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Under -std=c++20 with use of consteval, the subexpression hierarchy sometimes
contains ConstantExpr nodes that getConversionFunction did not expect.
CastExpr::getConversionFunction is very rarely used, so this was difficult to
trigger in the compiler. It is possible to reproduce using -ast-dump=json, which
triggers an assertion for inputs with consteval implicit casts.
In AST-based tools, however, it surfaces quite easily if they try to inspect the
conversion function of a visited CastExpr.
Add two new testcases, both for implicit constructor conversions and
user-defined conversions with consteval.
Depends on D117390 <https://reviews.llvm.org/D117390>
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D117391
Files:
clang/lib/AST/Expr.cpp
clang/unittests/Tooling/CastExprTest.cpp
Index: clang/unittests/Tooling/CastExprTest.cpp
===================================================================
--- clang/unittests/Tooling/CastExprTest.cpp
+++ clang/unittests/Tooling/CastExprTest.cpp
@@ -14,12 +14,19 @@
struct CastExprVisitor : TestVisitor<CastExprVisitor> {
std::function<void(ExplicitCastExpr *)> OnExplicitCast;
+ std::function<void(CastExpr *)> OnCast;
bool VisitExplicitCastExpr(ExplicitCastExpr *Expr) {
if (OnExplicitCast)
OnExplicitCast(Expr);
return true;
}
+
+ bool VisitCastExpr(CastExpr *Expr) {
+ if (OnCast)
+ OnCast(Expr);
+ return true;
+ }
};
TEST(CastExprTest, GetSubExprAsWrittenThroughMaterializedTemporary) {
@@ -54,4 +61,57 @@
CastExprVisitor::Lang_CXX2a);
}
+// Verify that getConversionFunction looks through a ConstantExpr for implicit
+// constructor conversions (https://github.com/llvm/llvm-project/issues/53044):
+//
+// `-ImplicitCastExpr 'S' <ConstructorConversion>
+// `-ConstantExpr 'S'
+// |-value: Struct
+// `-CXXConstructExpr 'S' 'void (const char *)'
+// `-ImplicitCastExpr 'const char *' <ArrayToPointerDecay>
+// `-StringLiteral 'const char [7]' lvalue "foobar"
+TEST(CastExprTest, GetCtorConversionFunctionThroughConstantExpr) {
+ CastExprVisitor Visitor;
+ Visitor.OnCast = [](CastExpr *Expr) {
+ if (Expr->getCastKind() == CK_ConstructorConversion) {
+ auto *Conv = Expr->getConversionFunction();
+ EXPECT_TRUE(isa<CXXConstructorDecl>(Conv))
+ << "Expected CXXConstructorDecl, but saw " <<
Conv->getDeclKindName();
+ }
+ };
+ Visitor.runOver("struct X { consteval X(const char *) {} };\n"
+ "void f() { X x = \"foobar\"; }\n",
+ CastExprVisitor::Lang_CXX2a);
+}
+
+// Verify that getConversionFunction looks through a ConstantExpr for implicit
+// user-defined conversions.
+//
+// `-ImplicitCastExpr 'const char *' <UserDefinedConversion>
+// `-ConstantExpr 'const char *'
+// |-value: LValue
+// `-CXXMemberCallExpr 'const char *'
+// `-MemberExpr '<bound member function type>' .operator const char *
+// `-DeclRefExpr 'const X' lvalue Var 'x' 'const X'
+TEST(CastExprTest, GetUserDefinedConversionFunctionThroughConstantExpr) {
+ CastExprVisitor Visitor;
+ Visitor.OnCast = [](CastExpr *Expr) {
+ if (Expr->getCastKind() == CK_UserDefinedConversion) {
+ auto *Conv = Expr->getConversionFunction();
+ EXPECT_TRUE(isa<CXXMethodDecl>(Conv))
+ << "Expected CXXMethodDecl, but saw " << Conv->getDeclKindName();
+ }
+ };
+ Visitor.runOver("struct X {\n"
+ " consteval operator const char *() const {\n"
+ " return nullptr;\n"
+ " }\n"
+ "};\n"
+ "const char *f() {\n"
+ " constexpr X x;\n";
+ " return x;\n"
+ "}\n",
+ CastExprVisitor::Lang_CXX2a);
+}
+
} // namespace
Index: clang/lib/AST/Expr.cpp
