[SyntaxTree] Ignore implicit `CXXFunctionalCastExpr` wrapping constructor

Differential Revision: https://reviews.llvm.org/D87229

clang/lib/Tooling/Syntax/BuildTree.cpp

@@ -14,6 +14,7 @@
 #include "clang/AST/Expr.h"
 #include "clang/AST/ExprCXX.h"
 #include "clang/AST/IgnoreExpr.h"
+#include "clang/AST/OperationKinds.h"
 #include "clang/AST/RecursiveASTVisitor.h"
 #include "clang/AST/Stmt.h"
 #include "clang/AST/TypeLoc.h"
@@ -60,9 +61,25 @@ static Expr *IgnoreImplicitConstructorSingleStep(Expr *E) {
   return E;
 }
 
+// In:
+// struct X {
+//   X(int)
+// };
+// X x = X(1);
+// Ignores the implicit `CXXFunctionalCastExpr` that wraps
+// `CXXConstructExpr X(1)`.
+static Expr *IgnoreCXXFunctionalCastExprWrappingConstructor(Expr *E) {
+  if (auto *F = dyn_cast<CXXFunctionalCastExpr>(E)) {
+    if (F->getCastKind() == CK_ConstructorConversion)
+      return F->getSubExpr();
+  }
+  return E;
+}
+
 static Expr *IgnoreImplicit(Expr *E) {
   return IgnoreExprNodes(E, IgnoreImplicitSingleStep,
-                         IgnoreImplicitConstructorSingleStep);
+                         IgnoreImplicitConstructorSingleStep,
+                         IgnoreCXXFunctionalCastExprWrappingConstructor);
 }
 
 LLVM_ATTRIBUTE_UNUSED

clang/unittests/Tooling/Syntax/BuildTreeTest.cpp

@@ -4069,7 +4069,6 @@ struct X {
   X(int);
 };
 X test() {
-  // FIXME: Remove `UnknownExpression` due to implicit `CXXFunctionalCastExpr`
   [[return X(1);]]
 }
 )cpp",
@@ -4077,12 +4076,11 @@ X test() {
 ReturnStatement Statement
 |-'return' IntroducerKeyword
 |-UnknownExpression ReturnValue
-| `-UnknownExpression
-|   |-'X'
-|   |-'('
-|   |-IntegerLiteralExpression
-|   | `-'1' LiteralToken
-|   `-')'
+| |-'X'
+| |-'('
+| |-IntegerLiteralExpression
+| | `-'1' LiteralToken
+| `-')'
 `-';'
 )txt"}));
 }