Metastatic.AST (Metastatic v0.10.4)

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M2: Meta-Model for Programming Language Abstract Syntax.

This module defines the meta-types that all language ASTs (M1 level) must conform to. Think of this as the "UML" for programming language ASTs.

Meta-Modeling Hierarchy

  • M3: Elixir type system (@type, @spec)
  • M2: This module (MetaAST) - defines what AST nodes CAN be
  • M1: Python AST, JavaScript AST, Elixir AST - what specific code IS
  • M0: Runtime execution - what code DOES

Node Structure

All MetaAST nodes are uniform 3-element tuples:

{type_atom, keyword_meta, children_or_value}

Where:

  • type_atom - Node type (e.g., :literal, :container, :function_def)
  • keyword_meta - Keyword list containing metadata (line, column, subtype, etc.)
  • children_or_value - Either a value (for leaf nodes) or list of child nodes

Third Element Semantics

The third element varies by node type:

  • Leaf nodes (literal, variable): The actual value (42, "x")
  • Composite nodes (binary_op, function_call): List of child AST nodes
  • Container nodes (container, function_def): List of body statements

Examples

# Literal integer
{:literal, [subtype: :integer, line: 10], 42}

# Variable
{:variable, [line: 5], "x"}

# Binary operation
{:binary_op, [category: :arithmetic, operator: :+],
 [{:variable, [], "x"}, {:literal, [subtype: :integer], 5}]}

# Map with pairs
{:map, [],
 [{:pair, [], [{:literal, [subtype: :symbol], :name},
               {:literal, [subtype: :string], "Alice"}]}]}

Semantic Enrichment (op_kind)

Function call nodes may include semantic metadata via the op_kind key. This metadata is added during M1 -> M2 transformation by the semantic enricher, which detects known patterns (e.g., database operations).

When present, op_kind is a keyword list with:

  • :domain - Semantic domain (e.g., :db, :http, :cache)
  • :operation - Operation type within the domain (e.g., :retrieve, :create)
  • :target - Optional target entity (e.g., "User", "orders")
  • :async - Whether the operation is asynchronous
  • :framework - Source framework (e.g., :ecto, :sqlalchemy)

Example:

{:function_call,
 [name: "Repo.get", op_kind: [domain: :db, operation: :retrieve, target: "User"]],
 [{:variable, [], "User"}, {:variable, [], "id"}]}

Analyzers can use op_kind for precise semantic detection instead of heuristics. See Metastatic.Semantic.OpKind for the full type specification.

Traversal

Use traverse/4 for walking and transforming ASTs:

AST.traverse(ast, acc, &pre/2, &post/2)

This mirrors Macro.traverse/4 from Elixir's standard library.

Summary

Types

container_type()

Container type classification.

core_type()

Node type atoms for M2.1 Core Layer - universal concepts.

db_operation()

Database operation types for op_kind metadata.

extended_type()

Node type atoms for M2.2 Extended Layer - common patterns.

literal_subtype()

Semantic subtype for literals.

meta_ast()

A MetaAST node is a 3-tuple: {type, metadata, children_or_value}.

native_type()

Node type atoms for M2.3 Native Layer - language-specific escape hatch.

node_type()

All valid node type atoms.

op_kind()

Semantic operation kind metadata added to function_call nodes. Provides precise semantic information about what a function does.

operator_category()

Category for binary/unary operators.

semantic_domain()

Semantic domain for op_kind metadata. Domains categorize operations by their high-level purpose.

structural_type()

Node type atoms for M2.2s Structural Layer - organizational constructs.

visibility()

Visibility modifier.

Functions

binary_op(category, operator, left, right, extra_meta \\ [])

Create a binary operation node.

block(statements, meta \\ [])

Create a block node.

children(arg)

Extract the children or value from a MetaAST node.

conforms?(ast)

Validate that a term conforms to the M2 meta-model.

container(type, name, body, extra_meta \\ [])

Create a container node.

container_name(arg1)

Extract the name from a container node.

function_call(name, args, extra_meta \\ [])

Create a function call node.

function_def(name, params, body, extra_meta \\ [])

Create a function definition node.

function_name(arg1)

Extract the name from a function_def node.

function_visibility(arg1)

Get the visibility of a function_def node.

get_meta(arg, key, default \\ nil)

Get a specific metadata value by key.

