Semantic Errors (E2xxx)

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These errors occur during Stage 3 (Semantic Analysis) when the compiler validates types, scopes, and contract structure.

Code	Name	Description	Common Cause
E2001	UndefinedVariable	Undefined variable	Typo in variable name, missing declaration
E2002	TypeMismatch	Type mismatch	Assigning incompatible types (e.g., address to uint256)
E2003	DuplicateDefinition	Duplicate definition	Two functions/variables with the same name in the same scope
E2004	UndefinedFunction	Undefined function	Calling a function that does not exist
E2005	UndefinedType	Undefined type	Using a struct or contract name that is not defined
E2006	InvalidAssignment	Invalid assignment	Assigning to a constant or read-only value
E2007	ImmutableModification	Cannot modify immutable value	Writing to an immutable or constant variable
E2008	VisibilityError	Visibility error	Calling a private function from outside its contract
E2009	InvalidOverride	Invalid override	Override without virtual/override keywords
E2010	MissingReturn	Missing return statement	Non-void function path without return
E2011	UnreachableCode	Unreachable code	Code after return, revert, or require(false)
E2012	UnusedVariable	Unused variable	Declared variable never read
E2013	UnusedFunction	Unused function	Internal function never called
E2014	ShadowedVariable	Variable shadows outer scope	Local variable hides a state variable
E2015	InvalidModifier	Invalid modifier	Modifier used incorrectly or on wrong function type

Example: E2002 TypeMismatch

error[E2002]: type mismatch: expected uint256, found address
  --> MyContract.sol:15:5
   |
15 |     uint256 x = msg.sender;
   |     ^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: use explicit cast: uint256(uint160(msg.sender))

Fix: Correct the type usage. In Neo DevPack for Solidity, addresses and integers are distinct types just as in standard Solidity. Use explicit casts when conversion is intentional.

Example: E2003 DuplicateDefinition

error[E2003]: duplicate definition: function 'transfer' already defined
  --> MyContract.sol:25:5

Fix: Rename one of the conflicting definitions, or use function overloading with different parameter signatures.