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[Concepts] Implement P1616R1 - Using unconstrained template template parameters with constrained templates 

Summary: Allow unconstrained template template parameters to accept constrainted templates as arguments.

Reviewers: rsmith

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D73155
This commit is contained in:
Saar Raz 2020-01-22 04:21:09 +02:00
parent c77bbea9a6
commit d42d5eb8ea
2 changed files with 10 additions and 5 deletions
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5
clang/lib/Sema/SemaTemplate.cpp
View File

@ -7164,6 +7164,11 @@ bool Sema::CheckTemplateTemplateArgument(TemplateTemplateParmDecl *Param,
// [temp.constr.order]. // [temp.constr.order].
SmallVector<const Expr *, 3> ParamsAC, TemplateAC; SmallVector<const Expr *, 3> ParamsAC, TemplateAC;
Params->getAssociatedConstraints(ParamsAC); Params->getAssociatedConstraints(ParamsAC);
// C++2a[temp.arg.template]p3
// [...] In this comparison, if P is unconstrained, the constraints on A
// are not considered.
if (ParamsAC.empty())
return false;
Template->getAssociatedConstraints(TemplateAC); Template->getAssociatedConstraints(TemplateAC);
bool IsParamAtLeastAsConstrained; bool IsParamAtLeastAsConstrained;
if (IsAtLeastAsConstrained(Param, ParamsAC, Template, TemplateAC, if (IsAtLeastAsConstrained(Param, ParamsAC, Template, TemplateAC,

10
clang/test/CXX/temp/temp.arg/temp.arg.template/p3-2a.cpp
View File

@ -7,9 +7,9 @@ template<typename T> concept F = T::f();
// expected-note@-1{{similar constraint expressions not considered equivalent}} // expected-note@-1{{similar constraint expressions not considered equivalent}}
template<template<C> class P> struct S1 { }; // expected-note 2{{'P' declared here}} template<template<C> class P> struct S1 { }; // expected-note 2{{'P' declared here}}
template<C> struct X { }; // expected-note{{'X' declared here}} template<C> struct X { };
template<D> struct Y { }; // expected-note 2{{'Y' declared here}} template<D> struct Y { }; // expected-note{{'Y' declared here}}
template<typename T> struct Z { }; template<typename T> struct Z { };
template<F> struct W { }; // expected-note{{'W' declared here}} template<F> struct W { }; // expected-note{{'W' declared here}}
@ -18,10 +18,10 @@ S1<Y> s12; // expected-error{{template template argument 'Y' is more constrained
S1<Z> s13; S1<Z> s13;
S1<W> s14; // expected-error{{template template argument 'W' is more constrained than template template parameter 'P'}} S1<W> s14; // expected-error{{template template argument 'W' is more constrained than template template parameter 'P'}}
template<template<typename> class P> struct S2 { }; // expected-note 2{{'P' declared here}} template<template<typename> class P> struct S2 { };
S2<X> s21; // expected-error{{template template argument 'X' is more constrained than template template parameter 'P'}} S2<X> s21;
S2<Y> s22; // expected-error{{template template argument 'Y' is more constrained than template template parameter 'P'}} S2<Y> s22;
S2<Z> s23; S2<Z> s23;
template <template <typename...> class C> template <template <typename...> class C>