Add nullness regression test for recursive inline SRTP memoization - #20247
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The function-domain unification order change in PR #15181 (nullness) caused recursive inline SRTP resolution to be truncated by one currying level: an inference variable still carrying an unsolved member constraint could be absorbed by the required domain, merging away the pending recursive trait resolution. This regressed patterns such as FSharpPlus `memoizeN`. SolveFunTypeEqn now keeps the SRTP-constrained inference variable as the unification representative for that specific case, and only when not MatchingOnly (mirroring SolveTypeEqualsType). Adds two ComponentTests (the memoizeN repro across currying depths, and a MatchingOnly overload-resolution guard) and repoints the FSharpPlus regression matrix at a minimal global.json-bump branch that exercises the fix end-to-end. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 4cfb1c86-0d7e-45e6-9529-3c5f301c0912
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Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 4cfb1c86-0d7e-45e6-9529-3c5f301c0912
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Trim the SolveFunTypeEqn comment to the why + bug link + MatchingOnly invariant, drop the depth-2 memoization control block (depth-3 is the minimal reproducing case), and count invocations with a mutable int instead of a ResizeArray of unused labels. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 4cfb1c86-0d7e-45e6-9529-3c5f301c0912
Locks that the domain-order fix in SolveFunTypeEqn keeps recursive inline SRTP memoization nullness-neutral under --checknulls+: a nullable argument annotation still flows through the recursive specialization and produces the same precise FS3261 deref warning (no lost/spurious warning, no internal error). Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 4cfb1c86-0d7e-45e6-9529-3c5f301c0912
…tp-regression # Conflicts: # azure-pipelines-PR.yml
…tp-regression # Conflicts: # src/Compiler/Checking/ConstraintSolver.fs # tests/FSharp.Compiler.ComponentTests/Conformance/Types/TypeConstraints/IWSAMsAndSRTPs/IWSAMsAndSRTPsTests.fs
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The recursive inline SRTP resolution fix (FSharpPlus
memoizeN) landed in #19785. This adds the one piece that PR didn't carry: a--checknulls+regression test locking that the domain-order fix stays nullness-neutral — a nullable argument annotation still flows through the recursive specialization and produces the same preciseFS3261dereference warning, with no lost or spurious warning and no internal error.