has_state?(arg1)

Check if a container has state (classes typically have state).

inline_match(pattern, value, meta \\ [])

Create an inline match node.

layer(type)

Get the layer classification for a node type.

leaf?(arg1)

Check if a node is a leaf node (no children to traverse).

literal(subtype, value, extra_meta \\ [])

Create a literal node.

location(arg1)

Extract location information from a MetaAST node.

map_node(pairs, meta \\ [])

Create a map node with pairs.

meta(arg)

Extract the metadata keyword list from a MetaAST node.

metadata(arg1)

Extract all metadata from a MetaAST node as a keyword list.

node_arity(ast)

Extract arity from node metadata.

node_container(ast)

Extract container name from node metadata.

node_file(ast)

Extract file path from node metadata.

node_function(ast)

Extract function name from node metadata.

node_module(ast)

Extract module name from node metadata.

node_visibility(ast)

Extract visibility from node metadata.

pair(key, value, meta \\ [])

Create a key-value pair node for maps.

postwalk(ast, acc, fun)

Traverse a MetaAST with only a post function (pre is identity).

prewalk(ast, acc, fun)

Traverse a MetaAST with only a pre function (post is identity).

put_meta(arg, key, value)

Put a metadata value by key.

traverse(ast, acc, pre, post)

Traverse a MetaAST, applying pre and post functions.

type(arg)

Extract the node type from a MetaAST node.

update_children(arg, new_children)

Update the children/value of a node.

update_meta(arg, updates)

Update multiple metadata keys at once.

variable(name, meta \\ [])

Create a variable node.

variables(ast)

Extract all variable names referenced in an AST.

with_context(ast, context)

Merge context metadata into a node's metadata.

with_location(ast, loc)

Attach location information to a MetaAST node.

Types

container_type()

@type container_type() :: :module | :class | :namespace

Container type classification.

core_type()

@type core_type() ::
  :literal
  | :variable
  | :list
  | :map
  | :pair
  | :tuple
  | :binary_op
  | :unary_op
  | :function_call
  | :conditional
  | :early_return
  | :block
  | :assignment
  | :inline_match

Node type atoms for M2.1 Core Layer - universal concepts.

db_operation()

@type db_operation() ::
  :retrieve
  | :retrieve_all
  | :query
  | :create
  | :update
  | :delete
  | :transaction
  | :preload
  | :aggregate

Database operation types for op_kind metadata.

extended_type()

@type extended_type() ::
  :loop
  | :lambda
  | :collection_op
  | :pattern_match
  | :match_arm
  | :exception_handling
  | :async_operation

Node type atoms for M2.2 Extended Layer - common patterns.

literal_subtype()

@type literal_subtype() ::
  :integer | :float | :string | :boolean | :null | :symbol | :regex

Semantic subtype for literals.

meta_ast()

@type meta_ast() :: {atom(), keyword(), term()}

A MetaAST node is a 3-tuple: {type, metadata, children_or_value}.

The type atom identifies the node kind. The metadata is a keyword list with location, subtype, and other info. The third element is either a value (leaf nodes) or list of children.

native_type()

@type native_type() :: :language_specific

Node type atoms for M2.3 Native Layer - language-specific escape hatch.

node_type()

@type node_type() :: core_type() | extended_type() | structural_type() | native_type()

All valid node type atoms.

op_kind()

@type op_kind() :: [
  domain: semantic_domain(),
  operation: atom(),
  target: String.t() | nil,
  async: boolean(),
  framework: atom() | nil
]

Semantic operation kind metadata added to function_call nodes. Provides precise semantic information about what a function does.

Fields:

  • :domain - High-level semantic category (required)
  • :operation - Specific operation within the domain (required)
  • :target - Target entity or resource (optional)
  • :async - Whether the operation is asynchronous (optional)
  • :framework - Source framework that provides this operation (optional)

Example: [domain: :db, operation: :retrieve, target: "User", framework: :ecto]

operator_category()

@type operator_category() :: :arithmetic | :comparison | :boolean

Category for binary/unary operators.

semantic_domain()

@type semantic_domain() :: :db | :http | :cache | :queue | :file | :external

Semantic domain for op_kind metadata. Domains categorize operations by their high-level purpose.

structural_type()

@type structural_type() ::
  :container
  | :function_def
  | :param
  | :attribute_access
  | :augmented_assignment
  | :property

Node type atoms for M2.2s Structural Layer - organizational constructs.

visibility()

@type visibility() :: :public | :private | :protected

Visibility modifier.

