Fix shared substitution slices and open-variable capture - #229
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RSoulatIOHK wants to merge 1 commit into
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Fix shared substitution slices and open-variable capture#229RSoulatIOHK wants to merge 1 commit into
RSoulatIOHK wants to merge 1 commit into
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Shared substitution disagrees with Lean's native implementation when the argument slice begins after zero, and it captures open replacement variables under binders. For example, substituting slice
[1, 2)of[10, 20]intobvar 0returnsbvar 0instead of20.Use the slice offset only when indexing the replacement array, lift open replacements by the binder depth, and pass the requested slice through shared beta reduction. Closed arguments keep their existing fast path; empty slices return immediately.
Fixes #227.
Tests/FixedIssues/Issue227.leancompares 3,600 substitution cases and 40 beta cases with Lean's native implementation, and includes two optimizer regressions and a Blaster call.lake build Tests.FixedIssues.Issue227passes.This is a helper correctness fix; the reported cases have not been shown to produce a false top-level Blaster theorem. Stacked on #224.