ogParser.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-


"""
    OpenGEODE SDL92 parser

    This library builds the SDL AST (described in ogAST.py)
    The AST can then be used to build SDL backends such as the
    diagram editor (placing symbols in a graphical canvas for editition)
    or code generators, etc.

    The AST build is based on the ANTLR-grammar and generated lexer and parser
    (the grammar is in the file sdl92.g and requires antlr 3.1.3 for Python
    to be compiled and used).

    During the build of the AST this library makes a number of semantic
    checks on the SDL input mode.

    Copyright (c) 2012-2013 European Space Agency

    Designed and implemented by Maxime Perrotin

    Contact: maxime.perrotin@esa.int
"""

__author__ = 'Maxime Perrotin'

import sys
import os
import math
import logging
import traceback
from itertools import chain, permutations, combinations
from collections import defaultdict, Counter
import antlr3
import antlr3.tree

import sdl92Lexer as lexer
from sdl92Parser import sdl92Parser

import samnmax
import ogAST
from Asn1scc import parse_asn1, ASN1

LOG = logging.getLogger(__name__)

EXPR_NODE = {
    lexer.PLUS: ogAST.ExprPlus,
    lexer.ASTERISK: ogAST.ExprMul,
    lexer.IMPLIES: ogAST.ExprImplies,
    lexer.DASH: ogAST.ExprMinus,
    lexer.OR: ogAST.ExprOr,
    lexer.AND: ogAST.ExprAnd,
    lexer.XOR: ogAST.ExprXor,
    lexer.EQ: ogAST.ExprEq,
    lexer.NEQ: ogAST.ExprNeq,
    lexer.GT: ogAST.ExprGt,
    lexer.GE: ogAST.ExprGe,
    lexer.LT: ogAST.ExprLt,
    lexer.LE: ogAST.ExprLe,
    lexer.DIV: ogAST.ExprDiv,
    lexer.MOD: ogAST.ExprMod,
    lexer.APPEND: ogAST.ExprAppend,
    lexer.IN: ogAST.ExprIn,
    lexer.REM: ogAST.ExprRem,
    lexer.NOT: ogAST.ExprNot,
    lexer.NEG: ogAST.ExprNeg,
    lexer.PRIMARY: ogAST.Primary,
}

# Insert current path in the search list for importing modules
sys.path.insert(0, '.')

DV = None

# Code generator backends may need some intemediate variables to process
# expressions. For convenience and to avoid multiple pass parsing, the parser
# tries to guess where they may be useful, and adds a hint in the AST.
TMPVAR = 0

# ASN.1 types used to support the signature of special operators
INTEGER = type('IntegerType', (object,), {'kind': 'IntegerType',
                                          'Min': str(-(2 ** 63)),
                                          'Max': str(2 ** 63 - 1)})
INT32 = type('Integer32Type', (object,), {'kind': 'Integer32Type',
                                          'Min': '-2147483648',
                                          'Max': '2147483647'})
NUMERICAL = type('NumericalType', (object,), {'kind': 'Numerical'})
TIMER = type('TimerType', (object,), {'kind': 'TimerType'})
REAL = type('RealType', (object,), {'kind': 'RealType',
                                    'Min': str(1e-308),
                                    'Max': str(1e308)})
LIST = type('ListType', (object,), {'kind': 'ListType'})
ANY_TYPE = type('AnyType', (object,), {'kind': 'AnyType'})
CHOICE = type('ChoiceType', (object,), {'kind': 'ChoiceType'})
BOOLEAN = type('BooleanType', (object,), {'kind': 'BooleanType'})
RAWSTRING = type('RawString', (object,), {'kind': 'StandardStringType',
                                          'Min': '0', 'Max': '255'})
OCTETSTRING = type('OctetString', (object,), {'kind': 'OctetStringType'})
ENUMERATED = type('EnumeratedType', (object,), {'kind': 'EnumeratedType'})

UNKNOWN_TYPE = type('UnknownType', (object,), {'kind': 'UnknownType'})

