Warning Codes

This document lists the warning codes that the YaoXiang compiler may produce. Warnings do not prevent compilation, but may indicate potential issues in the code.

Configuration

Warning behavior can be configured via yaoxiang.toml:

[lint]
# Dead code warning level: off | warn | deny
dead-code = "warn"

• off: Disable the warning
• warn: Show the warning (default)
• deny: Treat the warning as an error

Warning List

W1001: Unused exported function

Reason: The exported function is never called by any code.

pub dead_function: () -> Void = { }  // W1001: unused exported function

main: () -> Void = {
    // dead_function is never called
}

Suggestions:

• If the function does not need to be used externally, remove the pub modifier
• If the function needs to be kept but is temporarily unused, set dead-code = "off" in the configuration

---

W1002: Unused exported type

Reason: The exported type (type alias or custom type) is never used.

Example:

DeadType: Type = Int  // W1002: unused exported type

main: () -> Void = {
    x = 42
}

Suggestions:

• If the type needs to be exported but is temporarily unused, ignore this warning

---

W1003: Unused import

Reason: The module or symbol imported by a use statement is never used.

use std.json  // W1003: unused import

main: () -> Void = {
    // json module is never used
}

Suggestions:

• Remove unused imports to keep the code clean
• If the import needs to be kept (for side effects), consider using use std.json.* or add a comment explaining why

---

W1004: Unused exported variable

Reason: The variable exported with pub is never read.

Example:

pub dead_var = 42  // W1004: unused exported variable

main: () -> Void = {
    // dead_var is never read
}

Suggestions:

• Remove the unnecessary pub modifier
• If the variable needs to be exported but is temporarily unused, ignore this warning

---

W1005: Unused exported method

Reason: The method exported on a type is never called.

Example:

Foo: Type = { value: Int }

pub Foo.dead_method: (self: Foo) -> Void = { }  // W1005: unused exported method

main: () -> Void = {
    foo = Foo(1)
    // dead_method is never called
}

Suggestions:

• Remove the unnecessary pub modifier
• If the method needs to be kept but is temporarily unused, ignore this warning

---

W1063: const generic constraint cannot be evaluated

Reason: The value constraint of a const generic parameter cannot be evaluated at compile-time.

Message: const generic constraint cannot be evaluated: `{constraint}` ({var} = {value})

BadArray(Int, n)  // n is not a compile-time constant

Suggestions:

• Ensure the const parameter is a compile-time constant

---

W1080: Compile-time proof degradation

Reason: The constraint could not be proven at compile-time and has been degraded to a runtime check.

Message: Constraint could not be proven at compile-time, has been degraded to a runtime check

Suggestions:

• Consider adding a proof function to improve safety

---

Warning Levels Explained

Level	Effect
off	Completely disable this warning
warn	Show the warning but continue compilation (default)
deny	Treat the warning as an error, blocking compilation

Use Cases

• During development: Use the warn level to learn about potential issues in the code
• Before release: Use the deny level to ensure no unused code remains
• Legacy code: Use the off level to temporarily ignore warnings

---

Difference from Error Codes

Warning codes use the W prefix (e.g., W1001), while error codes use the E prefix (e.g., E1001).

• Error: Blocks compilation and must be fixed
• Warning: Indicates a potential issue and is optional to fix