View Source Macro.Env (Elixir v1.12.0)

A struct that holds compile time environment information.

The current environment can be accessed at any time as __ENV__/0. Inside macros, the caller environment can be accessed as __CALLER__/0.

An instance of Macro.Env must not be modified by hand. If you need to create a custom environment to pass to Code.eval_quoted/3, use the following trick:

def make_custom_env do
  import SomeModule, only: [some_function: 2]
  alias A.B.C
  __ENV__
end

You may then call make_custom_env() to get a struct with the desired imports and aliases included.

It contains the following fields:

  • aliases - a list of two-element tuples, where the first element is the aliased name and the second one the actual name
  • context - the context of the environment; it can be nil (default context), :guard (inside a guard) or :match (inside a match)
  • context_modules - a list of modules defined in the current context
  • file - the current file name as a binary
  • function - a tuple as {atom, integer}, where the first element is the function name and the second its arity; returns nil if not inside a function
  • functions - a list of functions imported from each module
  • line - the current line as an integer
  • macro_aliases - a list of aliases defined inside the current macro
  • macros - a list of macros imported from each module
  • module - the current module name
  • requires - the list of required modules

The following fields are private to Elixir's macro expansion mechanism and must not be accessed directly:

  • contextual_vars
  • current_vars
  • lexical_tracker
  • prematch_vars
  • tracers
  • unused_vars

The following fields are deprecated and must not be accessed or relied on:

  • vars - a list keeping all defined variables as {var, context}

Link to this section Summary

Functions

Checks if a variable belongs to the environment.

Returns whether the compilation environment is currently inside a guard.

Returns whether the compilation environment is currently inside a match clause.

Returns a keyword list containing the file and line information as keys.

Returns the environment stacktrace.

Returns a Macro.Env in the match context.

Returns a list of variables in the current environment.

Link to this section Types

@type aliases() :: [{module(), module()}]
@type context() :: :match | :guard | nil
@type context_modules() :: [module()]
@type file() :: binary()
@type functions() :: [{module(), [name_arity()]}]
@type lexical_tracker() :: pid() | nil
@type line() :: non_neg_integer()
@type macro_aliases() :: [{module(), {term(), module()}}]
@type macros() :: [{module(), [name_arity()]}]
@type name_arity() :: {atom(), arity()}
@type requires() :: [module()]
@type t() :: %Macro.Env{
  aliases: aliases(),
  context: context(),
  context_modules: context_modules(),
  contextual_vars: contextual_vars(),
  current_vars: current_vars(),
  file: file(),
  function: name_arity() | nil,
  functions: functions(),
  lexical_tracker: lexical_tracker(),
  line: line(),
  macro_aliases: macro_aliases(),
  macros: macros(),
  module: module(),
  prematch_vars: prematch_vars(),
  unused_vars: unused_vars(),
  requires: requires(),
  tracers: tracers(),
  vars: vars()
}
@type variable() :: {atom(), atom() | term()}

Link to this section Functions

Link to this function

has_var?(env, var)

View Source (since 1.7.0)
@spec has_var?(t(), variable()) :: boolean()

Checks if a variable belongs to the environment.

@spec in_guard?(t()) :: boolean()

Returns whether the compilation environment is currently inside a guard.

@spec in_match?(t()) :: boolean()

Returns whether the compilation environment is currently inside a match clause.

@spec location(t()) :: keyword()

Returns a keyword list containing the file and line information as keys.

@spec stacktrace(t()) :: list()

Returns the environment stacktrace.

@spec to_match(t()) :: t()

Returns a Macro.Env in the match context.

@spec vars(t()) :: [variable()]

Returns a list of variables in the current environment.

Each variable is identified by a tuple of two elements, where the first element is the variable name as an atom and the second element is its context, which may be an atom or an integer.