erg/doc/EN/compiler/errors.md

Erg Compiler Errors

AssignError

Raised when attempting to rewrite an immutable variable.

AttributeError

Raised when trying to access an attribute that does not exist.

PurityError

Raised when writing code that causes side effects in scopes (functions, immutable types, etc.) where side effects are not allowed.

MoveError

Raised when you try to access a variable that has already been moved.

BorrowError

Raised when an attempt is made to obtain another variable reference while a borrow exists for an object.

CyclicError

Raised when there is an apparent non-stop cycle.

i: Int = i

f(): Int = g()
g() = f()

h(): Int = module::h()

T = U
U = T

BytecodeError

Raised if the bytecode read is corrupt.

CompileSystemError

Raised when an error occurs inside the compiler.

EnvironmentError

Raised when there is no access permission during installation.

FeatureError

Raised when an experimental feature that is not officially provided is detected.

ImportError

IndentationError

Raised when an invalid indentation is detected. Derived from SyntaxError.

NameError

Raised when accessing a variable that does not exist.

NotImplementedError

Raised when calling an API that has a definition but no implementation. Derived from TypeError.

PatternError

Raised when an invalid pattern is detected. Derived from SyntaxError.

SyntaxError

Raised when an invalid syntax is detected.

TabError

Raised when a tab character is used for indentation/space. Derived from SyntaxError.

TypeError

Raised when the object type does not match.

UnboundLocalError

Raised when a variable is used before it is defined. More precisely, it occurs when a variable defined in a scope is used before it is defined.

i = 0
f x =
    y = i + x
    i = 1
    y + i

In this code, the i in y = i + x is an undefined variable. However, if it is a constant, it can be called in another function before it is defined.

f() = g()
g() = f()

Erg Compiler Warnings

SyntaxWarning

This happens when syntactically sound but redundant or uncommon code is detected (e.g., unnecessary ()).

if (True): # SyntaxWarning: unnecessary parentheses
    ...

DeprecationWarning

Raised if the referenced object is deprecated. (Developers should always provide an alternative Hint when raising this Warning.)

FutureWarning

Raised when code is detected that may cause problems in the future. This warning is caused by version compatibility issues (including libraries) or changes in syntax or API.

ImportWarning