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Allow sizeof(UnrelatedClass::field) in C++11 class template methods 

This feature works outside of templates by forming a DeclRefExpr to a
FieldDecl instead of a MemberExpr, which requires a base object in
addition to the FieldDecl.

Previously, while building up the template AST before instantiation, we
formed a CXXDependentScopeMemberExpr, which always instantiates to a
MemberExpr. Now, in unevaluated contexts we form a
DependentScopeDeclRefExpr, which is a more flexible node that can
instantiate to either a MemberExpr or a DeclRefExpr depending on lookup
results.

Fixes PR26893.

llvm-svn: 263279
This commit is contained in:
Reid Kleckner 2016-03-11 18:59:12 +00:00
parent e5a9a275d3
commit 1af391df13
2 changed files with 42 additions and 4 deletions
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19
clang/lib/Sema/SemaTemplate.cpp
View File

@ -414,9 +414,22 @@ Sema::ActOnDependentIdExpression(const CXXScopeSpec &SS,
const TemplateArgumentListInfo *TemplateArgs) {
DeclContext *DC = getFunctionLevelDeclContext();
if (!isAddressOfOperand &&
isa<CXXMethodDecl>(DC) &&
cast<CXXMethodDecl>(DC)->isInstance()) {
// C++11 [expr.prim.general]p12:
// An id-expression that denotes a non-static data member or non-static
// member function of a class can only be used:
// (...)
// - if that id-expression denotes a non-static data member and it
// appears in an unevaluated operand.
//
// If this might be the case, form a DependentScopeDeclRefExpr instead of a
// CXXDependentScopeMemberExpr. The former can instantiate to either
// DeclRefExpr or MemberExpr depending on lookup results, while the latter is
// always a MemberExpr.
bool MightBeCxx11UnevalField =
getLangOpts().CPlusPlus11 && isUnevaluatedContext();
if (!MightBeCxx11UnevalField && !isAddressOfOperand &&
isa<CXXMethodDecl>(DC) && cast<CXXMethodDecl>(DC)->isInstance()) {
QualType ThisType = cast<CXXMethodDecl>(DC)->getThisType(Context);
// Since the 'this' expression is synthesized, we don't need to

27
clang/test/SemaTemplate/instantiate-sizeof.cpp
View File

@ -1,5 +1,4 @@
// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 %s
// expected-no-diagnostics
// Make sure we handle contexts correctly with sizeof
template<typename T> void f(T n) {
@ -9,3 +8,29 @@ template<typename T> void f(T n) {
int main() {
f<int>(1);
}
// Make sure we handle references to non-static data members in unevaluated
// contexts in class template methods correctly. Previously we assumed these
// would be valid MemberRefExprs, but they have no 'this' so we need to form a
// DeclRefExpr to the FieldDecl instead.
// PR26893
template <class T>
struct M {
M() {}; // expected-note {{in instantiation of default member initializer 'M<S>::m' requested here}}
int m = *T::x; // expected-error {{invalid use of non-static data member 'x'}}
void f() {
// These are valid.
static_assert(sizeof(T::x) == 8, "ptr");
static_assert(sizeof(*T::x) == 4, "int");
}
};
struct S { int *x; };
template struct M<S>; // expected-note {{in instantiation of member function 'M<S>::M' requested here}}
// Similar test case for PR26893.
template <typename T=void>
struct bar {
struct foo { int array[10]; };
int baz() { return sizeof(foo::array); }
};
template struct bar<>;