SPECIAL_OPERATORS = {
    'abs': [{'type': NUMERICAL, 'direction': 'in'}],
    'ceil': [{'type': REAL, 'direction': 'in'}],
    'cos': [{'type': REAL, 'direction': 'in'}],
    'fix': [{'type': NUMERICAL, 'direction': 'in'}],
    'float': [{'type': NUMERICAL, 'direction': 'in'}],
    'floor': [{'type': REAL, 'direction': 'in'}],
    'length': [{'type': LIST, 'direction': 'in'}],
    'num': [{'type': ENUMERATED, 'direction': 'in'}],
    'power': [
        {'type': NUMERICAL, 'direction': 'in'},
        {'type': INTEGER, 'direction': 'in'}
    ],
    'present': [{'type': CHOICE, 'direction': 'in'}],
    'reset_timer': [{'type': TIMER, 'direction': 'in'}],
    'round': [{'type': REAL, 'direction': 'in'}],
    'set_timer': [
        {'type': INTEGER, 'direction': 'in'},
        {'type': TIMER, 'direction': 'in'}
    ],
    'sin': [{'type': REAL, 'direction': 'in'}],
    'sqrt': [{'type': REAL, 'direction': 'in'}],
    'trunc': [{'type': REAL, 'direction': 'in'}],
    'write': [{'type': ANY_TYPE, 'direction': 'in'}],
    'writeln': [{'type': ANY_TYPE, 'direction': 'in'}],
}

# Container to keep a list of types mapped from ANTLR Tokens
# (Used with singledispatch/visitor pattern)
ANTLR_TOKEN_TYPES = {a: type(a, (antlr3.tree.CommonTree,), {})
                    for a, b in lexer.__dict__.viewitems() if type(b) == int}


# Shortcut to create a new referenced ASN.1 type
new_ref_type = lambda refname: \
        type(str(refname), (object,),
                {'kind': 'ReferenceType',
                 'ReferencedTypeName': refname.replace('_', '-')})

# Shortcut to return a type name (Reference name or basic type)
type_name = lambda t: \
                t.kind if t.kind != 'ReferenceType' else t.ReferencedTypeName

types = lambda: getattr(DV, 'types', {})


def set_global_DV(asn1_filenames):
    ''' Call ASN.1 parser and set the global dataview AST entry (DV) '''
    global DV
    try:
        DV = parse_asn1(tuple(asn1_filenames),
                        ast_version=ASN1.UniqueEnumeratedNames,
                        flags=[ASN1.AstOnly])
    except (ImportError, NameError) as err:
        # Can happen if DataView.py is not there
        LOG.error('Error loading ASN.1 model')
        LOG.debug(str(err))
    except TypeError as err:
        LOG.debug(traceback.format_exc())
        raise TypeError('ASN.1 compiler failed - {}'.format(str(err)))


def substring_range(substring):
    ''' Return the range of a substring '''
    left, right = substring.value[1]['substring']
    left_bty = find_basic_type(left.exprType)
    right_bty = find_basic_type(right.exprType)
    return left_bty.Min, right_bty.Max


def is_integer(ty):
    ''' Return true if a type is an Integer Type '''
    return find_basic_type(ty).kind in (
        'IntegerType',
        'Integer32Type'
    )


def is_real(ty):
    ''' Return true if a type is a Real Type '''
    return find_basic_type(ty).kind == 'RealType'


def is_numeric(ty):
    ''' Return true if a type is a Numeric Type '''
    return find_basic_type(ty).kind in (
        'IntegerType',
        'Integer32Type',
        'Numerical',
        'RealType'
    )


def is_boolean(ty):
    ''' Return true if a type is a Boolean Type '''
    return find_basic_type(ty).kind == 'BooleanType'


def is_string(ty):
    ''' Return true if a type is a String Type '''
    return find_basic_type(ty).kind in (
        'StandardStringType',
        'OctetStringType',
        'StringType'
    )


def is_sequenceof(ty):
    ''' Return true if a type is a SequenceOf Type '''
    return find_basic_type(ty).kind == 'SequenceOfType'


def is_list(ty):
    ''' Return true if a type is a List Type '''
    return is_string(ty) or is_sequenceof(ty) or ty == LIST


def is_enumerated(ty):
    ''' Return true if a type is an Enumerated Type '''
    return find_basic_type(ty).kind == 'EnumeratedType' or ty == ENUMERATED


def is_sequence(ty):
    ''' Return true if a type is a Sequence Type '''
    return find_basic_type(ty).kind == 'SequenceType'


def is_choice(ty):
    ''' Return true if a type is a Choice Type '''
    return find_basic_type(ty).kind == 'ChoiceType' or ty == CHOICE


def is_timer(ty):
    ''' Return true if a type is a Timer Type '''
    return find_basic_type(ty).kind == 'TimerType'


