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# Copyright 2019 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Main driver for the Emboss front-end.
The parse_emboss_file function performs a complete parse of the specified file,
and returns an IR or formatted error message.
"""
import collections
from compiler.front_end import attribute_checker
from compiler.front_end import constraints
from compiler.front_end import dependency_checker
from compiler.front_end import expression_bounds
from compiler.front_end import lr1
from compiler.front_end import module_ir
from compiler.front_end import parser
from compiler.front_end import symbol_resolver
from compiler.front_end import synthetics
from compiler.front_end import tokenizer
from compiler.front_end import type_check
from compiler.front_end import write_inference
from compiler.util import error
from compiler.util import ir_pb2
from compiler.util import parser_types
from compiler.util import resources
_IrDebugInfo = collections.namedtuple("IrDebugInfo", ["ir", "debug_info",
"errors"])
class DebugInfo(object):
"""Debug information about Emboss parsing."""
__slots__ = ("modules")
def __init__(self):
self.modules = {}
def __eq__(self, other):
return self.modules == other.modules
def __ne__(self, other):
return not self == other
class ModuleDebugInfo(object):
"""Debug information about the parse of a single file.
Attributes:
file_name: The name of the file from which this module came.
tokens: The tokenization of this module's source text.
parse_tree: The raw parse tree for this module.
ir: The intermediate representation of this module, before additional
processing such as symbol resolution.
used_productions: The set of grammar productions used when parsing this
module.
source_code: The source text of the module.
"""
__slots__ = ("file_name", "tokens", "parse_tree", "ir", "used_productions",
"source_code")
def __init__(self, file_name):
self.file_name = file_name
self.tokens = None
self.parse_tree = None
self.ir = None
self.used_productions = None
self.source_code = None
def __eq__(self, other):
return (self.file_name == other.file_name and self.tokens == other.tokens
and self.parse_tree == other.parse_tree and self.ir == other.ir and
self.used_productions == other.used_productions and
self.source_code == other.source_code)
def __ne__(self, other):
return not self == other
def format_tokenization(self):
"""Renders self.tokens in a human-readable format."""
return "\n".join([str(token) for token in self.tokens])
def format_parse_tree(self, parse_tree=None, indent=""):
"""Renders self.parse_tree in a human-readable format."""
if parse_tree is None:
parse_tree = self.parse_tree
result = []
if isinstance(parse_tree, lr1.Reduction):
result.append(indent + parse_tree.symbol)
if parse_tree.children:
result.append(":\n")
for child in parse_tree.children:
result.append(self.format_parse_tree(child, indent + " "))
else:
result.append("\n")
else:
result.append("{}{}\n".format(indent, parse_tree))
return "".join(result)
def format_module_ir(self):
"""Renders self.ir in a human-readable format."""
return self.ir.to_json(indent=2)
def format_production_set(productions):
"""Renders a set of productions in a human-readable format."""
return "\n".join([str(production) for production in sorted(productions)])
_cached_modules = {}
def parse_module_text(source_code, file_name):
"""Parses the text of a module, returning a module-level IR.
Arguments:
source_code: The text of the module to parse.
file_name: The name of the module's source file (will be included in the
resulting IR).
Returns:
A module-level intermediate representation (IR), prior to import and symbol
resolution, and a corresponding ModuleDebugInfo, for debugging the parser.
Raises:
FrontEndFailure: An error occurred while parsing the module. str(error)
will give a human-readable error message.
