c3c/resources/castrules.md

Special rules for distinct types

1. Implicit conversion will happen from constant values that can be implicitly converted to the underlying type.
2. Implicit conversion will happen to the underlying type if inline.

Special rules for vectors

1. Implicit conversion will happen for non-vector numeric types, bools and pointers for init only.
2. Explicit conversion is available in all other cases.

Special rules for bool conversion in conditionals

Types that may convert to a bool, will implicitly do so in a conditional.

Bool

Implicit conversion

None

Explicit conversion

1. To float => 0.0 and 1.0
2. To int => 0 and 1 (note, there is an argument for ~0 instead)

Int

Implicit conversion

1. To float if simple expression
2. To wider int if simple expression

Explicit conversion

1. To bool/float/int always works
2. To pointer if the int is pointer sized
3. To enum (const will be range checked)
4. To bitstruct if size matches
5. To bool

Float

Implicit conversion

1. To wider float if simple expression

Explicit conversion

1. To int / float
2. To bool

Non "void*" pointer

Implicit conversion

1. To void*
2. To any
3. To slice if it is a pointer to a vector or array
4. To an interface if the pointee implements the interface.

Explicit conversion

1. To any pointer
2. To any interface
3. To an int size pointer
4. To bool

"void*" pointer

Implicit conversion

1. To any pointer

Explicit conversion

1. To a pointer sized int.
2. To bool

Slice

Implicit conversion

1. To a pointer of the same base pointer. For constant strings the ichar and char are equivalent.
2. To an array or vector of the same compile time known length if the array/vector conversion exists.

Explicit conversion

1. To a pointer of the same structure.
2. To a slice of the same structure.
3. To an array of the vector of the same compile time known length if the explicit array/vector conversion exists.

Vector

Implicit conversion

1. To a slice of the same type if the vector is constant.
2. To another vector if the base type conversion is implicit
3. To an array if the conversion would work if this was an array -> array conversion.

Explicit conversion

1. To a slice of the same structural equivalent type if the vector is constant.
2. To another vector if the base type conversion is valid.
3. To an array if the conversion would work if this was an explicit array -> array conversion.

Array

Implicit conversion

1. To a slice of the same type if the array is constant.
2. To another array of the same length but with compatible types.
3. To a vector if the conversion would work if this was an array -> array conversion.

Explicit conversion

1. To a slice of the same structural equivalent type if the array is constant.
2. To another array of the same length with structurally equivalent elements.
3. To a vector if the conversion would work if this was an explicit array -> array conversion.

Bitstruct

Implicit conversion

None

Explicit conversion

1. To the underlying type (integer or char array).
2. To bool

Struct

Implicit conversion

1. To inline member

Explicit conversion

None

Union

No conversions

"any"

Implicit conversion

1. To void*

Explicit conversion

1. To any interface
2. To any pointer
3. To bool

Interface

Implicit conversion

1. To void*
2. To any
3. To a parent interface

Explicit conversion

1. To any other interface
2. To any pointer
3. To bool

Fault

Implicit conversion

1. To anyfault

Explicit conversion

1. To a pointer sized int
2. To bool
3. To pointer

"anyfault"

Explicit conversion

1. To a pointer sized int
2. To bool
3. To pointer
4. To a fault

"typeid"

Explicit conversion

1. To a pointer size int
2. To bool
3. To pointer