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docs_pseudo_methods.cr
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docs_pseudo_methods.cr
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{% skip_file unless flag?(:docs) %}
# This file documents pseudo-methods that are implemented by the compiler
# and can't be redefined.
# For documentation purposes, they are declared as regular methods with
# their names prefixed by `__crystal_pseudo`. This prefix is removed by
# the docs generator making it appear as the pseudo-method.
# Returns the type of an expression.
#
# ```
# typeof(1) # => Int32
# ```
#
# It accepts multiple arguments, and the result is the union of the expression types:
#
# ```
# typeof(1, "a", 'a') # => (Int32 | String | Char)
# ```
#
# The expressions passed as arguments to `typeof` do not evaluate. The compiler
# only analyzes their return type.
def __crystal_pseudo_typeof(*expression) : Class
end
# Returns the size of the given type as number of bytes.
#
# *type* must be a constant, it cannot be evaluated at runtime.
#
# ```
# sizeof(Int32) # => 4
# sizeof(Int64) # => 8
# ```
#
# For `Reference` types, the size is the same as the size of a pointer:
#
# ```
# # On a 64 bits machine
# sizeof(Pointer(Int32)) # => 8
# sizeof(String) # => 8
# ```
#
# This is because a `Reference`'s memory is allocated on the heap and a pointer
# to it is passed around. The effective size of a class can be determined using
# `instance_sizeof`.
def __crystal_pseudo_sizeof(type : Class) : Int32
end
# Returns the instance size of the given class as number of bytes.
#
# *type* must be a constant, it cannot be evaluated at runtime.
#
# ```
# instance_sizeof(String) # => 16
# instance_sizeof(Exception) # => 48
# ```
#
# See `sizeof` for determining the size of value types.
def __crystal_pseudo_instance_sizeof(type : Class) : Int32
end
# Returns a `Pointer` to the contents of a variable.
#
# *variable* must be a variable (local, instance, class or library).
#
# ```
# a = 1
# ptr = pointerof(a)
# ptr.value = 2
#
# a # => 2
# ```
def __crystal_pseudo_pointerof(variable : T) : Pointer(T) forall T
end
# Returns the byte offset of an instance variable in a struct or class type.
#
# *type* must be a constant, it cannot be evaluated at runtime.
# *variable* must be the name of an instance variable of *type*, prefixed
# by `@`.
# ```
# offsetof(String, @bytesize) # => 4
# offsetof(Exception, @message) # => 8
# offsetof(Time, @location) # => 16
# ```
def __crystal_pseudo_offsetof(type : Class, variable) : Int32
end
class Object
# Returns the boolean negation of `self`.
#
# ```
# !true # => false
# !false # => true
# !nil # => true
# !1 # => false
# !"foo" # => false
# ```
#
# This method is a unary operator and usually written in prefix notation
# (`!foo`) but it can also be written as a regular method call (`foo.!`).
def __crystal_pseudo_! : Bool
end
# Returns `true` if `self` inherits or includes *type*.
# *type* must be a constant, it cannot be evaluated at runtime.
#
# ```
# a = 1
# a.class # => Int32
# a.is_a?(Int32) # => true
# a.is_a?(String) # => false
# a.is_a?(Number) # => true
# a.is_a?(Int32 | String) # => true
# ```
def __crystal_pseudo_is_a?(type : Class) : Bool
end
# Returns `true` if `self` is `Nil`.
#
# ```
# 1.nil? # => false
# nil.nil? # => true
# ```
#
# This method is equivalent to `is_a?(Nil)`.
def __crystal_pseudo_nil? : Bool
end
# Returns `self`.
#
# The type of this expression is restricted to *type* by the compiler.
# *type* must be a constant, it cannot be evaluated at runtime.
#
# If *type* is not a valid restriction for the expression type, it
# is a compile-time error.
# If *type* is a valid restriction for the expression, but `self` can't
# be restricted to *type*, it raises at runtime.
# *type* may be a wider restriction than the expression type, the resulting
# type is narrowed to the minimal restriction.
#
# ```
# a = [1, "foo"][0]
# typeof(a) # => Int32 | String
#
# typeof(a.as(Int32)) # => Int32
# a.as(Int32) # => 1
#
# typeof(a.as(Bool)) # Compile Error: can't cast (Int32 | String) to Bool
#
# typeof(a.as(String)) # => String
# a.as(String) # Runtime Error: cast from Int32 to String failed
#
# typeof(a.as(Int32 | Bool)) # => Int32
# a.as(Int32 | Bool) # => 1
# ```
def __crystal_pseudo_as(type : Class)
end
# Returns `self` or `nil` if can't be restricted to *type*.
#
# The type of this expression is restricted to *type* by the compiler.
# If *type* is not a valid type restriction for the expression type, then
# it is restricted to `Nil`.
# *type* must be a constant, it cannot be evaluated at runtime.
#
# ```
# a = [1, "foo"][0]
# typeof(a) # => Int32 | String
#
# typeof(a.as?(Int32)) # => Int32 | Nil
# a.as?(Int32) # => 1
#
# typeof(a.as?(Bool)) # => Nil
# a.as?(Bool) # => nil
#
# typeof(a.as?(String)) # => String | Nil
# a.as?(String) # nil
#
# typeof(a.as?(Int32 | Bool)) # => Int32 | Nil
# a.as?(Int32 | Bool) # => 1
# ```
def __crystal_pseudo_as?(type : Class)
end
# Returns `true` if method *name* can be called on `self`.
#
# *name* must be a symbol literal, it cannot be evaluated at runtime.
#
# ```
# a = 1
# a.responds_to?(:abs) # => true
# a.responds_to?(:size) # => false
# ```
def __crystal_pseudo_responds_to?(name : Symbol) : Bool
end
end