✨ feat(mq-lang): add destructuring assignment for let/var by harehare · Pull Request #1466 · harehare/mq

harehare · 2026-03-18T03:10:19Z

Support array and dict patterns on the left-hand side of let/var declarations.

Copilot

Pull request overview

Adds destructuring patterns to let/var declarations in mq-lang, with corresponding runtime evaluation, parsing updates (AST + CST), HIR lowering changes, and documentation/tests to validate the new syntax.

Changes:

Extend AST/CST parsers so let/var LHS can be an array/dict pattern (e.g. let [a, b] = ..., let {x} = ...).
Evaluate let/var by matching the RHS value against a pattern and binding all extracted names (or erroring on mismatch).
Update HIR lowering + docs + integration/property tests for the new pattern forms.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
docs/books/src/reference/variables.md	Documents destructuring declarations for `let`/`var`, including array/dict/rest examples.
crates/mq-run/tests/integration_tests.rs	Adds CLI-level integration tests for destructuring success cases.
crates/mq-lang/tests/property_based_tests.rs	Updates generators to build `Let`/`Var` with `AstPattern::Ident(...)`.
crates/mq-lang/src/module.rs	Updates module parsing tests to construct `Let` with `Pattern::Ident(...)`.
crates/mq-lang/src/macro_expand.rs	Propagates patterns through macro expansion/substitution for `Let`/`Var`.
crates/mq-lang/src/lib.rs	Re-exports `AstPattern`.
crates/mq-lang/src/eval.rs	Implements destructuring binding via `match_pattern` for `Let`/`Var` (and module var loading).
crates/mq-lang/src/error/runtime.rs	Adds `RuntimeError::DestructuringFailed`.
crates/mq-lang/src/error.rs	Adds diagnostic/help text for destructuring failures.
crates/mq-lang/src/cst/parser.rs	Parses `let`/`var` LHS as pattern nodes when starting with `[`/`{`.
crates/mq-lang/src/ast/parser.rs	Parses `let`/`var` LHS into `Pattern` (array/dict/ident).
crates/mq-lang/src/ast/node.rs	Changes `Expr::Let/Var` to store a `Pattern` instead of an identifier.
crates/mq-lang/src/ast/code.rs	Formats `let`/`var` patterns back to source; adds unit tests for pattern formatting.
crates/mq-hir/src/hir/lower.rs	Lowers `let`/`var` destructuring LHS via `add_pattern_expr`.

crates/mq-lang/src/eval.rs

crates/mq-lang/src/cst/parser.rs

crates/mq-run/tests/integration_tests.rs

crates/mq-lang/src/eval.rs

crates/mq-lang/src/ast/parser.rs

crates/mq-hir/src/hir/lower.rs

codspeed-hq · 2026-03-18T03:19:18Z

Merging this PR will not alter performance

✅ 29 untouched benchmarks

_{Comparing feat/destructuring-assignment (3cc01b9) with main (a5a8514)¹}

No successful run was found on main (8acb567) during the generation of this report, so a5a8514 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

… completions and hover responses

Copilot

Pull request overview

Adds destructuring patterns to let/var declarations in mq-lang, with corresponding updates to parsing/AST, runtime evaluation, LSP UX, docs, and integration tests.

Changes:

Extend AST/CST parsers and AST node model so let/var accept array/dict patterns (plus array rest ..).
Update evaluator/module loading to bind variables produced by pattern matching, and introduce a runtime error for pattern mismatch.
Surface pattern-bound variables in LSP hover/completions and document/test the new syntax.