"""
# This is strictly an optimization to speed up tests, mostly by avoiding the
# need to re-parse the prelude for every test .emb.
if (source_code, file_name) in _cached_modules:
debug_info = _cached_modules[source_code, file_name]
ir = ir_pb2.Module()
ir.CopyFrom(debug_info.ir)
else:
debug_info = ModuleDebugInfo(file_name)
debug_info.source_code = source_code
tokens, errors = tokenizer.tokenize(source_code, file_name)
if errors:
return _IrDebugInfo(None, debug_info, errors)
debug_info.tokens = tokens
parse_result = parser.parse_module(tokens)
if parse_result.error:
return _IrDebugInfo(
None,
debug_info,
[error.make_error_from_parse_error(file_name, parse_result.error)])
debug_info.parse_tree = parse_result.parse_tree
used_productions = set()
ir = module_ir.build_ir(parse_result.parse_tree, used_productions)
ir.source_text = source_code
debug_info.used_productions = used_productions
debug_info.ir = ir_pb2.Module()
debug_info.ir.CopyFrom(ir)
_cached_modules[source_code, file_name] = debug_info
ir.source_file_name = file_name
return _IrDebugInfo(ir, debug_info, [])
def parse_module(file_name, file_reader):
"""Parses a module, returning a module-level IR.
Arguments:
file_name: The name of the module's source file.
file_reader: A callable that returns either:
(file_contents, None) or
(None, list_of_error_detail_strings)
Returns:
(ir, debug_info, errors), where ir is a module-level intermediate
representation (IR), debug_info is a ModuleDebugInfo containing the
tokenization, parse tree, and original source text of all modules, and
errors is a list of tokenization or parse errors. If errors is not an empty
list, ir will be None.
Raises:
FrontEndFailure: An error occurred while reading or parsing the module.
str(error) will give a human-readable error message.
"""
source_code, errors = file_reader(file_name)
if errors:
location = parser_types.make_location((1, 1), (1, 1))
return None, None, [
[error.error(file_name, location, "Unable to read file.")] +
[error.note(file_name, location, e) for e in errors]
]
return parse_module_text(source_code, file_name)
def get_prelude():
"""Returns the module IR and debug info of the Emboss Prelude."""
return parse_module_text(
resources.load("compiler.front_end", "prelude.emb"), "")
def parse_emboss_file(file_name, file_reader, stop_before_step=None):
"""Fully parses an .emb, and returns an IR suitable for passing to a back end.
parse_emboss_file is a convenience function which calls only_parse_emboss_file
and process_ir.
Arguments:
file_name: The name of the module's source file.
file_reader: A callable that returns the contents of files, or raises
IOError.
stop_before_step: If set, parse_emboss_file will stop normalizing the IR
just before the specified step. This parameter should be None for
non-test code.
Returns:
(ir, debug_info, errors), where ir is a complete IR, ready for consumption
by an Emboss back end, debug_info is a DebugInfo containing the
tokenization, parse tree, and original source text of all modules, and
errors is a list of tokenization or parse errors. If errors is not an empty
list, ir will be None.
"""
ir, debug_info, errors = only_parse_emboss_file(file_name, file_reader)
if errors:
return _IrDebugInfo(None, debug_info, errors)
ir, errors = process_ir(ir, stop_before_step)
if errors:
return _IrDebugInfo(None, debug_info, errors)
return _IrDebugInfo(ir, debug_info, errors)
def only_parse_emboss_file(file_name, file_reader):
"""Parses an .emb, and returns an IR suitable for process_ir.
only_parse_emboss_file parses the given file and all of its transitive
imports, and returns a first-stage intermediate representation, which can be
passed to process_ir.
Arguments:
file_name: The name of the module's source file.
file_reader: A callable that returns the contents of files, or raises
IOError.
Returns:
(ir, debug_info, errors), where ir is an intermediate representation (IR),
debug_info is a DebugInfo containing the tokenization, parse tree, and
original source text of all modules, and errors is a list of tokenization or
parse errors. If errors is not an empty list, ir will be None.
