diff options
Diffstat (limited to 'skills/chapter25-codex-notes.md')
| -rw-r--r-- | skills/chapter25-codex-notes.md | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/skills/chapter25-codex-notes.md b/skills/chapter25-codex-notes.md index 64738421..1aac07a2 100644 --- a/skills/chapter25-codex-notes.md +++ b/skills/chapter25-codex-notes.md @@ -367,6 +367,18 @@ Consequences: ## Types and monotonicity +- Integer widening starts in Chapter 24. `nonZero()` preserves `_widen` when + narrowing a range. B10's correction is in 24, with `TypeTest.testNonZeroWidening` + in 24-25. Both now use widening 0-3 and dual widening `3-widen`, preserve + singleton widening, and give TypeConAry the same widening coordinate. Loop Phis + widen only below-center nonconstant ranges: above-center widening can fall to + an unwidened constant, violating SCCP monotonicity. Existing Chapter14/21 tests + exposed this during the backport. +- TypeConAry's `_make(any,widen)` shares the backing array and returns an + uninterned type. `xdual()` must leave interning to Type.intern's dual-pair setup; + ordinary factories and ymeet's widening replacement intern their results. + Chapters 24-25 use this API and a distinct array tag. Chapters 22-23 only receive + compatible cleanup; their sentinel-based representations predate widening. - Cyclic structural equality starts in Chapter 23. Chapters 9-22 compare interned children by identity and check type kinds in `Type.equals`. In recursive equality, leaf dispatch must also check `_type` before calling |