[CFG] [analyzer] Add construction context when the constructor is treated like a functional cast.

[NoQ]

Summary

When a constructor with a single argument is treated as a functional cast expression, skip the functional cast while finding the construction context.

Like D43477, this patch only adds new construction contexts in cases where there is no destructor, which therefore has no immediate effect on the analyzer. It allows us to find the MaterializeTemporaryExpr in some extra cases, such as the newly added test with D &&d = D(1), which would help us with lifetime extension. But in case of lifetime extension through a normal lvalue reference, we'd also have to unwrap the no-op cast to const-object as well, which is something i'd follow up with.

lib/Analysis/CFG.cpp

if (const ConstructionContext *PreviousContext =
       // contexts within its parents.
       assert(PreviousContext->isStrictlyMoreSpecificThan(ContextSoFar) &&
              "Already within a different construction context!");
     } else {
       ConstructionContextMap[CE] = ContextSoFar;
     }
   } else if (auto *Cleanups = dyn_cast<ExprWithCleanups>(Child)) {
     findConstructionContexts(ContextSoFar, Cleanups->getSubExpr());
+  } else if (auto *Cast = dyn_cast<CXXFunctionalCastExpr>(Child)) {
+    findConstructionContexts(ContextSoFar, Cast->getSubExpr());
   } else if (auto *BTE = dyn_cast<CXXBindTemporaryExpr>(Child)) {
     findConstructionContexts(
         ConstructionContext::create(cfg->getBumpVectorContext(), BTE,
                                     ContextSoFar),
         BTE->getSubExpr());
   }
 }
 

test/Analysis/cfg-rich-constructors.cpp

 // CHECK-NEXT:     3: [B1.2]()
 // CHECK-NEXT:     4: [B1.3]
 // CHECK-NEXT:     5: [B1.4] (CXXConstructExpr, [B1.6], class C)
 // CHECK-NEXT:     6: C c = C::get();
 void simpleVariableInitializedByValue() {
   C c = C::get();
 }
 
-// TODO: Should find construction target for the three temporaries as well.
+// TODO: Should find construction target for the elidable constructors as well.
 // CHECK: void simpleVariableWithTernaryOperator(bool coin)
 // CHECK:        [B1]
 // CHECK-NEXT:     1: [B4.2] ? [B2.5] : [B3.6]
 // CHECK-NEXT:     2: [B1.1]
 // CHECK-NEXT:     3: [B1.2] (CXXConstructExpr, [B1.4], class C)
 // CHECK-NEXT:     4: C c = coin ? C::get() : C(0);
 // CHECK:        [B2]
 // CHECK-NEXT:     1: C::get
 // CHECK-NEXT:     2: [B2.1] (ImplicitCastExpr, FunctionToPointerDecay, class C (*)(void))
 // CHECK-NEXT:     3: [B2.2]()
 // CHECK-NEXT:     4: [B2.3]
 // CHECK-NEXT:     5: [B2.4] (CXXConstructExpr, class C)
 // CHECK:        [B3]
 // CHECK-NEXT:     1: 0
 // CHECK-NEXT:     2: [B3.1] (ImplicitCastExpr, NullToPointer, class C *)
-// CHECK-NEXT:     3: [B3.2] (CXXConstructExpr, class C)
+// CHECK-NEXT:     3: [B3.2] (CXXConstructExpr, [B3.5], class C)
 // CHECK-NEXT:     4: C([B3.3]) (CXXFunctionalCastExpr, ConstructorConversion, class C)
 // CHECK-NEXT:     5: [B3.4]
 // CHECK-NEXT:     6: [B3.5] (CXXConstructExpr, class C)
 // CHECK:        [B4]
 // CHECK-NEXT:     1: coin
 // CHECK-NEXT:     2: [B4.1] (ImplicitCastExpr, LValueToRValue, _Bool)
 // CHECK-NEXT:     T: [B4.2] ? ... : ...
 void simpleVariableWithTernaryOperator(bool coin) {
   C c = coin ? C::get() : C(0);
 }
 