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
docs/books/src/reference/variables.md	Documents destructuring usage for `let`/`var` (array/dict/rest)
crates/mq-run/tests/integration_tests.rs	Adds CLI-level integration tests for destructuring declarations
crates/mq-lsp/src/hover.rs	Includes `PatternVariable` symbols in hover output
crates/mq-lsp/src/completions.rs	Includes `PatternVariable` symbols in completion items
crates/mq-lang/tests/property_based_tests.rs	Updates generators to use `AstPattern::Ident` for let/var
crates/mq-lang/src/module.rs	Updates module parsing test expectations for pattern-based `let`
crates/mq-lang/src/macro_expand.rs	Propagates pattern-based `let`/`var` through macro expansion/substitution
crates/mq-lang/src/lib.rs	Re-exports `AstPattern` from the AST module
crates/mq-lang/src/eval.rs	Implements pattern binding for `let`/`var` and module var initialization
crates/mq-lang/src/error/runtime.rs	Adds `RuntimeError::DestructuringFailed`
crates/mq-lang/src/error.rs	Adds diagnostic help text for destructuring mismatch
crates/mq-lang/src/cst/parser.rs	Allows LHS pattern nodes in CST `let`/`var` declarations
crates/mq-lang/src/ast/parser.rs	Parses `let`/`var` LHS as a `Pattern` (ident/array/dict)
crates/mq-lang/src/ast/node.rs	Changes `Expr::{Let,Var}` to store `Pattern` instead of `IdentWithToken`
crates/mq-lang/src/ast/code.rs	Updates AST-to-code formatting to print patterns for `let`/`var`
crates/mq-hir/src/hir/lower.rs	Lowers destructuring `let`/`var` into pattern-related HIR symbols

crates/mq-run/tests/integration_tests.rs

crates/mq-lang/src/eval.rs

crates/mq-hir/src/hir/lower.rs

crates/mq-lang/src/cst/parser.rs

…ndling

…g and constraints

…constraints

…ray and dict patterns

Copilot

Pull request overview

Adds destructuring patterns to let/var declarations in mq-lang, and wires the feature through parsing → evaluation → HIR → type checking → LSP, with docs and CLI integration tests to validate behavior end-to-end.

Changes:

Extend CST/AST parsing and AST printing to allow array/dict patterns on let/var LHS.
Implement runtime destructuring via pattern matching in the evaluator, with a dedicated runtime error on mismatch.
Add HIR + type-checker + LSP support for destructuring bindings, plus new integration tests and reference docs.

Reviewed changes

Copilot reviewed 26 out of 26 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
docs/books/src/reference/variables.md	Documents destructuring `let`/`var` syntax with examples.
crates/mq-run/tests/integration_tests.rs	Adds CLI integration tests for array/dict destructuring and mutation via `var`.
crates/mq-lsp/src/semantic_tokens.rs	Classifies destructuring bindings for semantic token output.
crates/mq-lsp/src/inlay_hints.rs	Includes destructuring bindings in type inlay hints.
crates/mq-lsp/src/hover.rs	Adds hover support for destructuring-related symbol kinds.
crates/mq-lsp/src/document_symbol.rs	Treats destructuring bindings similarly to variables for document symbols.
crates/mq-lsp/src/completions.rs	Exposes destructuring-related symbol kinds in completions.
crates/mq-lang/tests/property_based_tests.rs	Updates AST generators to build `Let/Var` using `AstPattern`.
crates/mq-lang/src/module.rs	Updates module test AST to use `Pattern::Ident` for `Let`.
crates/mq-lang/src/macro_expand.rs	Updates macro expansion/substitution to clone `Let/Var` patterns.
crates/mq-lang/src/lib.rs	Re-exports `AstPattern`.
crates/mq-lang/src/eval.rs	Implements destructuring semantics for `let/var` via `match_pattern`.
crates/mq-lang/src/error/runtime.rs	Adds `RuntimeError::DestructuringFailed`.
crates/mq-lang/src/error.rs	Adds a diagnostic help message for destructuring failures.
crates/mq-lang/src/cst/parser.rs	Parses `let/var` LHS as either ident or pattern (`[]`/`{}`).
crates/mq-lang/src/ast/parser.rs	Parses `let/var` patterns into `Pattern` (array/dict/ident).
crates/mq-lang/src/ast/node.rs	Changes `Expr::Let/Var` to store `Pattern` instead of `IdentWithToken`.
crates/mq-lang/src/ast/code.rs	Prints `let/var` with patterns via `format_pattern` + adds formatting tests.
crates/mq-hir/src/symbol.rs	Introduces `SymbolKind::DestructuringBinding` and treats it as variable-like.
crates/mq-hir/src/resolve.rs	Includes `DestructuringBinding` in resolution priority rules.
crates/mq-hir/src/hir/lower.rs	Lowers destructuring `let/var` into `DestructuringBinding` + pattern variable symbols.
crates/mq-hir/src/hir.rs	Adds a HIR test asserting destructuring lowering structure.
crates/mq-check/src/constraint/pipe.rs	Propagates piped input through destructuring binding initializers like variables.
crates/mq-check/src/constraint/helpers.rs	Adds helper to collect `PatternVariable` descendants for destructuring constraints.
crates/mq-check/src/constraint/categories.rs	Categorizes `DestructuringBinding` for constraint passes.
crates/mq-check/src/constraint.rs	Adds constraint generation logic for destructuring bindings (array/dict).

