                      ProgramPoint::PostLValueKind);
+    return;
+  }
+  if (const auto* BD = dyn_cast<BindingDecl>(D)) {
+    // FIXME: proper support for bound declarations.
+    // For now, let's just prevent crashing.
     return;
   }
 

clang/test/Analysis/structured_bindings.cc

@@ -0,0 +1,10 @@
+// RUN: %clang_analyze_cc1 -std=c++17 -analyzer-checker=core -verify %s
+
+// expected-no-diagnostics
+struct s { int a; };
+int foo() {
+    auto[a] = s{1}; // FIXME: proper modelling
+    if (a) {
+    }
+}
+