add note about VRP not applying to assignment operator exps#23101
add note about VRP not applying to assignment operator exps#23101WalterBright wants to merge 1 commit into
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What does that mean? |
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I'm not sure, but it looks like your parentheses are unbalanced here. |
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It's opening a double link |
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@dkorpel thanks! |
| the binary operators. Still the left operand must be an lvalue. | ||
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| $(P $(DDSUBLINK spec/type.html, vrp, Value Range Propagation) does not apply to assignment operator expressions:) |
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VRP is part of implicit conversions. For built-in types, a op= b is defined as doing a cast / explicit conversion, so VRP isn't even a possibility. And for custom types, where an implicit conversion happens to the argument type, VRP does apply:
struct S
{
auto opOpAssign(string op)(ubyte value)
{
return this;
}
}
void f(S b, uint i)
{
b *= i; // Error
b *= i & 0xFF; // No error
}So the statement is either irrelevant or incorrect, it's best left out.
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The spec for a op= b can certainly be adapted to do VRP. As for opOpAssign, it is up to the user implementation of it to use VRP or not.
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it is up to the user implementation of it to use VRP or not.
Then the PR should demonstrate that instead of stating something false.
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For reference: #19075 (comment)