ast,daslib: fix spurious 30151 on concept_assert under lint flags (#2830)

[borisbat]

Closes #2830.

Two independent bugs the lint pipeline surfaced together

The linter runs with cop.no_infer_time_folding = true + cop.no_optimizations = true. Bisect (toggle each lint policy off in turn) localizes no_infer_time_folding as the sole trigger. With infer-time folding off, two distinct paths in the codebase that quietly relied on it now break:

1. Compiler: concept_assert / static_assert cond never folds

typeinfo sizeof(T) <= typeinfo sizeof(U) rewrites itself to ExprConstInt <= ExprConstInt at infer time, but InferTypes::visit(ExprOp1/Op2/Op3) (ast_infer_type_op.cpp:106, :365, :405) only folds when enableInferTimeFolding is on. With lint disabling it and no_optimizations skipping ConstFolding, the binop stays unfolded; ContractFolding::visit(ExprStaticAssert*) (ast_const_folding.cpp:848-852) demands cond->constexpression || cond->rtti_isConstant() and raises the spurious 30151.

Fix mirrors the existing static_if save+force-enable+restore pattern (ast_infer_type.cpp:4418-4422, :4428-4430) inside preVisit(ExprStaticAssert*) / visit(ExprStaticAssert*), so the cond subtree always folds regardless of the surrounding policy.

2. Daslib: 6 sites if (typeinfo X) instead of static_if

These relied on the same infer-time fold of ExprIfThenElse (ast_infer_type.cpp:4444) to elide the dead branch — whose body references fields/operations only valid in the true branch's universe. Under lint flags, both branches survive and the dead one fails to resolve. The decs_boost case was what the bug exposed after the compiler fix landed:

daslib/decs_boost.das:245:36
        qloop.iteratorsAka[qli] := a._aka
                                    ^   field '_aka' not found in ast_core::FieldDeclaration const

Convert all 6 to static_if:

• daslib/decs_boost.das:244 — if (typeinfo has_field<_aka>(a))
• daslib/builtin.das:403 — if (typeinfo can_clone_from_const(varr))
• daslib/builtin.das:892 — if (typeinfo can_clone_from_const(val))
• daslib/builtin.das:914 — if (typeinfo can_clone_from_const(val))
• daslib/builtin.das:1183 — if (typeinfo is_pod(a))
• daslib/json_boost.das:477 — if (typeinfo can_copy(anything[0]))

"Linux x64 only"?

CI artifact: extended_checks gates the lint step to matrix.target == 'linux'. macOS / Windows builds never invoke utils/lint/main.das. Verified the bug platform-independent locally on Windows daslang.exe.

Also rolled in: 2 STYLE028 in decs_boost.das

Pre-existing master lint hits (self->implement(...) → implement(...)), forced into scope by "every changed .das file lint-clean" once the PR touches that file.

Regression coverage

tests/_issue_2830_lint_repro.das — minimal [decs_template] + from_decs_template + _where fixture. CI lint runs on changed .das files, so the fixture exercises the failing path on this PR. Without the compiler fix, lint fails at the concept_assert 30151. Without the static_if sweep, lint fails at the _aka resolution 30928. Both fixes required for the fixture to pass.

Test plan

• Bisect localizes cop.no_infer_time_folding = true as the single trigger
• WSL Ubuntu2404-CI (clang 18.1.3, Release): lint clean on all 4 repro variants (bare [decs_template], +where one field, +where multi-field, +linq_fold count chain)
• WSL regression: tests/decs 245/245, tests/json 266/266, tests/lint 8/8, utils/lint/tests 38/38
• Windows MSVC Release: MCP lint clean on all 4 changed .das files
• Pre-push hook: formatter --verify clean on 16695 files; lint clean on 3 ruleable changed files (builtin.das is in the lint utility's skip list)
• CI 9-lane matrix
• Copilot review

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[Copilot]

Pull request overview

Fixes a lint-mode regression where disabling infer-time folding (cop.no_infer_time_folding=true) + disabling optimizations (cop.no_optimizations=true) caused concept_assert/static_assert conditions and some typeinfo-guarded branches in daslib to stop folding, producing spurious typer/contract-folding errors (issue #2830).

Changes:

• Compiler: force-enable infer-time folding for ExprStaticAssert condition subtrees via a save/restore pattern in InferTypes::preVisit/visit.
• Daslib: replace 6 if (typeinfo ...) sites with static_if (typeinfo ...) so dead branches are eliminated even when infer-time folding is off.
• Tests: add a minimal lint regression fixture to ensure the failing path is exercised by CI lint on changed .das files.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/_issue_2830_lint_repro.das	Adds a lint regression fixture reproducing the issue #2830 failure mode.
src/ast/ast_infer_type.cpp	Save/force-enable/restore infer-time folding around ExprStaticAssert traversal to ensure conditions fold under lint policies.
include/daScript/ast/ast_infer_type.h	Adds savedFoldingForStaticAssert state to support the new save/restore logic.
daslib/json_boost.das	Converts a typeinfo-guarded if to static_if to avoid typing the dead branch under lint flags.
daslib/decs_boost.das	Converts if (typeinfo has_field<_aka>(a)) to static_if and fixes two STYLE028 call-site issues.
daslib/builtin.das	Converts several if (typeinfo ...) sites to static_if to ensure compile-time elimination under lint flags.

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