Fixes #24914 Treat equivalent candidates as divergent in implicit search#25910
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Fixes #24914 Treat equivalent candidates as divergent in implicit search#25910soronpo wants to merge 2 commits intoscala:mainfrom
soronpo wants to merge 2 commits intoscala:mainfrom
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The divergence check in `checkDivergence` only considered two open searches as potential loops when they used the exact same candidate reference. Given several sibling givens with identical declared types — a common pattern when modelling a type class hierarchy where each instance recursively needs another instance — the search would still branch into every permutation of the candidates before eventually giving up once the expression-count limit tripped. For the minimization in scala#24914 this was a factorial blow-up: six sibling Monad givens led to tens of thousands of `tryImplicit` calls and compilation took well over a minute before failing with "search problem too large". Extending the check so that candidates whose `ref.info` types are equivalent are also subject to the usual size and covering-set test lets ordinary divergence detection cut the recursion short; the test file now fails in roughly five seconds with a clean error instead. https://claude.ai/code/session_01JTYTJU8w2jxH1QLqD8of4x
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The divergence check in
checkDivergenceonly considered two open searches as potential loops when they used the exact same candidate reference. Given several sibling givens with identical declared types — a common pattern when modelling a type class hierarchy where each instance recursively needs another instance — the search would still branch into every permutation of the candidates before eventually giving up once the expression-count limit tripped.For the minimization in #24914 this was a factorial blow-up: six sibling Monad givens led to tens of thousands of
tryImplicitcalls and compilation took well over a minute before failing with "search problem too large". Extending the check so that candidates whoseref.infotypes are equivalent are also subject to the usual size and covering-set test lets ordinary divergence detection cut the recursion short; the test file now fails in roughly five seconds with a clean error instead.Fixes #24914
How much have you relied on LLM-based tools in this contribution?
Extensively, but the fix is small.
How was the solution tested?
New automated tests (including the issue's reproducer, if applicable)