Functions

binary_op(category, operator, left, right, extra_meta \\ [])

@spec binary_op(operator_category(), atom(), meta_ast(), meta_ast(), keyword()) ::
  meta_ast()

Create a binary operation node.

Examples

iex> left = {:variable, [], "x"}
iex> right = {:literal, [subtype: :integer], 5}
iex> Metastatic.AST.binary_op(:arithmetic, :+, left, right)
{:binary_op, [category: :arithmetic, operator: :+], [{:variable, [], "x"}, {:literal, [subtype: :integer], 5}]}

block(statements, meta \\ [])

@spec block(
  [meta_ast()],
  keyword()
) :: meta_ast()

Create a block node.

Examples

iex> stmts = [{:variable, [], "x"}, {:literal, [subtype: :integer], 42}]
iex> Metastatic.AST.block(stmts)
{:block, [], [{:variable, [], "x"}, {:literal, [subtype: :integer], 42}]}

children(arg)

@spec children(meta_ast()) :: term()

Extract the children or value from a MetaAST node.

For leaf nodes (literal, variable), returns the value. For composite nodes, returns the list of children.

Examples

iex> Metastatic.AST.children({:literal, [subtype: :integer], 42})
42

iex> left = {:variable, [], "x"}
iex> right = {:literal, [subtype: :integer], 5}
iex> Metastatic.AST.children({:binary_op, [operator: :+], [left, right]})
[{:variable, [], "x"}, {:literal, [subtype: :integer], 5}]

conforms?(ast)

@spec conforms?(term()) :: boolean()

Validate that a term conforms to the M2 meta-model.

Checks that the structure is a valid 3-tuple MetaAST node with proper type, metadata, and children.

Examples

iex> Metastatic.AST.conforms?({:literal, [subtype: :integer], 42})
true

iex> Metastatic.AST.conforms?({:binary_op, [category: :arithmetic, operator: :+],
...>   [{:variable, [], "x"}, {:literal, [subtype: :integer], 5}]})
true

iex> Metastatic.AST.conforms?({:invalid_node, "data"})
false

iex> Metastatic.AST.conforms?("not a tuple")
false

container(type, name, body, extra_meta \\ [])

@spec container(container_type(), String.t(), [meta_ast()], keyword()) :: meta_ast()

Create a container node.

Examples

iex> func_def1 = {:function_def, [name: "add", params: ["x", "y"]], []}
iex> func_def2 = {:function_def, [name: "sub", params: ["x", "y"]], []}
iex> Metastatic.AST.container(:module, "MyApp.Math", [func_def1, func_def2])
{:container, [container_type: :module, name: "MyApp.Math"], [{:function_def, [name: "add", params: ["x", "y"]], []}, {:function_def, [name: "sub", params: ["x", "y"]], []}]}

container_name(arg1)

@spec container_name(meta_ast()) :: String.t() | nil

Extract the name from a container node.

Examples

iex> ast = {:container, [container_type: :module, name: "MyApp.Math"], []}
iex> Metastatic.AST.container_name(ast)
"MyApp.Math"

function_call(name, args, extra_meta \\ [])

@spec function_call(String.t(), [meta_ast()], keyword()) :: meta_ast()

Create a function call node.

Examples

iex> args = [{:variable, [], "x"}, {:literal, [subtype: :integer], 5}]
iex> Metastatic.AST.function_call("add", args)
{:function_call, [name: "add"], [{:variable, [], "x"}, {:literal, [subtype: :integer], 5}]}

function_def(name, params, body, extra_meta \\ [])

@spec function_def(String.t(), [term()], [meta_ast()], keyword()) :: meta_ast()

Create a function definition node.

Examples

iex> body = [{:binary_op, [category: :arithmetic, operator: :+],
...>   [{:variable, [], "x"}, {:variable, [], "y"}]}]
iex> Metastatic.AST.function_def("add", ["x", "y"], body)
{:function_def, [name: "add", params: ["x", "y"]], [{:binary_op, [category: :arithmetic, operator: :+], [{:variable, [], "x"}, {:variable, [], "y"}]}]}

function_name(arg1)

@spec function_name(meta_ast()) :: String.t() | nil

Extract the name from a function_def node.

