Document remaining const_cast sites as upward mailboxes; add A7 channel proposal#212
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…el proposal The 10 remaining const_cast<GenContext&> casts all intentionally write into the caller''s context so later code observes the value (field-init statement queue, safe-cast aliases, this-parameter type, dispose marker, switch-state arming). Copy-on-override cannot work for these and GenContext& would ripple through the whole statement chain; their correctness depends on value-copy visibility, which A7 in the review doc now explains, with a per-channel redesign proposal. Each site carries a greppable "NOTE: upward mailbox" comment. No code behavior change (comments and docs only). Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Summary
Closes the mechanical portion of the A6
const_cast<GenContext&>effort and documents what's left. Comments and docs only — no behavior change.Investigating the final 10 casts (8 in MLIRGen.cpp, 2 in
MLIRCodeLogic.h) showed they are all upward mailboxes: they intentionally write into the caller's context so later code observes the value — the class-field-init statement queue (generatedStatementspush/drain), synthesized safe-cast aliases (typeAliasMap), the explicitthis: Tparameter type (mlirGenParameters), the dispose process-once marker (usingVars), and__switchstatearming variable-allocation placement for following statements. Copy-on-override cannot work for these,GenContext&signatures would ripple through the entire statement chain, and — the key finding — their correctness depends onGenContext's value-copy visibility semantics (a write is visible exactly to contexts copied from the mutated object after the write). The original phase-4 guess ("plain parameters") was wrong: those are out-channels too.NOTE: upward mailboxcomment pointing at the doc.docs/MLIRGen-refactoring-review.mdexplains the mechanism and proposes a per-channel redesign (pointer-shared channel object for the statement queue, per-function registry for safe-cast aliases, returned values instead of pokes formlirGenParameters/mlirGenSwitchState), one PR per channel, each needing review before implementation.Series scorecard for §3: 31 casts → 10, with every eliminated cast either provably semantics-free or a fixed latent leak, and every survivor documented.
Test plan
tslangrebuilds cleanly; smoke subset +MLIRGenTests.exe12/12 (comment-only change)🤖 Generated with Claude Code