"""Generate classes representing function environments (+ related operations). If we have a nested function that has non-local (free) variables, access to the non-locals is via an instance of an environment class. Example: def f() -> int: x = 0 # Make 'x' an attribute of an environment class instance def g() -> int: # We have access to the environment class instance to # allow accessing 'x' return x + 2 x = x + 1 # Modify the attribute return g() """ from typing import Dict, Optional, Union from mypy.nodes import FuncDef, SymbolNode from mypyc.common import SELF_NAME, ENV_ATTR_NAME from mypyc.ir.ops import Call, GetAttr, SetAttr, Value from mypyc.ir.rtypes import RInstance, object_rprimitive from mypyc.ir.class_ir import ClassIR from mypyc.irbuild.builder import IRBuilder, SymbolTarget from mypyc.irbuild.targets import AssignmentTargetAttr from mypyc.irbuild.context import FuncInfo, ImplicitClass, GeneratorClass def setup_env_class(builder: IRBuilder) -> ClassIR: """Generate a class representing a function environment. Note that the variables in the function environment are not actually populated here. This is because when the environment class is generated, the function environment has not yet been visited. This behavior is allowed so that when the compiler visits nested functions, it can use the returned ClassIR instance to figure out free variables it needs to access. The remaining attributes of the environment class are populated when the environment registers are loaded. Return a ClassIR representing an environment for a function containing a nested function. """ env_class = ClassIR(f'{builder.fn_info.namespaced_name()}_env', builder.module_name, is_generated=True) env_class.attributes[SELF_NAME] = RInstance(env_class) if builder.fn_info.is_nested: # If the function is nested, its environment class must contain an environment # attribute pointing to its encapsulating functions' environment class. env_class.attributes[ENV_ATTR_NAME] = RInstance(builder.fn_infos[-2].env_class) env_class.mro = [env_class] builder.fn_info.env_class = env_class builder.classes.append(env_class) return env_class def finalize_env_class(builder: IRBuilder) -> None: """Generate, instantiate, and set up the environment of an environment class.""" instantiate_env_class(builder) # Iterate through the function arguments and replace local definitions (using registers) # that were previously added to the environment with references to the function's # environment class. if builder.fn_info.is_nested: add_args_to_env(builder, local=False, base=builder.fn_info.callable_class) else: add_args_to_env(builder, local=False, base=builder.fn_info) def instantiate_env_class(builder: IRBuilder) -> Value: """Assign an environment class to a register named after the given function definition.""" curr_env_reg = builder.add( Call(builder.fn_info.env_class.ctor, [], builder.fn_info.fitem.line) ) if builder.fn_info.is_nested: builder.fn_info.callable_class._curr_env_reg = curr_env_reg builder.add(SetAttr(curr_env_reg, ENV_ATTR_NAME, builder.fn_info.callable_class.prev_env_reg, builder.fn_info.fitem.line)) else: builder.fn_info._curr_env_reg = curr_env_reg return curr_env_reg def load_env_registers(builder: IRBuilder) -> None: """Load the registers for the current FuncItem being visited. Adds the arguments of the FuncItem to the environment. If the FuncItem is nested inside of another function, then this also loads all of the outer environments of the FuncItem into registers so that they can be used when accessing free variables. """ add_args_to_env(builder, local=True) fn_info = builder.fn_info fitem = fn_info.fitem if fn_info.is_nested: load_outer_envs(builder, fn_info.callable_class) # If this is a FuncDef, then make sure to load the FuncDef into its own environment # class so that the function can be called recursively. if isinstance(fitem, FuncDef): setup_func_for_recursive_call(builder, fitem, fn_info.callable_class) def load_outer_env(builder: IRBuilder, base: Value, outer_env: Dict[SymbolNode, SymbolTarget]) -> Value: """Load the environment class for a given base into a register. Additionally, iterates through all of the SymbolNode and AssignmentTarget instances of the environment at the given index's symtable, and adds those instances to the environment of the current environment. This is done so that the current environment can access outer environment variables without having to reload all of the environment registers. Returns the register where the environment class was loaded. """ env = builder.add(GetAttr(base, ENV_ATTR_NAME, builder.fn_info.fitem.line)) assert isinstance(env.type, RInstance), f'{env} must be of type RInstance' for symbol, target in outer_env.items(): env.type.class_ir.attributes[symbol.name] = target.type symbol_target = AssignmentTargetAttr(env, symbol.name) builder.add_target(symbol, symbol_target) return env def load_outer_envs(builder: IRBuilder, base: ImplicitClass) -> None: index = len(builder.builders) - 2 # Load the first outer environment. This one is special because it gets saved in the # FuncInfo instance's prev_env_reg field. if index > 1: # outer_env = builder.fn_infos[index].environment outer_env = builder.symtables[index] if isinstance(base, GeneratorClass): base.prev_env_reg = load_outer_env(builder, base.curr_env_reg, outer_env) else: base.prev_env_reg = load_outer_env(builder, base.self_reg, outer_env) env_reg = base.prev_env_reg index -= 1 # Load the remaining outer environments into registers. while index > 1: # outer_env = builder.fn_infos[index].environment outer_env = builder.symtables[index] env_reg = load_outer_env(builder, env_reg, outer_env) index -= 1 def add_args_to_env(builder: IRBuilder, local: bool = True, base: Optional[Union[FuncInfo, ImplicitClass]] = None, reassign: bool = True) -> None: fn_info = builder.fn_info if local: for arg in fn_info.fitem.arguments: rtype = builder.type_to_rtype(arg.variable.type) builder.add_local_reg(arg.variable, rtype, is_arg=True) else: for arg in fn_info.fitem.arguments: if is_free_variable(builder, arg.variable) or fn_info.is_generator: rtype = builder.type_to_rtype(arg.variable.type) assert base is not None, 'base cannot be None for adding nonlocal args' builder.add_var_to_env_class(arg.variable, rtype, base, reassign=reassign) def setup_func_for_recursive_call(builder: IRBuilder, fdef: FuncDef, base: ImplicitClass) -> None: """Enable calling a nested function (with a callable class) recursively. Adds the instance of the callable class representing the given FuncDef to a register in the environment so that the function can be called recursively. Note that this needs to be done only for nested functions. """ # First, set the attribute of the environment class so that GetAttr can be called on it. prev_env = builder.fn_infos[-2].env_class prev_env.attributes[fdef.name] = builder.type_to_rtype(fdef.type) if isinstance(base, GeneratorClass): # If we are dealing with a generator class, then we need to first get the register # holding the current environment class, and load the previous environment class from # there. prev_env_reg = builder.add(GetAttr(base.curr_env_reg, ENV_ATTR_NAME, -1)) else: prev_env_reg = base.prev_env_reg # Obtain the instance of the callable class representing the FuncDef, and add it to the # current environment. val = builder.add(GetAttr(prev_env_reg, fdef.name, -1)) target = builder.add_local_reg(fdef, object_rprimitive) builder.assign(target, val, -1) def is_free_variable(builder: IRBuilder, symbol: SymbolNode) -> bool: fitem = builder.fn_info.fitem return ( fitem in builder.free_variables and symbol in builder.free_variables[fitem] )