decomposed-condition.cpp
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// RUN: %clang_cc1 -std=c++1z -Wno-binding-in-condition -verify %s
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)
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)
return a;
else
return b;
if (auto [a, b] = x) // expected-error {{an array type is not allowed here}}
;
}
static_assert(g("x") == 'x');
} // namespace CondInIf
namespace CondInSwitch {
constexpr int f(int n) {
switch (X s = {true, n}; auto [ok, d] = s) {
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}) {
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) {
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