Please consider the below example
struct Test{
Test(int){}
};
int main(){
int a = 0;
int b = 0;
bool c = true;
Test t = c?a:b = 1;
}
All compilers agree that this statement Test t = c?a:b = 1; is well-formed. However I have doubt for this result.
First, for this text Test t = c?a:b = 1;, it's a declaration, which has an initializer, such an initializer has the form:
brace-or-equal-initializer:
= initializer-clause
initializer-clause is either
assignment-expression or
braced-init-list
In my example, the initializer-clause should be assignment-expression which is denoted by text c?a:b = 1, and an valid assignment-expression shall satisfy one of these grammars:
assignment-expression
- conditional-expression
- logical-or-expression assignment-operator initializer-clause
- throw-expression
For this text c?a:b = 1, the assignment-operator is = and the initializer-clause is 1 which is literal(one kind of primary-expression, i.e, an valid initializer-clause).
What I can't understand is here, the left part of = shall be an logical-or-expression. However in my example, the left part is c?a:b which is a conditional expression. In other words, I can't find any valid form in grammar tree of logical-or-expression which can denote c?a:b. Namely, conditional-expression is not subsumed into logical-or-expression.
That means, this assignment-expression c?a:b = 1 should have be ill-formed. But all compilers say that it's well-formed, how to interpret this? why the text c?a:b = 1 can be as a valid assignment-expression?
