Quuxplusone created this revision.
Quuxplusone added reviewers: ldionne, rsmith, leonardchan, mizvekov.
Quuxplusone added a project: clang.
Quuxplusone requested review of this revision.
Herald added a subscriber: cfe-commits.
If this is a SFINAE context, then continuing to look up names (in particular,
to treat a non-function as a function, and then do ADL) might too-eagerly
complete a type that it's not safe to complete right now. We should just say
"okay, that's a substitution failure" and not do any more work than absolutely
required.
Fixes https://github.com/llvm/llvm-project/issues/52970
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D117603
Files:
clang/lib/Sema/Sema.cpp
clang/lib/Sema/SemaExprMember.cpp
clang/test/SemaCXX/PR52970.cpp
Index: clang/test/SemaCXX/PR52970.cpp
===================================================================
--- /dev/null
+++ clang/test/SemaCXX/PR52970.cpp
@@ -0,0 +1,59 @@
+// RUN: %clang_cc1 -fsyntax-only -std=c++11 -verify %s
+// RUN: %clang_cc1 -fsyntax-only -std=c++14 -verify %s
+// RUN: %clang_cc1 -fsyntax-only -std=c++17 -verify %s
+// RUN: %clang_cc1 -fsyntax-only -std=c++20 -verify %s
+// expected-no-diagnostics
+
+struct Incomplete;
+template<class T> struct Holder { T t; };
+
+namespace DotFollowingFunctionName {
+ struct Good {
+ struct Nested {
+ int b;
+ } a;
+ };
+
+ struct Bad {
+ Holder<Incomplete> a();
+ };
+
+ template<class T>
+ constexpr auto f(T t) -> decltype((t.a.b, true))
+ { return true; }
+ constexpr bool f(...) { return false; }
+
+ static_assert(DotFollowingFunctionName::f(Good{}), "");
+ static_assert(!DotFollowingFunctionName::f(Bad{}), "");
+
+#if __cplusplus >= 202002L
+ template<class T>
+ concept C = requires (T t) { t.a.b; };
+
+ static_assert(C<Good>);
+ static_assert(!C<Bad>);
+#endif
+}
+
+namespace DotFollowingPointer {
+ struct Good {
+ int begin();
+ };
+ using Bad = Holder<Incomplete>*;
+
+ template<class T>
+ constexpr auto f(T t) -> decltype((t.begin(), true))
+ { return true; }
+ constexpr bool f(...) { return false; }
+
+ static_assert(DotFollowingPointer::f(Good{}), "");
+ static_assert(!DotFollowingPointer::f(Bad{}), "");
+
+#if __cplusplus >= 202002L
+ template<class T>
+ concept C = requires (T t) { t.begin(); };
+
+ static_assert(C<Good>);
+ static_assert(!C<Bad>);
+#endif
+}
Index: clang/lib/Sema/SemaExprMember.cpp
===================================================================
--- clang/lib/Sema/SemaExprMember.cpp
+++ clang/lib/Sema/SemaExprMember.cpp
@@ -1645,6 +1645,9 @@
<< BaseType << int(IsArrow) << BaseExpr.get()->getSourceRange()
<< FixItHint::CreateReplacement(OpLoc, "->");
+ if (S.isSFINAEContext())
+ return ExprError();
+
// Recurse as an -> access.
IsArrow = true;
return LookupMemberExpr(S, R, BaseExpr, IsArrow, OpLoc, SS,
Index: clang/lib/Sema/Sema.cpp
===================================================================
--- clang/lib/Sema/Sema.cpp
+++ clang/lib/Sema/Sema.cpp
@@ -2552,6 +2552,10 @@
bool Sema::tryToRecoverWithCall(ExprResult &E, const PartialDiagnostic &PD,
bool ForceComplain,
bool (*IsPlausibleResult)(QualType)) {
+ if (isSFINAEContext()) {
+ // If this is a SFINAE context, don't try anything that might trigger ADL
prematurely.
+ return false;
+ }
SourceLocation Loc = E.get()->getExprLoc();
SourceRange Range = E.get()->getSourceRange();
Index: clang/test/SemaCXX/PR52970.cpp
===================================================================
--- /dev/null
+++ clang/test/SemaCXX/PR52970.cpp
@@ -0,0 +1,59 @@
+// RUN: %clang_cc1 -fsyntax-only -std=c++11 -verify %s
+// RUN: %clang_cc1 -fsyntax-only -std=c++14 -verify %s
+// RUN: %clang_cc1 -fsyntax-only -std=c++17 -verify %s
+// RUN: %clang_cc1 -fsyntax-only -std=c++20 -verify %s
+// expected-no-diagnostics
+
+struct Incomplete;
+template<class T> struct Holder { T t; };
+
+namespace DotFollowingFunctionName {
+ struct Good {
+ struct Nested {
+ int b;
+ } a;
+ };
+
+ struct Bad {
+ Holder<Incomplete> a();
+ };
+
+ template<class T>
+ constexpr auto f(T t) -> decltype((t.a.b, true))
+ { return true; }
+ constexpr bool f(...) { return false; }
+
+ static_assert(DotFollowingFunctionName::f(Good{}), "");
+ static_assert(!DotFollowingFunctionName::f(Bad{}), "");
+
+#if __cplusplus >= 202002L
+ template<class T>
+ concept C = requires (T t) { t.a.b; };
+
+ static_assert(C<Good>);
+ static_assert(!C<Bad>);
+#endif
+}
+
+namespace DotFollowingPointer {
+ struct Good {
+ int begin();
+ };
+ using Bad = Holder<Incomplete>*;
+
+ template<class T>
+ constexpr auto f(T t) -> decltype((t.begin(), true))
+ { return true; }
+ constexpr bool f(...) { return false; }
+
+ static_assert(DotFollowingPointer::f(Good{}), "");
+ static_assert(!DotFollowingPointer::f(Bad{}), "");
+
+#if __cplusplus >= 202002L
+ template<class T>
+ concept C = requires (T t) { t.begin(); };
+
+ static_assert(C<Good>);
+ static_assert(!C<Bad>);
+#endif
+}
Index: clang/lib/Sema/SemaExprMember.cpp
===================================================================
--- clang/lib/Sema/SemaExprMember.cpp
+++ clang/lib/Sema/SemaExprMember.cpp
@@ -1645,6 +1645,9 @@
<< BaseType << int(IsArrow) << BaseExpr.get()->getSourceRange()
<< FixItHint::CreateReplacement(OpLoc, "->");
+ if (S.isSFINAEContext())
+ return ExprError();
+
// Recurse as an -> access.
IsArrow = true;
return LookupMemberExpr(S, R, BaseExpr, IsArrow, OpLoc, SS,
Index: clang/lib/Sema/Sema.cpp
===================================================================
--- clang/lib/Sema/Sema.cpp
+++ clang/lib/Sema/Sema.cpp
@@ -2552,6 +2552,10 @@
bool Sema::tryToRecoverWithCall(ExprResult &E, const PartialDiagnostic &PD,
bool ForceComplain,
bool (*IsPlausibleResult)(QualType)) {
+ if (isSFINAEContext()) {
+ // If this is a SFINAE context, don't try anything that might trigger ADL prematurely.
+ return false;
+ }
SourceLocation Loc = E.get()->getExprLoc();
SourceRange Range = E.get()->getSourceRange();
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