chore: make some functions const

[samueltardieu]

Also, enable the Clippy lint.

Summary by CodeRabbit

• New Features

  • Introduced a new linting rule to enforce stricter checks on function definitions.

• Refactor

  • Enhanced grid operations now support more flexible usage by allowing configuration toggling and inversion even in scenarios where modifications were previously restricted. This update improves performance and reliability while preserving core functionality.
  • Updated method signatures in the Grid implementation to allow invocation on immutable instances.

• Chores

  • Strengthened internal quality controls with significantly updated guidelines to ensure a robust and maintainable codebase.

[coderabbitai]

Walkthrough

The changes introduce a new linting rule in the Cargo.toml by adding missing_const_for_fn = "deny" to the Clippy configuration, enforcing stricter compile-time checks. Additionally, the signatures of three methods in src/grid.rs—enable_diagonal_mode, disable_diagonal_mode, and invert—have been updated from mutable functions to constant functions, allowing their invocation in constant contexts. The distance method in examples/sliding-puzzle.rs has also been modified to a constant method, enabling compile-time evaluation. The internal logic of these methods and other linting rules remain unchanged.

Changes

File(s)	Change Summary
Cargo.toml	Added a new linting rule: missing_const_for_fn = "deny" under [lints.clippy]
src/grid.rs	Updated method signatures for enable_diagonal_mode, disable_diagonal_mode, and invert from pub fn to pub const fn to allow calls on immutable instances
examples/sliding-puzzle.rs	Updated method signature for distance from fn distance(&self, idx: u8) -> u8 to const fn distance(&self, idx: u8) -> u8

Sequence Diagram(s)

sequenceDiagram
    participant Dev as Developer
    participant Cargo as Cargo
    participant Clippy as Clippy Linter

    Dev->>Cargo: Initiate build
    Cargo->>Clippy: Run lint checks (including missing_const_for_fn)
    Clippy-->>Cargo: Report lint errors if missing const is detected
    Cargo-->>Dev: Build fails if errors are present

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sequenceDiagram
    participant App as Application
    participant Grid as Grid Instance

    App->>Grid: Call enable_diagonal_mode() (const)
    Grid-->>App: Update diagonal_mode property to true
    App->>Grid: Call disable_diagonal_mode() (const)
    Grid-->>App: Update diagonal_mode property to false
    App->>Grid: Call invert() (const)
    Grid-->>App: Toggle dense property

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Poem

In code meadows, I hop with glee,
New lint rules shine—a strict decree.
Grid methods now gleam as const and bright,
Guiding the code with a steadfast light.
I, the CodeRabbit, dance in delight!

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📜 Recent review details

Configuration used: CodeRabbit UI
Review profile: CHILL
Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 1b20542 and d367952.

📒 Files selected for processing (3)

• Cargo.toml (1 hunks)
• examples/sliding-puzzle.rs (1 hunks)
• src/grid.rs (2 hunks)

🚧 Files skipped from review as they are similar to previous changes (2)

• Cargo.toml
• src/grid.rs

🧰 Additional context used

🧬 Code Graph Analysis (1)

examples/sliding-puzzle.rs (4)

src/grid.rs (1)

• distance (453-460)

tests/pathfinding.rs (1)

• distance (183-185)

tests/r299.rs (1)

• distance (55-57)

tests/grid.rs (1)

• distance (514-525)

🔇 Additional comments (1)

examples/sliding-puzzle.rs (1)

78-78: Good optimization to make this function const!

Making the distance method a constant function is a good practice that allows for compile-time evaluation when used in const contexts. This change aligns well with the PR's objective of making suitable functions const and with the newly added Clippy lint rule missing_const_for_fn = "deny". Since this method only reads from the struct without modifying state and performs operations that are compatible with const contexts, it's an ideal candidate for this optimization.

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