+// CHECK: void simpleVariableWithElidableCopy()
+// CHECK:          1: 0
+// CHECK-NEXT:     2: [B1.1] (ImplicitCastExpr, NullToPointer, class C *)
+// CHECK-NEXT:     3: [B1.2] (CXXConstructExpr, [B1.5], class C)
+// CHECK-NEXT:     4: C([B1.3]) (CXXFunctionalCastExpr, ConstructorConversion, class C)
+// CHECK-NEXT:     5: [B1.4]
+// CHECK-NEXT:     6: [B1.5] (CXXConstructExpr, [B1.7], class C)
+// CHECK-NEXT:     7: C c = C(0);
+void simpleVariableWithElidableCopy() {
+  C c = C(0);
+}
+
 // CHECK: void referenceVariableWithConstructor()
 // CHECK:          1: 0
 // CHECK-NEXT:     2: [B1.1] (ImplicitCastExpr, NullToPointer, class C *)
 // CHECK-NEXT:     3: [B1.2] (CXXConstructExpr, [B1.4], const class C)
 // CHECK-NEXT:     4: [B1.3]
 // CHECK-NEXT:     5: const C &c(0);
 void referenceVariableWithConstructor() {
   const C &c(0);
 }
 
 // TODO: Should find construction target here.
 // CHECK: void referenceVariableWithInitializer()
 // CHECK:          1: C() (CXXConstructExpr, class C)
 // CHECK-NEXT:     2: [B1.1] (ImplicitCastExpr, NoOp, const class C)
 // CHECK-NEXT:     3: [B1.2]
 // CHECK-NEXT:     4: const C &c = C();
 void referenceVariableWithInitializer() {
   const C &c = C();
 }
 
-// TODO: Should find construction targets here.
+// TODO: Should find construction targets for the elidable constructors as well.
 // CHECK: void referenceVariableWithTernaryOperator(bool coin)
 // CHECK:        [B1]
 // CHECK-NEXT:     1: [B4.2] ? [B2.5] : [B3.6]
 // CHECK-NEXT:     2: [B1.1] (ImplicitCastExpr, NoOp, const class C)
 // CHECK-NEXT:     3: [B1.2]
 // CHECK-NEXT:     4: const C &c = coin ? C::get() : C(0);
 // CHECK:        [B2]
 // CHECK-NEXT:     1: C::get
 // CHECK-NEXT:     2: [B2.1] (ImplicitCastExpr, FunctionToPointerDecay, class C (*)(void))
 // CHECK-NEXT:     3: [B2.2]()
 // CHECK-NEXT:     4: [B2.3]
 // CHECK-NEXT:     5: [B2.4] (CXXConstructExpr, class C)
 // CHECK:        [B3]
 // CHECK-NEXT:     1: 0
 // CHECK-NEXT:     2: [B3.1] (ImplicitCastExpr, NullToPointer, class C *)
-// CHECK-NEXT:     3: [B3.2] (CXXConstructExpr, class C)
+// CHECK-NEXT:     3: [B3.2] (CXXConstructExpr, [B3.5], class C)
 // CHECK-NEXT:     4: C([B3.3]) (CXXFunctionalCastExpr, ConstructorConversion, class C)
 // CHECK-NEXT:     5: [B3.4]
 // CHECK-NEXT:     6: [B3.5] (CXXConstructExpr, class C)
 // CHECK:        [B4]
 // CHECK-NEXT:     1: coin
 // CHECK-NEXT:     2: [B4.1] (ImplicitCastExpr, LValueToRValue, _Bool)
 // CHECK-NEXT:     T: [B4.2] ? ... : ...
 void referenceVariableWithTernaryOperator(bool coin) {

 // CHECK:          1: C() (CXXConstructExpr, [B1.2], class C)
 // CHECK-NEXT:     2: [B1.1]
 // CHECK-NEXT:     3: [B1.2] (CXXConstructExpr, [B1.4], class C)
 // CHECK-NEXT:     4: return [B1.3];
 C returnTemporary() {
   return C();
 }
 
