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Chandler Carruth
d010d52f37
As part of this, move functions that seem reasonable to make out-of-line to a separate `_impl.h` header file that is only included where the explicit instantiation _definition_ is provided. By using explicit instantiation we can make these templates behave more like non-template classes in terms of supporting out-of-line definitions that don't need to be compiled by every translation unit. The set of eventual instantiations here is fundamentally known, and there tend to be headers that define a canonical "leaf" type where it makes sense to trigger the explicit instantiation. Where we already had a `.cpp` file to put the explicit instantiation definition, use it. But in some places we didn't have such a `.cpp` file so this PR adds those. This also requires that we have precise constraints on APIs that _can't_ be instantiated for specific argument types, as now we don't do this lazily. Combined, this appears to reduce the sum of object file sizes in the `check` directory by almost 40% (122mb -> 74mb) in my measurement. My actual goal was to improve compile times, but so far I don't have a great methodology for measuring these... But the object file size reduction seems to confirm this is a net win and likely represents a non-trivial improvement in compile time. Assisted-by: Antigravity with Gemini