Bug 19038 – Cannot compare const(T)[][] and T[][]

This code works: [cast(const) "a"] == ["a"]; This code doesn't work. [[cast(const) "a"]] == [["a"]];

From a quick glance at the source, DMD might be rejecting comparisons of arrays that don't have a common type [1][2]. And apparently, it thinks that `Foo[][]` and `const(Foo)[][]` don't have a common type. But that's wrong. `const(Foo[])[]` is one. Another symptom of that possible root cause: ---- void main() { int[][] a1; const(int)[][] a2; const(int[])[] common; common = true ? a1 : a2; /* "Error: incompatible types" */ /* But: */ if (true) common = a1; else common = a2; /* correctly accepted */ /* So there is a common type. The ternary expression should be accepted. */ } ---- [1] https://github.com/dlang/dmd/blob/033d324957ff5bee8e25c7335eab2c562d17e2b1/src/dmd/expressionsem.d#L9059-L9066 [2] https://github.com/dlang/dmd/blob/033d324957ff5bee8e25c7335eab2c562d17e2b1/src/dmd/dcast.d#L3339-L3344

Just casting both sides to const seems to work. https://github.com/dlang/dmd/pull/8413

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