Examples

iex> body = {:binary_op, [operator: :+], [{:variable, [], "x"}, {:variable, [], "y"}]}
iex> ast = {:function_def, [name: "add", params: ["x", "y"]], [body]}
iex> Metastatic.AST.function_name(ast)
"add"

function_visibility(arg1)

@spec function_visibility(meta_ast()) :: visibility()

Get the visibility of a function_def node.

Examples

iex> body = {:binary_op, [operator: :+], [{:variable, [], "x"}, {:variable, [], "y"}]}
iex> ast = {:function_def, [name: "add", visibility: :public], [body]}
iex> Metastatic.AST.function_visibility(ast)
:public

get_meta(arg, key, default \\ nil)

@spec get_meta(meta_ast(), atom(), term()) :: term()

Get a specific metadata value by key.

Examples

iex> ast = {:literal, [subtype: :integer, line: 10], 42}
iex> Metastatic.AST.get_meta(ast, :line)
10

iex> ast = {:variable, [], "x"}
iex> Metastatic.AST.get_meta(ast, :line)
nil

iex> ast = {:variable, [], "x"}
iex> Metastatic.AST.get_meta(ast, :line, 0)
0

has_state?(arg1)

@spec has_state?(meta_ast()) :: boolean()

Check if a container has state (classes typically have state).

Examples

iex> ast = {:container, [container_type: :class, name: "Counter"], []}
iex> Metastatic.AST.has_state?(ast)
true

iex> ast = {:container, [container_type: :module, name: "Math"], []}
iex> Metastatic.AST.has_state?(ast)
false

inline_match(pattern, value, meta \\ [])

@spec inline_match(meta_ast(), meta_ast(), keyword()) :: meta_ast()

Create an inline match node.

Examples

iex> pattern = {:variable, [], "x"}
iex> value = {:literal, [subtype: :integer], 42}
iex> Metastatic.AST.inline_match(pattern, value)
{:inline_match, [], [{:variable, [], "x"}, {:literal, [subtype: :integer], 42}]}

layer(type)

@spec layer(atom()) :: :core | :extended | :structural | :native | :unknown

Get the layer classification for a node type.

Returns :core, :extended, :structural, or :native.

Examples

iex> Metastatic.AST.layer(:literal)
:core

iex> Metastatic.AST.layer(:lambda)
:extended

iex> Metastatic.AST.layer(:container)
:structural

iex> Metastatic.AST.layer(:language_specific)
:native

leaf?(arg1)

@spec leaf?(meta_ast()) :: boolean()

Check if a node is a leaf node (no children to traverse).

Examples

iex> Metastatic.AST.leaf?({:literal, [subtype: :integer], 42})
true

iex> Metastatic.AST.leaf?({:variable, [], "x"})
true

iex> left = {:variable, [], "x"}
iex> right = {:literal, [subtype: :integer], 5}
iex> Metastatic.AST.leaf?({:binary_op, [], [left, right]})
false

literal(subtype, value, extra_meta \\ [])

@spec literal(literal_subtype(), term(), keyword()) :: meta_ast()

Create a literal node.

Examples

iex> Metastatic.AST.literal(:integer, 42)
{:literal, [subtype: :integer], 42}

iex> Metastatic.AST.literal(:string, "hello", line: 5)
{:literal, [subtype: :string, line: 5], "hello"}

location(arg1)

@spec location(meta_ast()) :: map() | nil

Extract location information from a MetaAST node.

Returns a map with :line, :col, :end_line, :end_col if present in metadata.

Examples

iex> ast = {:literal, [subtype: :integer, line: 10, col: 5], 42}
iex> Metastatic.AST.location(ast)
%{line: 10, col: 5}

iex> ast = {:variable, [], "x"}
iex> Metastatic.AST.location(ast)
nil

map_node(pairs, meta \\ [])

@spec map_node(
  [meta_ast()],
  keyword()
) :: meta_ast()

Create a map node with pairs.

Examples

iex> pairs = [Metastatic.AST.pair(
...>   {:literal, [subtype: :symbol], :name},
...>   {:literal, [subtype: :string], "Alice"})]
iex> Metastatic.AST.map_node(pairs)
{:map, [], [{:pair, [], [{:literal, [subtype: :symbol], :name}, {:literal, [subtype: :string], "Alice"}]}]}

meta(arg)

@spec meta(meta_ast()) :: keyword()

Extract the metadata keyword list from a MetaAST node.

