Compiler Exceptions

Vyper raises one or more of the following exceptions when an issue is encountered while compiling a contract.

Whenever possible, exceptions include a source highlight displaying the location of the error within the code:

vyper.exceptions.VariableDeclarationException: line 79:17 Persistent variable undeclared: highstBid
     78     # If bid is less than highest bid, bid fails
---> 79     if (value <= self.highstBid):
     80         return False
exception ArgumentException

Raises when calling a function with invalid arguments, for example an incorrect number of positional arguments or an invalid keyword argument.

exception CallViolation

Raises on an illegal function call, such as attempting to call between two external functions.

exception ArrayIndexException

Raises when an array index is out of bounds.

exception EventDeclarationException

Raises when an event declaration is invalid.

exception EvmVersionException

Raises when a contract contains an action that cannot be performed with the active EVM ruleset.

exception FunctionDeclarationException

Raises when a function declaration is invalid, for example because of incorrect or mismatched return values.

exception ImmutableViolation

Raises when attempting to perform a change a variable, constant or definition that cannot be changed. For example, trying to update a constant, or trying to assign to a function definition.

exception InterfaceViolation

Raises when an interface is not fully implemented.

exception InvalidAttribute

Raises on a reference to an attribute that does not exist.

exception InvalidLiteral

Raises when no valid type can be found for a literal value.

def foo():
    bar: decimal = 3.123456789123456789

This example raises InvalidLiteral because the given literal value has too many decimal places and so cannot be assigned any valid Vyper type.

exception InvalidOperation

Raises when using an invalid operator for a given type.

def foo():
    a: String[10] = "hello" * 2

This example raises InvalidOperation because multiplication is not possible on string types.

exception InvalidReference

Raises on an invalid reference to an existing definition.

baz: int128

def foo():
    bar: int128 = baz

This example raises InvalidReference because baz is a storage variable. The reference to it should be written as self.baz.

exception InvalidType

Raises when using an invalid literal value for the given type.

def foo():
    bar: int128 = 3.5

This example raises InvalidType because 3.5 is a valid literal value, but cannot be cast as int128.

exception IteratorException

Raises when an iterator is constructed or used incorrectly.

exception JSONError

Raises when the compiler JSON input is malformed.

exception NamespaceCollision

Raises when attempting to assign a variable to a name that is already in use.

exception NatSpecSyntaxException

Raises when a contract contains an invalid NatSpec docstring.

vyper.exceptions.SyntaxException: line 14:5 No description given for tag '@param'
     13     @dev the feet are sticky like rice
---> 14     @param
     15     @return always True
exception NonPayableViolation

Raises when attempting to access msg.value from within a function that has not been marked as @payable.

def _foo():
    bar: uint256 = msg.value
exception OverflowException

Raises when a numeric value is out of bounds for the given type.

exception StateAccessViolation

Raises when attempting to perform a modifying action within view-only or stateless context. For example, writing to storage in a @view function, reading from storage in a @pure function.

exception StructureException

Raises on syntax that is parsable, but invalid in some way.

vyper.exceptions.StructureException: line 181:0 Invalid top-level statement
---> 181 '''
exception SyntaxException

Raises on invalid syntax that cannot be parsed.

vyper.exceptions.SyntaxException: line 4:20 invalid syntax
        3 struct Bid:
---> 4   blindedBid bytes32
        5   deposit: uint256
exception TypeMismatch

Raises when attempting to perform an action between two or more objects with known, dislike types.

def foo(:
    bar: int128 = 3
    foo: decimal = 4.2

    if foo + bar > 4:

foo has a type of int128 and bar has a type of decimal, so attempting to add them together raises a TypeMismatch.

exception UndeclaredDefinition

Raises when attempting to access an object that has not been declared.

exception VariableDeclarationException

Raises on an invalid variable declaration.

vyper.exceptions.VariableDeclarationException: line 79:17 Persistent variable undeclared: highstBid
     78     # If bid is less than highest bid, bid fails
---> 79     if (value <= self.highstBid):
     80         return False
exception VersionException

Raises when a contract version string is malformed or incompatible with the current compiler version.

exception ZeroDivisionException

Raises when a divide by zero or modulo zero situation arises.


exception CompilerPanic
$ vyper v.vy
Error compiling: v.vy
vyper.exceptions.CompilerPanic: Number of times repeated
must be a constant nonzero positive integer: 0 Please create an issue.

A compiler panic error indicates that there is a problem internally to the compiler and an issue should be reported right away on the Vyper Github page. Open an issue if you are experiencing this error. Please Open an Issue