===================================================================
--- clang/lib/AST/Expr.cpp
+++ clang/lib/AST/Expr.cpp
@@ -1944,6 +1944,7 @@
for (const CastExpr *E = this; E; E = dyn_cast<ImplicitCastExpr>(SubExpr)) {
SubExpr = skipImplicitTemporary(E->getSubExpr());
+ SubExpr = SubExpr->IgnoreImplicit();
if (E->getCastKind() == CK_ConstructorConversion)
return cast<CXXConstructExpr>(SubExpr)->getConstructor();
Index: clang/unittests/Tooling/CastExprTest.cpp
===================================================================
--- clang/unittests/Tooling/CastExprTest.cpp
+++ clang/unittests/Tooling/CastExprTest.cpp
@@ -14,12 +14,19 @@
struct CastExprVisitor : TestVisitor<CastExprVisitor> {
std::function<void(ExplicitCastExpr *)> OnExplicitCast;
+ std::function<void(CastExpr *)> OnCast;
bool VisitExplicitCastExpr(ExplicitCastExpr *Expr) {
if (OnExplicitCast)
OnExplicitCast(Expr);
return true;
}
+
+ bool VisitCastExpr(CastExpr *Expr) {
+ if (OnCast)
+ OnCast(Expr);
+ return true;
+ }
};
TEST(CastExprTest, GetSubExprAsWrittenThroughMaterializedTemporary) {
@@ -54,4 +61,57 @@
CastExprVisitor::Lang_CXX2a);
}
+// Verify that getConversionFunction looks through a ConstantExpr for implicit
+// constructor conversions (https://github.com/llvm/llvm-project/issues/53044):
+//
+// `-ImplicitCastExpr 'S' <ConstructorConversion>
+// `-ConstantExpr 'S'
+// |-value: Struct
+// `-CXXConstructExpr 'S' 'void (const char *)'
+// `-ImplicitCastExpr 'const char *' <ArrayToPointerDecay>
+// `-StringLiteral 'const char [7]' lvalue "foobar"
+TEST(CastExprTest, GetCtorConversionFunctionThroughConstantExpr) {
+ CastExprVisitor Visitor;
+ Visitor.OnCast = [](CastExpr *Expr) {
+ if (Expr->getCastKind() == CK_ConstructorConversion) {
+ auto *Conv = Expr->getConversionFunction();
+ EXPECT_TRUE(isa<CXXConstructorDecl>(Conv))
+ << "Expected CXXConstructorDecl, but saw " << Conv->getDeclKindName();
+ }
+ };
+ Visitor.runOver("struct X { consteval X(const char *) {} };\n"
+ "void f() { X x = \"foobar\"; }\n",
+ CastExprVisitor::Lang_CXX2a);
+}
+
+// Verify that getConversionFunction looks through a ConstantExpr for implicit
+// user-defined conversions.
+//
+// `-ImplicitCastExpr 'const char *' <UserDefinedConversion>
+// `-ConstantExpr 'const char *'
+// |-value: LValue
+// `-CXXMemberCallExpr 'const char *'
+// `-MemberExpr '<bound member function type>' .operator const char *
+// `-DeclRefExpr 'const X' lvalue Var 'x' 'const X'
+TEST(CastExprTest, GetUserDefinedConversionFunctionThroughConstantExpr) {
+ CastExprVisitor Visitor;
+ Visitor.OnCast = [](CastExpr *Expr) {
+ if (Expr->getCastKind() == CK_UserDefinedConversion) {
+ auto *Conv = Expr->getConversionFunction();
+ EXPECT_TRUE(isa<CXXMethodDecl>(Conv))
+ << "Expected CXXMethodDecl, but saw " << Conv->getDeclKindName();
+ }
+ };
+ Visitor.runOver("struct X {\n"
+ " consteval operator const char *() const {\n"
+ " return nullptr;\n"
+ " }\n"
+ "};\n"
+ "const char *f() {\n"
+ " constexpr X x;\n";
+ " return x;\n"
+ "}\n",
+ CastExprVisitor::Lang_CXX2a);
+}
+
} // namespace
Index: clang/lib/AST/Expr.cpp
===================================================================
--- clang/lib/AST/Expr.cpp
+++ clang/lib/AST/Expr.cpp
@@ -1944,6 +1944,7 @@
for (const CastExpr *E = this; E; E = dyn_cast<ImplicitCastExpr>(SubExpr)) {
SubExpr = skipImplicitTemporary(E->getSubExpr());
+ SubExpr = SubExpr->IgnoreImplicit();
if (E->getCastKind() == CK_ConstructorConversion)
return cast<CXXConstructExpr>(SubExpr)->getConstructor();
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