Constness and immutability of AA keys is handled unflexibly

[0xEAB]

/opt/ldc2-1.42.0/bin/../import/core/internal/newaa.d(172): Error: cannot implicitly convert expression `key` of type `const(char[])` to `string`
        entry.key = key;

But if key were const(char)[] it would happily work.

int[string] properties;

auto keyName = key.data; // `const(char)[]`
properties[keyName] = value; // works

const keyName = key.data; // compiler eats the other `const` and simplifies this to `const(char[])`
properties[keyName] = value; // doesn't work

[rainers]

A full example is recommended to avoid misunderstandings. This code

void test(int[string] properties)
{
    const(char)[] keyName = "1";
    properties[keyName] = 1;

    const keyName2 = keyName;
    properties[keyName2] = 2;
}

compiles up until dmd 2.111, but I think it is invalid, as a const(char)[] is not convertible to string (as now reported) when storing the key as part of the assignment. Reading properties with the given types works.

There are a couple of old bug reports discussing what type the key of an AA should have (implicitly immutable, const or mutable as declared), but I don't remember anyone asking for this conversion.

Edit: not sure yet why the first assignment is accepted, though. Assigning keyName to a string fails.

[rainers]

Edit: not sure yet why the first assignment is accepted, though. Assigning keyName to a string fails.

There is a workaround to allow the first conversion for backward compatibilty but that did not include const(char[]). See #23321