Fix #6909: Use memo to cache given aliases #6939
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dottybot
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Jul 26, 2019
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Implement `memo(...)` function which caches its argument on first evaluation and re-uses the cached value afterwards. The cache is placed next to the method enclosing the memo(...) call. `memo` is a member of package `compiletime`.
Maybe we should always set the positions of these generated definitions automatically from the symbol's span. It's an easy trap to fall into.
Stale symbol errors can happen when inspecting symbols while comparing the trees before and after pickling.
... and also make it work on several nested levels together.
Restricting `entered` and `enteredAfter` to class members is more a trap to fall into than a helpful check.
The new implementation does not optimize given aliases with pure paths as right hand sides to be vals anymore. The reason is that even a pure path might be expensive to compute so we might want the caching. And caching is cheap, so there's little downside. Therefore, it's attractive to go with the simpler two way choice: leave RHS as is, or wrap it in a memo.
An inline given instance with a splice as right hand side should not be cached.
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Superseded by #6967 |
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See 2ab9140 for docs.