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feat(t27b): std.mem.eql and std.mem.indexOf compared with null, on strings - #6567
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…rings std.mem.eql(u8, a, b) on strings lowers as a == b; std.mem.indexOf(u8, h, n) == / != null calls a second synthesized fn, __t27b_str_contains, with Zig 0.16 std.mem.find semantics. Other shapes stay refused as ExprCall(std.*). Closes #6449 Refs #6063 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
…mem-2 # Conflicts: # cli/t27b/src/lower.rs
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Closes #6449
Refs #6063
What
std.mem.eql(u8, a, b)on two strings is lowered asa == b. Two literals fold; otherwise it calls__t27b_str_eql. This matches t27c's Zig backend, which prints the call verbatim.std.mem.indexOf(u8, h, n) == nulland!= nullcall a second synthesized fn,__t27b_str_contains. It follows Zig 0.16 semantics: a needle longer than the haystack is never found, and an empty needle always is.ExprCall(std.*): the index used any other way, another element type, or an operand that is not a string.cli/t27b/src/lower/stdmem.rs, with small hooks inlower.rs.Owner exception
Allowed by the owner 2026-10-05; debt to be replaced via #6198.
The local only-t27 hook (#6511) read an uncommitted line in
tools/policy/foreign-exceptions.txtthat names this PR's paths. That line is not in this PR, so the exception ends with the PR.Files
cli/t27b/src/lower.rs(hooks)cli/t27b/src/lower/stdmem.rscli/t27b/tests/stdmem.rsdocs/now/2026-10-05-t27b-stdmem.mdTests
cargo test -p t27b: all green.tests/stdmem.rs: each source was run undert27c test-reportfirst. It gives 3 pass and 2 fail there, and the same here.Corpus (
t27b corpus specs --blockers --reference <t27c> --reference-cache, jobs 8)No file loses its pass. Three files newly pass:
specs/automation/browser-pod-restart.t27,specs/port/scripts/git_commands_tasks_1_4.t27, andspecs/port/scripts/tri-search.t27.🤖 Generated with Claude Code