Comments suppressed due to low confidence (1)

crates/mq-lsp/src/semantic_tokens.rs:94

SymbolKind::DestructuringBinding is emitted as a semantic token using its full text_range (currently the entire pattern range like [a, b]). This will overlap with the Pattern/PatternVariable tokens inside the pattern, which violates LSP semantic token requirements (tokens must be non-overlapping) and can break highlighting in clients. Suggestion: don’t produce semantic tokens for DestructuringBinding (or ensure its range does not overlap, e.g. by not assigning it a text_range in HIR).

                mq_hir::SymbolKind::Variable
                | mq_hir::SymbolKind::DestructuringBinding
                | mq_hir::SymbolKind::Symbol
                | mq_hir::SymbolKind::MatchArm
                | mq_hir::SymbolKind::Pattern
                | mq_hir::SymbolKind::PatternVariable
                | mq_hir::SymbolKind::Ident => token_type(ls_types::SemanticTokenType::VARIABLE),

crates/mq-check/src/constraint.rs

…les in symbol visibility

…estructuring with rest elements

…key bindings and improve pattern handling

Copilot

Pull request overview

Adds destructuring patterns to mq’s let/var declarations, wiring the feature through parsing, runtime evaluation, HIR/lowering, type inference, and editor tooling.

Changes:

Extend CST/AST parsing so let/var accept array/dict patterns on the LHS.
Implement runtime binding of destructured values (and a new runtime error on mismatch).
Teach HIR, type constraints, and LSP/wasm tooling to recognize destructuring-related symbols; add integration/type-check tests and docs.

