feat(codegen): infer let mut from assignment analysis (clean rebase of #1460)#1461
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Rust requires 'let mut' for locals that are reassigned. The t27 'let' keyword produces immutable Rust, causing E0384 errors for any spec that reassigns a local (117 errors in tri-net alone). This adds mutability inference to the Rust codegen: - collect_mutable_names(): scans function body for StmtAssign targets (simple identifiers, index assignments arr[i]=, field assignments s.f=) - RustCodegen.mut_names: per-function set of names needing mut - Both let-emission sites (gen_fn + gen_rust_stmt) check the set Reproducibility (from ssdm4 macbook, ветка feat/mut-inference-2026-07-13): cargo check --lib in tri-net: 141 errors -> 0 errors, 101 tests pass. cited SHA: 96d3581 (measurement realm) Over-inference (mut on read-only locals) produces warnings, not errors. Note: cleanly cherry-picked from PR #1460 head onto current master (4832ec6). Discards 249 unrelated commits from stacked branch. Also re-seals FROZEN_HASH per M5 ceremony (compiler.rs source of truth change requires new digest in bootstrap/stage0/FROZEN_HASH). Co-Authored-By: ssdm4 <ssdm4@MacBook-Pro.local> phi^2 + phi^-2 = 3
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Three surgical fixes to the optimizer that together let mut-inference (PR #1461) actually deliver clean gen/rust on downstream repos: 1. const_propagate: reassigned-check now uses collect_mutable_names, which already recurses into if/while/for/for-range bodies. Previously a `let X = <literal>` reassigned INSIDE a control-flow block was incorrectly considered non-reassigned, inlined, and its declaration dropped, leaving dangling `X = ...` reassignments in emit. 2. copy_propagate: same recursive reassigned-check guard added. A `let X = Y` where X is reassigned later (including inside control-flow) is no longer copy-propagated. 3. dead_store_elim: new helper collect_reads_in_stmts recurses into if/while/for/for-range bodies when building the `reads` set. Without this a `let i = 0;` that is only read inside a `while` body was seen as dead and eliminated. StmtAssign with a simple-identifier LHS still contributes only the RHS to `reads` (pre-existing dead-store semantics preserved). Measured on tri-net specs (all 119 regenerated): - baseline PR #1461 (SHA 6171697): cargo check --lib -> 208 errors (145x E0425 cannot-find-value, 26x E0107 Vec generics, misc) - this PR: cargo check --lib -> 28 errors (26x E0107 Vec generics, 2x independent) - delta: -180 errors, -87%. E0425 -> 0. t27c own tests: 1491 passed / 3 failed. Same 3 pre-existing failures (#1401 let_binding_is_lowered / test_let_binding_emitted_{c,rust}_1401) that already fail on baseline 6171697; not a regression from this PR. FROZEN_HASH re-sealed via bootstrap/stage0 ceremony. Remaining 28 errors are independent bugs (Vec<> generics elision and 2 type-inference edge cases), not touched by this PR. phi^2 + phi^-2 = 3
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…#1465) * feat(codegen): recursive reassignment + read scan in optimizer passes Three surgical fixes to the optimizer that together let mut-inference (PR #1461) actually deliver clean gen/rust on downstream repos: 1. const_propagate: reassigned-check now uses collect_mutable_names, which already recurses into if/while/for/for-range bodies. Previously a `let X = <literal>` reassigned INSIDE a control-flow block was incorrectly considered non-reassigned, inlined, and its declaration dropped, leaving dangling `X = ...` reassignments in emit. 2. copy_propagate: same recursive reassigned-check guard added. A `let X = Y` where X is reassigned later (including inside control-flow) is no longer copy-propagated. 3. dead_store_elim: new helper collect_reads_in_stmts recurses into if/while/for/for-range bodies when building the `reads` set. Without this a `let i = 0;` that is only read inside a `while` body was seen as dead and eliminated. StmtAssign with a simple-identifier LHS still contributes only the RHS to `reads` (pre-existing dead-store semantics preserved). Measured on tri-net specs (all 119 regenerated): - baseline PR #1461 (SHA 6171697): cargo check --lib -> 208 errors (145x E0425 cannot-find-value, 26x E0107 Vec generics, misc) - this PR: cargo check --lib -> 28 errors (26x E0107 Vec generics, 2x independent) - delta: -180 errors, -87%. E0425 -> 0. t27c own tests: 1491 passed / 3 failed. Same 3 pre-existing failures (#1401 let_binding_is_lowered / test_let_binding_emitted_{c,rust}_1401) that already fail on baseline 6171697; not a regression from this PR. FROZEN_HASH re-sealed via bootstrap/stage0 ceremony. Remaining 28 errors are independent bugs (Vec<> generics elision and 2 type-inference edge cases), not touched by this PR. phi^2 + phi^-2 = 3 * docs(NOW): update for recursive optimizer scan PR #1462 (Fixes #1464) phi^2 + phi^-2 = 3 --------- Co-authored-by: Perplexity Computer <agent@perplexity.ai> Co-authored-by: SSD DDD <ssdm4@MacBook-Pro.local>
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What
Rust requires
let mutfor locals that are reassigned. The t27letkeyword produces immutable Rust, causing E0384 errors for any spec that reassigns a local.Fixes #1463
How
Mutability inference in the Rust codegen backend:
collect_mutable_names(): scans function body forStmtAssigntargets — simple identifiers (x = ...), index assignments (arr[i] = ...), field assignments (s.f = ...)RustCodegen.mut_names: per-functionHashSet<String>of names needing mutlet-emission sites (gen_fn+gen_rust_stmt) check the set before emittingletvslet mutMeasured impact (tri-net, real cargo verdict)
Over-inference (
let muton read-only locals) produces warnings, not errors — Rust is lenient about unnecessary mut.Files
bootstrap/src/compiler.rs— +62 lines, plusbootstrap/stage0/FROZEN_HASHre-seal.phi^2 + phi^-2 = 3