Examples

iex> Metastatic.AST.meta({:literal, [subtype: :integer, line: 10], 42})
[subtype: :integer, line: 10]

iex> Metastatic.AST.meta({:variable, [], "x"})
[]

metadata(arg1)

@spec metadata(meta_ast()) :: keyword()

Extract all metadata from a MetaAST node as a keyword list.

Returns the full metadata including location, M1 context (module, function, arity, etc.), and node-specific metadata (subtype, operator, etc.).

Examples

iex> ast = {:literal, [subtype: :integer, line: 10], 42}
iex> Metastatic.AST.metadata(ast)
[subtype: :integer, line: 10]

iex> ast = {:variable, [line: 5, module: "MyApp", function: "create"], "x"}
iex> Metastatic.AST.metadata(ast)
[line: 5, module: "MyApp", function: "create"]

iex> ast = {:variable, [], "x"}
iex> Metastatic.AST.metadata(ast)
[]

node_arity(ast)

@spec node_arity(meta_ast()) :: non_neg_integer() | nil

Extract arity from node metadata.

node_container(ast)

@spec node_container(meta_ast()) :: String.t() | nil

Extract container name from node metadata.

node_file(ast)

@spec node_file(meta_ast()) :: String.t() | nil

Extract file path from node metadata.

node_function(ast)

@spec node_function(meta_ast()) :: String.t() | nil

Extract function name from node metadata.

node_module(ast)

@spec node_module(meta_ast()) :: String.t() | nil

Extract module name from node metadata.

Examples

iex> ast = {:variable, [module: "MyApp.Controller"], "x"}
iex> Metastatic.AST.node_module(ast)
"MyApp.Controller"

node_visibility(ast)

@spec node_visibility(meta_ast()) :: visibility() | nil

Extract visibility from node metadata.

pair(key, value, meta \\ [])

@spec pair(meta_ast(), meta_ast(), keyword()) :: meta_ast()

Create a key-value pair node for maps.

Examples

iex> key = {:literal, [subtype: :symbol], :name}
iex> value = {:literal, [subtype: :string], "Alice"}
iex> Metastatic.AST.pair(key, value)
{:pair, [], [{:literal, [subtype: :symbol], :name}, {:literal, [subtype: :string], "Alice"}]}

postwalk(ast, acc, fun)

@spec postwalk(meta_ast() | term(), acc, (meta_ast() | term(), acc ->
                                      {meta_ast() | term(), acc})) ::
  {meta_ast() | term(), acc}
when acc: term()

Traverse a MetaAST with only a post function (pre is identity).

Examples

{new_ast, acc} = AST.postwalk(ast, [], fn node, acc -> {node, acc} end)

prewalk(ast, acc, fun)

@spec prewalk(meta_ast() | term(), acc, (meta_ast() | term(), acc ->
                                     {meta_ast() | term(), acc})) ::
  {meta_ast() | term(), acc}
when acc: term()

Traverse a MetaAST with only a pre function (post is identity).

Examples

{new_ast, acc} = AST.prewalk(ast, [], fn node, acc -> {node, acc} end)

put_meta(arg, key, value)

@spec put_meta(meta_ast(), atom(), term()) :: meta_ast()

Put a metadata value by key.

Examples

iex> ast = {:literal, [subtype: :integer], 42}
iex> Metastatic.AST.put_meta(ast, :line, 10)
{:literal, [line: 10, subtype: :integer], 42}

iex> ast = {:variable, [line: 5], "x"}
iex> Metastatic.AST.put_meta(ast, :line, 10)
{:variable, [line: 10], "x"}

traverse(ast, acc, pre, post)

@spec traverse(meta_ast() | term(), acc, pre_fun, post_fun) ::
  {meta_ast() | term(), acc}
when acc: term(),
     pre_fun: (meta_ast() | term(), acc -> {meta_ast() | term(), acc}),
     post_fun: (meta_ast() | term(), acc -> {meta_ast() | term(), acc})

Traverse a MetaAST, applying pre and post functions.

This mirrors Macro.traverse/4 from Elixir's standard library.

