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Pull request overview
This PR implements "tuple mode" for the mq-check type checker. When the --tuple flag is enabled, heterogeneous array literals (e.g., [1, "hello"]) are inferred as Tuple(number, string) instead of a generic Array('a). This enables precise per-element type tracking so that v[0] resolves to number and v[1] resolves to string, while homogeneous arrays remain unaffected. The PR also renames the crate from mq-typechecker to mq-check and adds a large suite of new integration tests and builtin type-registration tests.
Changes:
- Added
Type::Tuple(Vec<Type>)variant to the type system with full support across unification, substitution, display, and overload scoring. - Added the
--tupleCLI flag andTypeCheckerOptions::tuplefield, plus deferred tuple-index access resolution inlib.rs. - Added two new test files (
integration_test.rs,error_location_test.rs) and a newbuiltin.rswith comprehensive type signatures and tests; renamed crate frommq-typecheckertomq-checkinCargo.toml.
Reviewed changes
Copilot reviewed 9 out of 15 changed files in this pull request and generated no comments.
Show a summary per file
| File | Description |
|---|---|
crates/mq-check/src/types.rs |
Adds Type::Tuple variant; implements display, unification, match scoring, substitution, free-var collection |
crates/mq-check/src/unify.rs |
Tuple-to-tuple and tuple-to-array unification cases; occurs check and substitution for Tuple |
crates/mq-check/src/constraint.rs |
Generates Tuple type for heterogeneous arrays in tuple mode; defers tuple index access resolution |
crates/mq-check/src/lib.rs |
Adds TypeCheckerOptions::tuple; drives resolve_deferred_tuple_accesses post-unification |
crates/mq-check/src/infer.rs |
Adds DeferredTupleAccess struct and context fields/methods |
crates/mq-check/src/narrowing.rs |
New file: flow-sensitive type narrowing from predicates and structural selectors |
crates/mq-check/src/builtin.rs |
New file: all builtin function type signatures, organized by category |
crates/mq-check/src/main.rs |
Adds --tuple CLI flag; refactors check_file to use CheckOptions struct |
crates/mq-check/README.md |
Documents tuple mode, all CLI options |
crates/mq-check/Cargo.toml |
New manifest for mq-check |
Cargo.toml |
Replaces mq-typechecker with mq-check in workspace members |
crates/mq-check/tests/type_errors_test.rs |
Adds helper + tests for tuple mode |
crates/mq-check/tests/integration_test.rs |
Large new integration test file covering the type checker |
crates/mq-check/tests/error_location_test.rs |
New tests for error location and message readability |
Comments suppressed due to low confidence (1)
crates/mq-check/src/types.rs:348
- There is a potential integer division by zero panic on this line. When both
elems1andelems2are empty tuples (Type::Tuple(vec![])), the guardelems1.len() == elems2.len()passes (0 == 0),totalis 0, and thentotal / elems1.len() as u32evaluates to0 / 0, which panics in Rust in both debug and release builds.
The fix is to guard against the empty-tuple case, for example by returning Some(20) early when elems1.is_empty(), or by using elems1.len().max(1) in the divisor.
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