-// TODO: Should find construction targets for the first constructor as well.
 // CHECK: C returnTemporaryWithArgument()
 // CHECK:          1: nullptr
 // CHECK-NEXT:     2: [B1.1] (ImplicitCastExpr, NullToPointer, class C *)
-// CHECK-NEXT:     3: [B1.2] (CXXConstructExpr, class C)
+// CHECK-NEXT:     3: [B1.2] (CXXConstructExpr, [B1.5], class C)
 // CHECK-NEXT:     4: C([B1.3]) (CXXFunctionalCastExpr, ConstructorConversion, class C)
 // CHECK-NEXT:     5: [B1.4]
 // CHECK-NEXT:     6: [B1.5] (CXXConstructExpr, [B1.7], class C)
 // CHECK-NEXT:     7: return [B1.6];
 C returnTemporaryWithArgument() {
   return C(nullptr);
 }
 
 // CHECK: C returnTemporaryConstructedByFunction()
 // CHECK:          1: C::get
 // CHECK-NEXT:     2: [B1.1] (ImplicitCastExpr, FunctionToPointerDecay, class C (*)(void))
 // CHECK-NEXT:     3: [B1.2]()
 // CHECK-NEXT:     4: [B1.3]
 // CHECK-NEXT:     5: [B1.4] (CXXConstructExpr, [B1.6], class C)
 // CHECK-NEXT:     6: return [B1.5];
 C returnTemporaryConstructedByFunction() {
   return C::get();
 }
 
-// TODO: Should find construction targets for the first constructor as well.
 // CHECK: C returnChainOfCopies()
 // CHECK:          1: C::get
 // CHECK-NEXT:     2: [B1.1] (ImplicitCastExpr, FunctionToPointerDecay, class C (*)(void))
 // CHECK-NEXT:     3: [B1.2]()
 // CHECK-NEXT:     4: [B1.3]
-// CHECK-NEXT:     5: [B1.4] (CXXConstructExpr, class C)
+// CHECK-NEXT:     5: [B1.4] (CXXConstructExpr, [B1.7], class C)
 // CHECK-NEXT:     6: C([B1.5]) (CXXFunctionalCastExpr, ConstructorConversion, class C)
 // CHECK-NEXT:     7: [B1.6]
 // CHECK-NEXT:     8: [B1.7] (CXXConstructExpr, [B1.9], class C)
 // CHECK-NEXT:     9: return [B1.8];
 C returnChainOfCopies() {
   return C(C::get());
 }
 

 // CHECK-NEXT:     8: [B6.7] (BindTemporary)
 // CHECK:        [B7]
 // CHECK-NEXT:     1: coin
 // CHECK-NEXT:     2: [B7.1] (ImplicitCastExpr, LValueToRValue, _Bool)
 // CHECK-NEXT:     T: [B7.2] ? ... : ...
 void referenceVariableWithTernaryOperator(bool coin) {
   const D &d = coin ? D::get() : D(0);
 }
+
+// CHECK: void referenceWithFunctionalCast()
+// CHECK:          1: 1
+// CHECK-NEXT:     2: [B1.1] (CXXConstructExpr, [B1.3], [B1.5], class temporary_object_expr_with_dtors::D)
+// CHECK-NEXT:     3: [B1.2] (BindTemporary)
+// CHECK-NEXT:     4: temporary_object_expr_with_dtors::D([B1.3]) (CXXFunctionalCastExpr, ConstructorCon
+// CHECK-NEXT:     5: [B1.4]
+// CHECK-NEXT:     6: temporary_object_expr_with_dtors::D &&d = temporary_object_expr_with_dtors::D(1);
+// CHECK-NEXT:     7: [B1.6].~D() (Implicit destructor)
+void referenceWithFunctionalCast() {
+  D &&d = D(1);
+}
 } // end namespace temporary_object_expr_with_dtors