def sdl_to_asn1(sort):
    '''
        Convert case insensitive type reference to the actual type as found
        in the ASN.1 datamodel
    '''
    for asn1_type in types().viewkeys():
        if sort.replace('_', '-').lower() == asn1_type.lower():
            break
    else:
        raise TypeError('Type {} not found in ASN.1 model'.format(sort))
    return new_ref_type(asn1_type)


def node_filename(node):
    ''' Return the filename associated to the stream of this node '''
    parent = node
    while parent:
        try:
            return parent.getToken().getInputStream().fileName
        except AttributeError:
            parent = parent.getParent()
    return None


def token_stream(node):
    '''
        Return the token stream associated to a tree node
        It is set at the root of the tree by the parser
    '''
    parent = node
    while parent:
        try:
            return parent.token_stream
        except AttributeError:
            parent = parent.getParent()


def signals_in_system(ast):
    ''' Recursively find signal definitions in a nested SDL model '''
    all_signals = []
    for block in ast.blocks:
        all_signals.extend(signals_in_system(block))
    all_signals.extend(ast.signals)
    return all_signals


def find_process_declaration(ast, process_name):
    ''' Recursively search for a process declaration in a nested SDL model '''
    for block in ast.blocks:
        result = find_process_declaration(block, process_name)
        if result:
            return result
    try:
        for process in ast.processes:
            if process.processName == process_name:
                return process
    except AttributeError:
        return None
    return None


def valid_output(scope):
    '''
        Yields the output, procedures, and operators names,
        that is all the elements that can be valid in an OUTPUT symbol
        (does not mean it IS valid - caller still has to check it)
    '''
    for out_sig in scope.output_signals:
        yield out_sig['name'].lower()
    for proc in scope.procedures:
        yield proc.inputString.lower()
    for special_op in SPECIAL_OPERATORS:
        yield special_op.lower()


def get_interfaces(ast, process_name):
    '''
        Search for the list of input and output signals (async PI/RI)
        and procedures (sync RI) of a process in a given top-level AST
    '''
    all_signals, async_signals, errors = [], [], []
    system = None

    # Move up to the system level, in case process is nested in a block
    # and not defined at root level as it is the case when it is referenced
    system = ast
    while hasattr(system, 'parent'):
        system = system.parent

    # If we are at AST level, check in all systems, otherwise in current one
    iterator = ast.systems if hasattr(ast, 'systems') else (system,)

    for system in iterator:
        all_signals.extend(signals_in_system(system))
        process_ref = find_process_declaration(system, process_name)
        if process_ref:
            # Go to the block where the process is defined
            process_parent = process_ref.parent
            break
    else:
        if isinstance(ast, ogAST.Block):
            process_parent = ast
        else:
            raise TypeError('Process ' + process_name +
                        ' is defined but not declared in a system')
    # Find in and out signals names using the signalroutes
    undeclared_signals = []
    for each in process_parent.signalroutes:
        for route in each['routes']:
            if route['source'] == process_name:
                direction = 'out'
            elif route['dest'] == process_name:
                direction = 'in'
            else:
                continue
            for sig_id in route['signals']:
                # Copy the signal to the result dict
                try:
                    found, = [dict(sig) for sig in all_signals
                              if sig['name'].lower() == sig_id.lower()]
                    found['direction'] = direction
                    async_signals.append(found)
                except ValueError:
                    undeclared_signals.append(sig_id)
    if undeclared_signals:
        errors = ['Missing declaration for signal(s) {}'
                  .format(', '.join(undeclared_signals))]
    return async_signals, system.procedures, errors


def get_input_string(root):
    ''' Return the input string of a tree node '''
    return token_stream(root).toString(root.getTokenStartIndex(),
            root.getTokenStopIndex())


def error(root, msg):
    ''' Return an error message '''
    return '{} - "{}"'.format(msg, get_input_string(root))


def warning(root, msg):
    ''' Return a warning message '''
    return '{} - "{}"'.format(msg, get_input_string(root))


def tmp():
    ''' Return a temporary variable name '''
    global TMPVAR
    varname = TMPVAR
    TMPVAR += 1
    return varname