  • pre is called before visiting children, receives {ast, acc}, returns {ast, acc}
  • post is called after visiting children, receives {ast, acc}, returns {ast, acc}

The traversal visits children based on the node type:

  • Leaf nodes (literal, variable): No children to visit
  • Composite nodes: Visits each child in the list
  • Non-AST values: Passed through unchanged

Examples

# Count all nodes
{_ast, count} = AST.traverse(ast, 0, fn node, acc -> {node, acc + 1} end, fn node, acc -> {node, acc} end)

# Collect all variable names
{_ast, vars} = AST.traverse(ast, [], fn
  {:variable, _, name} = node, acc -> {node, [name | acc]}
  node, acc -> {node, acc}
end, fn node, acc -> {node, acc} end)

# Transform all integers by doubling them
{new_ast, _} = AST.traverse(ast, nil, fn node, acc -> {node, acc} end, fn
  {:literal, meta, value} = node, acc ->
    if Keyword.get(meta, :subtype) == :integer do
      {{:literal, meta, value * 2}, acc}
    else
      {node, acc}
    end
  node, acc -> {node, acc}
end)

type(arg)

@spec type(meta_ast()) :: atom()

Extract the node type from a MetaAST node.

Examples

iex> Metastatic.AST.type({:literal, [subtype: :integer], 42})
:literal

iex> left = {:variable, [], "x"}
iex> right = {:literal, [subtype: :integer], 5}
iex> Metastatic.AST.type({:binary_op, [operator: :+], [left, right]})
:binary_op

update_children(arg, new_children)

@spec update_children(meta_ast(), term()) :: meta_ast()

Update the children/value of a node.

Examples

iex> old_left = {:variable, [], "x"}
iex> old_right = {:literal, [subtype: :integer], 5}
iex> ast = {:binary_op, [operator: :+], [old_left, old_right]}
iex> new_left = {:variable, [], "y"}
iex> new_right = {:literal, [subtype: :integer], 10}
iex> Metastatic.AST.update_children(ast, [new_left, new_right])
{:binary_op, [operator: :+], [{:variable, [], "y"}, {:literal, [subtype: :integer], 10}]}

update_meta(arg, updates)

@spec update_meta(
  meta_ast(),
  keyword()
) :: meta_ast()

Update multiple metadata keys at once.

Examples

iex> ast = {:literal, [subtype: :integer], 42}
iex> Metastatic.AST.update_meta(ast, line: 10, col: 5)
{:literal, [subtype: :integer, line: 10, col: 5], 42}

variable(name, meta \\ [])

@spec variable(
  String.t(),
  keyword()
) :: meta_ast()

Create a variable node.

Examples

iex> Metastatic.AST.variable("x")
{:variable, [], "x"}

iex> Metastatic.AST.variable("count", line: 10)
{:variable, [line: 10], "count"}

variables(ast)

@spec variables(meta_ast()) :: MapSet.t(String.t())

Extract all variable names referenced in an AST.

Uses traverse/4 internally to collect all variable nodes.

Examples

iex> ast = {:binary_op, [category: :arithmetic, operator: :+],
...>   [{:variable, [], "x"}, {:variable, [], "y"}]}
iex> Metastatic.AST.variables(ast)
MapSet.new(["x", "y"])

iex> ast = {:literal, [subtype: :integer], 42}
iex> Metastatic.AST.variables(ast)
MapSet.new([])

with_context(ast, context)

@spec with_context(meta_ast(), map()) :: meta_ast()

Merge context metadata into a node's metadata.

Used for attaching M1-level context like module name, function name, etc. Note: Order of merged keys is not guaranteed due to map iteration order.

Examples

iex> ast = {:variable, [line: 10], "x"}
iex> context = %{module: "MyApp"}
iex> {:variable, meta, "x"} = Metastatic.AST.with_context(ast, context)
iex> Keyword.get(meta, :module)
"MyApp"
iex> Keyword.get(meta, :line)
10

with_location(ast, loc)

@spec with_location(meta_ast(), map() | nil) :: meta_ast()

Attach location information to a MetaAST node.

Examples

iex> ast = {:literal, [subtype: :integer], 42}
iex> Metastatic.AST.with_location(ast, %{line: 10, col: 5})
{:literal, [subtype: :integer, line: 10, col: 5], 42}

iex> ast = {:variable, [], "x"}
iex> Metastatic.AST.with_location(ast, nil)
{:variable, [], "x"}