"""
file_queue = [file_name]
files = {file_name}
debug_info = DebugInfo()
ir = ir_pb2.EmbossIr(module=[])
while file_queue:
file_to_parse = file_queue[0]
del file_queue[0]
if file_to_parse:
module, module_debug_info, errors = parse_module(file_to_parse,
file_reader)
else:
module, module_debug_info, errors = get_prelude()
if module_debug_info:
debug_info.modules[file_to_parse] = module_debug_info
if errors:
return _IrDebugInfo(None, debug_info, errors)
ir.module.extend([module]) # Proto supports extend but not append here.
for import_ in module.foreign_import:
if import_.file_name.text not in files:
file_queue.append(import_.file_name.text)
files.add(import_.file_name.text)
return _IrDebugInfo(ir, debug_info, [])
def process_ir(ir, stop_before_step):
"""Turns a first-stage IR into a fully-processed IR.
process_ir performs all of the semantic processing steps on `ir`: resolving
symbols, checking dependencies, adding type annotations, normalizing
attributes, etc. process_ir is generally meant to be called with the result
of parse_emboss_file(), but in theory could be called with a first-stage
intermediate representation (IR) from another source.
Arguments:
ir: The IR to process. This structure will be modified during processing.
stop_before_step: If set, process_ir will stop normalizing the IR just
before the specified step. This parameter should be None for non-test
code.
Returns:
(ir, errors), where ir is a complete IR, ready for consumption by an Emboss
back end, and errors is a list of compilation errors. If errors is not an
empty list, ir will be None.
"""
passes = (synthetics.desugar,
symbol_resolver.resolve_symbols,
dependency_checker.find_dependency_cycles,
dependency_checker.set_dependency_order,
symbol_resolver.resolve_field_references,
type_check.annotate_types,
type_check.check_types,
expression_bounds.compute_constants,
attribute_checker.normalize_and_verify,
constraints.check_constraints,
write_inference.set_write_methods)
assert stop_before_step in [None] + [f.__name__ for f in passes], (
"Bad value for stop_before_step.")
# Some parts of the IR are synthesized from "natural" parts of the IR, before
# the natural parts have been fully error checked. Because of this, the
# synthesized parts can have errors; in a couple of cases, they can have
# errors that show up in an earlier pass than the errors in the natural parts
# of the IR. As an example:
#
# struct Foo:
# 0 [+1] bits:
# 0 [+1] Flag flag
# 1 [+flag] UInt:8 field
#
# In this case, the use of `flag` as the size of `field` is incorrect, because
# `flag` is a boolean, but the size of a field must be an integer.
#
# Type checking occurs in two passes: in the first pass, expressions are
# checked for internal consistency. In the second pass, expression types are
# checked against their location. The use of `flag` would be caught in the
# second pass.
#
# However, the generated_fields pass will synthesize a $size_in_bytes virtual
# field that would look like:
#
# struct Foo:
# 0 [+1] bits:
# 0 [+1] Flag flag
# 1 [+flag] UInt:8 field
# let $size_in_bytes = $max(true ? 0 + 1 : 0, true ? 1 + flag : 0)
#
# Since `1 + flag` is not internally consistent, this type error would be
# caught in the first pass, and the user would see a very strange error
# message that "the right-hand argument of operator `+` must be an integer."
#
# In order to avoid showing these kinds of errors to the user, we defer any
# errors in synthetic parts of the IR. Unless there is a compiler bug, those
# errors will show up as errors in the natural parts of the IR, which should
# be much more comprehensible to end users.
#
# If, for some reason, there is an error in the synthetic IR, but no error in
# the natural IR, the synthetic errors will be shown. In this case, the
# formatting for the synthetic errors will show '[compiler bug]' for the
# error location, which (hopefully) will provide the end user with a cue that
# the error is a compiler bug.
deferred_errors = []
for function in passes:
if stop_before_step == function.__name__:
return (ir, [])
errors, hidden_errors = error.split_errors(function(ir))
if errors:
return (None, errors)
deferred_errors.extend(hidden_errors)
if deferred_errors:
return (None, deferred_errors)
assert stop_before_step is None, "Bad value for stop_before_step."
return (ir, [])