Delphi Error E2010 — Incompatible Types

What Does This Error Mean?

Error E2010 means you tried to assign a value, pass an argument, or perform an operation using two types that Delphi cannot automatically convert between. Delphi is a strongly-typed language — types must either match or be explicitly converted. This prevents subtle bugs that happen in loosely-typed languages where values are silently misinterpreted.

Affected Models

Delphi 2005 and later
RAD Studio
Lazarus/Free Pascal (similar error)

Common Causes

Assigning a value of one type to a variable of an incompatible type (like assigning a string to an integer variable)
Passing a parameter to a function where the parameter type does not match the declared type
Comparing two values of incompatible types in an if statement
Assigning the result of a function to a variable of a different type than the function returns
Using an enumerated type value where a different enumerated type is expected

How to Fix It

Identify which two types are incompatible from the error message. Delphi usually tells you what it expected and what it found.

Double-click the error in the Messages window to jump to the exact line.
To convert a string to an integer, use StrToInt(). To convert an integer to a string, use IntToStr(). Use FloatToStr() and StrToFloat() for floating-point numbers.

These are the most common conversions. Delphi has a full set of conversion routines in SysUtils.
For numeric types, you can often cast with a type conversion: Integer(myValue) or Byte(myValue). Use this carefully — if the value is too large for the target type, it will be truncated.

Example: SmallInt(LargeIntVar) will silently lose data if LargeIntVar is above 32767.
If you are working with pointers or records and get E2010, make sure you are using the correct type throughout. Mixing Pointer with typed pointers requires explicit casting.

Example: PMyRecord(UntypdPointer) casts an untyped pointer to a specific record pointer type.
If two types look the same but are declared separately, Delphi treats them as different types. Use type compatibility rules or declare one as a type alias of the other.

Example: type TMyInt = type Integer — this creates a new distinct type. Removing the word 'type' makes it an alias that is compatible.

When to Call a Professional

E2010 is always something you can fix yourself. Delphi's type system is strict on purpose — it prevents bugs. Use explicit type conversion functions to convert between types safely.

Frequently Asked Questions

Why is Delphi so strict about types compared to other languages?

Delphi's strict typing prevents entire categories of bugs. In languages that allow implicit conversions, you can accidentally lose data, corrupt memory, or get wrong results without any warning. Delphi's compiler catches these problems at compile time — before your program runs — which is much better than discovering them as bugs in production.

What is the difference between type casting and type conversion in Delphi?

Type casting (using the type name as a function, like Integer(x)) reinterprets the raw bits without changing them. Type conversion (like IntToStr(x)) actually calculates a new value in the target type. Casting is fast but can lose data if the value does not fit. Conversion is safe but only works between compatible types.

Can I disable type checking in Delphi?

No — type checking is a fundamental part of the Delphi compiler and cannot be turned off. This is a feature, not a limitation. If you need to work with unknown types at runtime, Delphi provides TValue (in Rtti) or Variant for flexible type handling.