Reviewed changes

Copilot reviewed 28 out of 28 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
docs/books/src/reference/variables.md	Documents destructuring for `let`/`var` with examples.
crates/mq-wasm/src/script.rs	Shows inlay hints for destructuring bindings/pattern variables in wasm tooling.
crates/mq-run/tests/integration_tests.rs	Adds CLI integration tests for destructuring success cases + regression.
crates/mq-lsp/src/semantic_tokens.rs	Classifies destructuring-related symbols for semantic highlighting.
crates/mq-lsp/src/inlay_hints.rs	Includes destructuring bindings in LSP inlay-hints eligibility.
crates/mq-lsp/src/hover.rs	Adds hover support for destructuring bindings/pattern variables.
crates/mq-lsp/src/document_symbol.rs	Includes destructuring binding symbols in document-symbol output.
crates/mq-lsp/src/completions.rs	Includes destructuring binding/pattern variables in completion candidates.
crates/mq-lang/tests/property_based_tests.rs	Updates generators to match new `Let/Var(Pattern, ...)` AST shape.
crates/mq-lang/src/module.rs	Updates module tests/fixtures for new `let` AST representation.
crates/mq-lang/src/macro_expand.rs	Updates macro expansion/substitution to preserve `let/var` patterns.
crates/mq-lang/src/lib.rs	Re-exports `AstPattern`.
crates/mq-lang/src/eval.rs	Implements destructuring binding evaluation for `let`/`var`.
crates/mq-lang/src/error/runtime.rs	Adds `RuntimeError::DestructuringFailed`.
crates/mq-lang/src/error.rs	Adds diagnostic/help text for destructuring failure runtime error.
crates/mq-lang/src/cst/parser.rs	Parses pattern forms (`[...]` / `{...}`) on `let/var` LHS in CST.
crates/mq-lang/src/ast/parser.rs	Parses `let/var` LHS into `Pattern` (array/dict/ident).
crates/mq-lang/src/ast/node.rs	Changes `Expr::Let/Var` to store `Pattern` instead of `IdentWithToken`; defines `Pattern`.
crates/mq-lang/src/ast/code.rs	Formats `let/var` patterns back to code; adds format tests for patterns.
crates/mq-hir/src/symbol.rs	Adds `DestructuringBinding`; refines `Pattern/PatternVariable` kinds.
crates/mq-hir/src/resolve.rs	Updates symbol priority rules for new symbol kinds.
crates/mq-hir/src/hir/lower.rs	Lowers destructuring `let/var` into `DestructuringBinding` + pattern children; tracks rest bindings and dict keys.
crates/mq-hir/src/hir.rs	Updates HIR tests and adds destructuring-binding HIR test coverage.
crates/mq-check/tests/type_errors_test.rs	Adds type-check tests for dict destructuring (shorthand + explicit key).
crates/mq-check/src/constraint/pipe.rs	Propagates piped input to destructuring initializer like normal variables.
crates/mq-check/src/constraint/helpers.rs	Adds helper to collect `PatternVariable` descendants for constraints.
crates/mq-check/src/constraint/categories.rs	Categorizes destructuring binding / pattern variable symbols for constraint passes.
crates/mq-check/src/constraint.rs	Adds constraint generation for destructuring bindings (array + dict).

crates/mq-check/src/constraint.rs

crates/mq-lang/src/eval.rs

crates/mq-hir/src/symbol.rs

crates/mq-lsp/src/completions.rs

crates/mq-lsp/src/document_symbol.rs

✨ feat(mq-lang): add destructuring assignment for let/var

fb89bbc

Support array and dict patterns on the left-hand side of let/var declarations.

Copilot AI review requested due to automatic review settings March 18, 2026 03:10

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harehare added 2 commits March 18, 2026 13:39

✨ feat(mq-lang): enhance destructuring assignment handling in evaluator

2641da1

✨ feat(mq-lang): extend symbol handling to include PatternVariable in…

679bb4d

… completions and hover responses

Copilot AI review requested due to automatic review settings March 18, 2026 06:16

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harehare added 4 commits March 18, 2026 18:25

🐛 fix(evaluator): correct token reference in destructuring failure ha…

f4d94f2

…ndling

✨ feat(hir): add support for destructuring bindings in symbol handlin…

f9cde9f

…g and constraints

✨ feat(constraint): enhance destructuring binding handling in symbol …

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…constraints

✨ feat(constraint): improve handling of destructuring bindings for ar…

81a8fab

…ray and dict patterns

Copilot AI review requested due to automatic review settings March 18, 2026 10:45

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harehare added 3 commits March 18, 2026 21:10

✨ feat(inlay-hints): add support for destructuring and pattern variab…

c3a8b0f

…les in symbol visibility

✨ feat(constraint): update handling of pattern variables to support d…

590060c

…estructuring with rest elements

✨ feat(constraint): enhance dict destructuring support with explicit …

3cc01b9

…key bindings and improve pattern handling

Copilot AI review requested due to automatic review settings March 18, 2026 12:54

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harehare merged commit ec24cb6 into main Mar 18, 2026
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harehare deleted the feat/destructuring-assignment branch March 18, 2026 13:08

BrewTestBot mentioned this pull request Mar 18, 2026

mq 0.5.20 Homebrew/homebrew-core#272991

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Merging this PR will not alter performance

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codspeed-hq bot commented Mar 18, 2026 •

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