Bug 19071 – core.internal.hash should have non-chained toHash overloads

Each hash function in `core.internal.hash` currently has the form: ``` size_t hashOf(T)(auto ref T val, size_t seed = 0); ``` The idea behind the second `seed` argument was to allow "chaining", e.g. `hashOf(z, hashOf(x, hashOf(y)))`. The downside is that for any type for which `hashOf` is not a wrapper around `bytesHash` this performs additional work which can be avoided if chaining is not needed. To fix this instead of a single function with a default argument there should be two overloads: ``` size_t hashOf(T)(auto ref T val, size_t seed); size_t hashOf(T)(auto ref T val); ``` Aside from avoiding unnecessary work for cases like `hashOf(uint(x))`, this would also cause `hashOf(y)` to be the same as `y.toHash`: ``` unittest { static struct Record { size_t id; int[string] properties; size_t toHash() const @nogc nothrow pure @safe { return id; } } Record record = { id: 3 }; assert(record.toHash() == hashOf(record)); // Currently fails! } ```

Commits pushed to master at https://github.com/dlang/druntime https://github.com/dlang/druntime/commit/2f1275cee4fc865ae32c14be43a3a106c425eb92 Fix Issue 19071 - core.internal.hash should have non-chained toHash overloads https://github.com/dlang/druntime/commit/711ab1c68094458c1ba0a6ea7a214c35157391a2 Merge pull request #2246 from n8sh/core-hash-19071 Fix Issue 19071 - core.internal.hash should have non-chained toHash overloads merged-on-behalf-of: Sebastian Wilzbach <[email protected]>