Fix generic constraint matching for method-shaped receivers#273
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ASDAlexander77 merged 1 commit intoJul 21, 2026
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…am misalignment)
extendsTypeFuncTypes skipped the receiver's bound `this` param when
comparing against a method-shaped constraint (e.g. `T extends { next(): ... }`),
but never skipped the constraint's own leading `this` placeholder (OpaqueType)
in lockstep. That misaligned the two param lists by one, so every extension
method whose generic constraint required a method field (e.g. DefaultLib's
__Iterator.take/drop/every/filter/find/forEach/map/reduce/some/toArray on
generator return types) failed to resolve.
Also add ObjectType/ObjectStorageType cases to getFieldTypeByFieldName so
boxed generator return types expose their fields to structural constraint
checks.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
ASDAlexander77
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fix/iterator-helper-extension-constraint-mismatch
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July 21, 2026 17:47
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Summary
extendsTypeFuncTypesskipped the receiver's boundthisparam when comparing against a method-shaped generic constraint (e.g.TIter extends { next(): {...} }), but never skipped the constraint's own leadingthisplaceholder (OpaqueType) in lockstep — misaligning the two parameter lists by one and causing every subsequent parameter comparison to fail (collapsing to<<NULL TYPE>>vs!ts.opaque).__Iterator.take/drop/every/filter/find/forEach/map/reduce/some/toArraynever resolved on generator (function*) return types (fibonacci().take(5),fibonacci().every(fn), etc. all failed to compile).ObjectType/ObjectStorageTypecases togetFieldTypeByFieldNameso a boxed generator return type exposes its fields (e.g.next()) to structural constraint checks in the first place.Root-caused via LLVM debug tracing (
-debug-only=mlir) on a Debug JIT build, isolating the exactextendsTyperecursion where the receiver'snext()method type was compared against the constraint'snext()signature and one side's parameter came back null.Test plan
tslang(Debug + Release) with the fixtests.ps1suite (release/debug × compile/jit, 150 tests × 4 = 600 runs): 150/150 passing on all four, including the 10 previously-failingiterator_*.tstests (iterator_drop/every/filter/find/forEach/map/reduce/some/take/toArray)🤖 Generated with Claude Code