[clang] c0185ff - [clang] Don't typo-fix an expression in a SFINAE context.
Arthur O'Dwyer via cfe-commits
cfe-commits at lists.llvm.org
Tue Feb 1 12:17:40 PST 2022
Author: Arthur O'Dwyer
Date: 2022-02-01T15:17:28-05:00
New Revision: c0185ffaec3cb0aa7677b13a898eaa485ef29421
URL: https://github.com/llvm/llvm-project/commit/c0185ffaec3cb0aa7677b13a898eaa485ef29421
DIFF: https://github.com/llvm/llvm-project/commit/c0185ffaec3cb0aa7677b13a898eaa485ef29421.diff
LOG: [clang] Don't typo-fix an expression in a SFINAE context.
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 #52970.
Differential Revision: https://reviews.llvm.org/D117603
Added:
clang/test/SemaTemplate/pr52970.cpp
Modified:
clang/lib/Sema/Sema.cpp
clang/lib/Sema/SemaExprMember.cpp
Removed:
################################################################################
diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
index a5a62276043d..7b57c8da4e9c 100644
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -2556,32 +2556,36 @@ bool Sema::tryToRecoverWithCall(ExprResult &E, const PartialDiagnostic &PD,
bool (*IsPlausibleResult)(QualType)) {
SourceLocation Loc = E.get()->getExprLoc();
SourceRange Range = E.get()->getSourceRange();
-
- QualType ZeroArgCallTy;
UnresolvedSet<4> Overloads;
- if (tryExprAsCall(*E.get(), ZeroArgCallTy, Overloads) &&
- !ZeroArgCallTy.isNull() &&
- (!IsPlausibleResult || IsPlausibleResult(ZeroArgCallTy))) {
- // At this point, we know E is potentially callable with 0
- // arguments and that it returns something of a reasonable type,
- // so we can emit a fixit and carry on pretending that E was
- // actually a CallExpr.
- SourceLocation ParenInsertionLoc = getLocForEndOfToken(Range.getEnd());
- bool IsMV = IsCPUDispatchCPUSpecificMultiVersion(E.get());
- Diag(Loc, PD) << /*zero-arg*/ 1 << IsMV << Range
- << (IsCallableWithAppend(E.get())
- ? FixItHint::CreateInsertion(ParenInsertionLoc, "()")
- : FixItHint());
- if (!IsMV)
- notePlausibleOverloads(*this, Loc, Overloads, IsPlausibleResult);
-
- // FIXME: Try this before emitting the fixit, and suppress diagnostics
- // while doing so.
- E = BuildCallExpr(nullptr, E.get(), Range.getEnd(), None,
- Range.getEnd().getLocWithOffset(1));
- return true;
- }
+ // If this is a SFINAE context, don't try anything that might trigger ADL
+ // prematurely.
+ if (!isSFINAEContext()) {
+ QualType ZeroArgCallTy;
+ if (tryExprAsCall(*E.get(), ZeroArgCallTy, Overloads) &&
+ !ZeroArgCallTy.isNull() &&
+ (!IsPlausibleResult || IsPlausibleResult(ZeroArgCallTy))) {
+ // At this point, we know E is potentially callable with 0
+ // arguments and that it returns something of a reasonable type,
+ // so we can emit a fixit and carry on pretending that E was
+ // actually a CallExpr.
+ SourceLocation ParenInsertionLoc = getLocForEndOfToken(Range.getEnd());
+ bool IsMV = IsCPUDispatchCPUSpecificMultiVersion(E.get());
+ Diag(Loc, PD) << /*zero-arg*/ 1 << IsMV << Range
+ << (IsCallableWithAppend(E.get())
+ ? FixItHint::CreateInsertion(ParenInsertionLoc,
+ "()")
+ : FixItHint());
+ if (!IsMV)
+ notePlausibleOverloads(*this, Loc, Overloads, IsPlausibleResult);
+
+ // FIXME: Try this before emitting the fixit, and suppress diagnostics
+ // while doing so.
+ E = BuildCallExpr(nullptr, E.get(), Range.getEnd(), None,
+ Range.getEnd().getLocWithOffset(1));
+ return true;
+ }
+ }
if (!ForceComplain) return false;
bool IsMV = IsCPUDispatchCPUSpecificMultiVersion(E.get());
diff --git a/clang/lib/Sema/SemaExprMember.cpp b/clang/lib/Sema/SemaExprMember.cpp
index f67ef030feb7..dfd93aa4638d 100644
--- a/clang/lib/Sema/SemaExprMember.cpp
+++ b/clang/lib/Sema/SemaExprMember.cpp
@@ -1645,6 +1645,9 @@ static ExprResult LookupMemberExpr(Sema &S, LookupResult &R,
<< 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,
diff --git a/clang/test/SemaTemplate/pr52970.cpp b/clang/test/SemaTemplate/pr52970.cpp
new file mode 100644
index 000000000000..7585fba41208
--- /dev/null
+++ b/clang/test/SemaTemplate/pr52970.cpp
@@ -0,0 +1,63 @@
+// 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=cxx20 %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; };
+ // cxx20-note at -1 {{because 't.a.b' would be invalid: reference to non-static member function must be called}}
+
+static_assert(C<Good>);
+static_assert(!C<Bad>);
+static_assert(C<Bad>); // cxx20-error {{static_assert failed}}
+ // cxx20-note at -1 {{because 'DotFollowingFunctionName::Bad' does not satisfy 'C'}}
+#endif
+} // namespace DotFollowingFunctionName
+
+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(); };
+ // cxx20-note at -1 {{because 't.begin()' would be invalid: member reference type 'Holder<Incomplete> *' is a pointer}}
+
+static_assert(C<Good>);
+static_assert(!C<Bad>);
+static_assert(C<Bad>); // cxx20-error {{static_assert failed}}
+ // cxx20-note at -1 {{because 'DotFollowingPointer::Bad' (aka 'Holder<Incomplete> *') does not satisfy 'C'}}
+#endif
+} // namespace DotFollowingPointer
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