mirror of
https://github.com/llvm/llvm-project.git
synced 2025-04-17 17:46:49 +00:00
f4218753ad
This implements the R2 semantics of P0963. The R1 semantics, as outlined in the paper, were introduced in Clang 6. In addition to that, the paper proposes swapping the evaluation order of condition expressions and the initialization of binding declarations (i.e. std::tuple-like decompositions).
107 lines
3.0 KiB
C++
107 lines
3.0 KiB
C++
// RUN: %clang_cc1 -std=c++17 -Wno-c++26-extensions -verify %s
|
|
// RUN: %clang_cc1 -std=c++17 -Wno-c++26-extensions -verify %s -fexperimental-new-constant-interpreter
|
|
// RUN: %clang_cc1 -std=c++2c -Wpre-c++26-compat -verify=cxx26,expected %s
|
|
// RUN: %clang_cc1 -std=c++2c -Wpre-c++26-compat -verify=cxx26,expected %s -fexperimental-new-constant-interpreter
|
|
|
|
struct X {
|
|
bool flag;
|
|
int data;
|
|
constexpr explicit operator bool() const {
|
|
return flag;
|
|
}
|
|
constexpr operator int() const {
|
|
return data;
|
|
}
|
|
};
|
|
|
|
namespace CondInIf {
|
|
constexpr int f(X x) {
|
|
if (auto [ok, d] = x) // cxx26-warning {{structured binding declaration in a condition is incompatible with C++ standards before C++2c}}
|
|
return d + int(ok);
|
|
else
|
|
return d * int(ok);
|
|
ok = {}; // expected-error {{use of undeclared identifier 'ok'}}
|
|
d = {}; // expected-error {{use of undeclared identifier 'd'}}
|
|
}
|
|
|
|
static_assert(f({true, 2}) == 3);
|
|
static_assert(f({false, 2}) == 0);
|
|
|
|
constexpr char g(char const (&x)[2]) {
|
|
if (auto &[a, b] = x) // cxx26-warning {{structured binding declaration in a condition is incompatible with C++ standards before C++2c}}
|
|
return a;
|
|
else
|
|
return b;
|
|
|
|
if (auto [a, b] = x) // expected-error {{an array type is not allowed here}} \
|
|
// cxx26-warning {{structured binding declaration in a condition is incompatible with C++ standards before C++2c}}
|
|
;
|
|
}
|
|
|
|
static_assert(g("x") == 'x');
|
|
} // namespace CondInIf
|
|
|
|
namespace CondInSwitch {
|
|
constexpr int f(int n) {
|
|
switch (X s = {true, n}; auto [ok, d] = s) {
|
|
// cxx26-warning@-1 {{structured binding declaration in a condition is incompatible with C++ standards before C++2c}}
|
|
s = {};
|
|
case 0:
|
|
return int(ok);
|
|
case 1:
|
|
return d * 10;
|
|
case 2:
|
|
return d * 40;
|
|
default:
|
|
return 0;
|
|
}
|
|
ok = {}; // expected-error {{use of undeclared identifier 'ok'}}
|
|
d = {}; // expected-error {{use of undeclared identifier 'd'}}
|
|
s = {}; // expected-error {{use of undeclared identifier 's'}}
|
|
}
|
|
|
|
static_assert(f(0) == 1);
|
|
static_assert(f(1) == 10);
|
|
static_assert(f(2) == 80);
|
|
} // namespace CondInSwitch
|
|
|
|
namespace CondInWhile {
|
|
constexpr int f(int n) {
|
|
int m = 1;
|
|
while (auto [ok, d] = X{n > 1, n}) {
|
|
// cxx26-warning@-1 {{structured binding declaration in a condition is incompatible with C++ standards before C++2c}}
|
|
m *= d;
|
|
--n;
|
|
}
|
|
return m;
|
|
return ok; // expected-error {{use of undeclared identifier 'ok'}}
|
|
}
|
|
|
|
static_assert(f(0) == 1);
|
|
static_assert(f(1) == 1);
|
|
static_assert(f(4) == 24);
|
|
} // namespace CondInWhile
|
|
|
|
namespace CondInFor {
|
|
constexpr int f(int n) {
|
|
int a = 1, b = 1;
|
|
for (X x = {true, n}; auto &[ok, d] = x; --d) {
|
|
// cxx26-warning@-1 {{structured binding declaration in a condition is incompatible with C++ standards before C++2c}}
|
|
if (d < 2)
|
|
ok = false;
|
|
else {
|
|
int x = b;
|
|
b += a;
|
|
a = x;
|
|
}
|
|
}
|
|
return b;
|
|
return d; // expected-error {{use of undeclared identifier 'd'}}
|
|
}
|
|
|
|
static_assert(f(0) == 1);
|
|
static_assert(f(1) == 1);
|
|
static_assert(f(2) == 2);
|
|
static_assert(f(5) == 8);
|
|
} // namespace CondInFor
|