own: name the overridable method a call reaches; immortal array globals; an array changed through a borrowing local (TSLANG 60-62) - #853

TSLANG_ISSUES 60, 61 and 62, found by compiling powder_sandbox's -mm=own build (native_ts_graphics as its submodule) with the compiler from main. Write-ups are in TSLANG_ISSUES.md.

60: name the overridable method a call reaches where a borrow ends

const name = this.name; for (...) this.props[i].tick(t); ... name (ntg core/rtxpt_game.ts) was refused with only "it may be released or overwritten here" at the call.

• The cause: Prop.tick calls setNodeTransform, which calls a method of the exported, non-@final GameWorld. Another module may override that method, so the call may destroy anything.
• The gap: TSLANG 48 named such a method only when the call itself was the virtual one.
• The fix: the signature pass now finds the one overridable method a call's callees reach (markOverridableReached, breadth first through calls that may destroy anything, memoized per callee). The error gets a note: "'Prop.tick' calls 'setNodeTransform', which calls 'GameWorld.setGameNodeTransform'; that method may be overridden in another module by a method that does; '@Final' on the method, or on its class, says it is not".
• When it is given: only when that method is the sole reason. No other overridable method, unknown or imported callee, or body that destroys anything is on the way, so @final on it is enough.
• What it changes: only the diagnostic; nothing new compiles. In the sweep 48 errors carry the note: MsvcRandom (41) and GameWorld (7), ntg's @finals to add.

61: an array global nothing assigns is immortal

[CUBE_VERTICES, PLANE_VERTICES, CUBE_VERTICES], return GREEN; and const p = CAMERA_POSITION; held across calls (ntg examples) were refused as borrows of a mortal global. So was a plain const A = [1.0, 2.0] read into an array literal.

• The cause: only a global of a class type could be immortal (own spec 25).
• The fix: an array global qualifies on the same terms: not exported, written once by its initializer, and given a fresh array, nothing, or another immortal global's value.
• The immortal block: the array's header, which every array release tests first. The initializing store marks it only when it is mortal, since a constant array's header is in read-only data.
• Still bounded: an element overwritten, popped or spliced out still frees the old element, so a borrow of G[i] used after that is refused.
• Still mortal: a global that is pushed to, or written in any other way through its address.
• Spec: spec 25 has the amendment.

62: an array changed through a local that borrows its field

const model = this.refractionModel; ... model.push(0.0); (ntg examples/ray_tracing_extended.ts and its NRI ports) was refused: "borrows a field and cannot be stored, returned or captured".

• The cause: push, pop, unshift, shift and splice take the slot that holds the array's header, and that was taken as the local keeping the field's value.
• The fix: the slot holds the field's array, so each such op through the local is now a use of the borrow (collectBorrowerUses).
• Still refused: an element read before a pop and used after it; the field given another array before a use; the local returned.
• A field with no array yet: a field holding a null header (never given an array) gets one in the local's slot only, which nothing frees. That is undefined in TypeScript terms, as the array spec's ruling T4-D accepts for a parameter.

Effect on the sweep (276 sources, every facts object built)

• Sources failing: 126 → 119. Now compiling: ptlas.ts, ray_tracing_reflection.ts, collision.ts, nvrhi_direct.ts, async_compute_bloom.ts, msaa.ts, texture_compression_comparison.ts.
• Errors: 907 → 807.
• ray_tracing_reflection_nri.ts: 29 errors → 1.

Tests

• New tests: 00tslang_issue_60.ts, 00tslang_issue_61.ts and 00tslang_issue_62.ts, under every model, JIT and compiled.
• New own error tests: own_err_overridable_reached, own_err_immortal_array_element_overwritten and own_err_borrowed_array_pushed_returned.
• ctest (Windows Release): 7284/7284.
• DefaultLib main (6806d40) rebuilt with this compiler, release and debug, all four models. tests.ps1 for each model is running; results to follow in a comment.

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