def get_state_list(process_root):
    ''' Return the list of states of a process '''
    # 1) get all STATE statements
    states = (child for child in process_root.getChildren()
            if child.type == lexer.STATE)
    # 2) keep only the ones containing a STATELIST token (i.e. no ASTERISK)
    relevant = (child for state in states for child in state.getChildren()
            if child.type == lexer.STATELIST)
    # 3) extract the state list from each of them
    state_list = [s.text.lower() for r in relevant for s in r.getChildren()]
    # state_list.append('START')
    # 4) create a set to remove duplicates
    return set(state_list)


def find_basic_type(a_type, pool=None):
    ''' Return the ASN.1 basic type of a_type '''
    basic_type = a_type or UNKNOWN_TYPE
    pool = pool or types()
    while basic_type.kind == 'ReferenceType':
        # Find type with proper case in the data view
        for typename in pool.viewkeys():
            if typename.lower() == basic_type.ReferencedTypeName.lower():
                basic_type = pool[typename].type
                break
        else:
            raise TypeError('Type "' + type_name(basic_type) +
                            '" was not found in Dataview')
    return basic_type


def signature(name, context):
    ''' Return the signature of a procecure/output/operator '''
    name = name.lower()
    if name in SPECIAL_OPERATORS:
        return SPECIAL_OPERATORS[name]

    for out_sig in context.output_signals:
        if out_sig['name'].lower() == name:
            signature = []
            if out_sig.get('type'):
                # output signals: one single parameter
                signature.append({
                    'type': out_sig.get('type'),
                    'name': out_sig.get('param_name' or ''),
                    'direction': 'in',
                })
            return signature

    for inner_proc in context.procedures:
        proc_name = inner_proc.inputString
        if proc_name.lower() == name:
            return inner_proc.fpar

    raise AttributeError('Operator/output/procedure not found: ' + name)


def check_call(name, params, context):
    ''' Check the parameter types of a procedure/output/operator call,
        returning the type of its result '''
    LOG.debug('[check_call] ' + name + ' - ' + str(params))

    # Special case for write/writeln functions
    if name.lower() in ('write', 'writeln'):
        for p in params:
            p_ty = p.exprType
            if is_numeric(p_ty) or is_boolean(p_ty) or is_string(p_ty):
                continue
            raise TypeError('Type {} not supported in call to {}'.
                format(type_name(p.exprType), name))
        return

    # (1) Find the signature of the function
    # signature will hold the list of parameters for the function
    sign = signature(name, context)

    # (2) Check that the number of given parameters matches the signature
    if len(sign) != len(params):
        raise TypeError('Expected {} arguments in call to {} ({} received)'.
            format(len(sign), name, len(params)))

    # (3) Check each individual parameter type
    for idx, param in enumerate(params):
        expr = ogAST.ExprAssign()
        expr.left = ogAST.PrimVariable()
        expr.left.exprType = sign[idx]['type']
        expr.right = param

        try:
            fix_expression_types(expr, context)
            params[idx] = expr.right
        except TypeError:
            expected = type_name(sign[idx]['type'])
            received = type_name(expr.right.exprType)
            raise TypeError('Expected type {} in call to {} ({} received)'.
                format(expected, name, received))

        if sign[idx].get('direction') != 'in' \
                and not isinstance(expr.right, ogAST.PrimVariable):
            raise TypeError('OUT parameter "{}" is not a variable'
                .format(expr.right.inputString))

    # (4) Compute the type of the result
    param_btys = [find_basic_type(p.exprType) for p in params]
    if name == 'abs':
        return type('Abs', (param_btys[0],), {
            'Min': str(max(float(param_btys[0].Min), 0)),
            'Max': str(max(float(param_btys[0].Max), 0))
        })

    elif name == 'ceil':
        return type('Ceil', (REAL,), {
            'Min': str(math.ceil(float(param_btys[0].Min))),
            'Max': str(math.ceil(float(param_btys[0].Max)))
        })

    elif name == 'cos':
        return type('Cos', (REAL,), {
            'Min': str(-1.0),
            'Max': str(1.0)
        })

    elif name == 'fix':
        return type('Fix', (INTEGER,), {
            'Min': param_btys[0].Min,
            'Max': param_btys[0].Max
        })

    elif name == 'float':
        return type('Float', (REAL,), {
            'Min': param_btys[0].Min,
            'Max': param_btys[0].Max
        })

    elif name == 'floor':
        return type('Floor', (REAL,), {
            'Min': str(math.floor(float(param_btys[0].Min))),
            'Max': str(math.floor(float(param_btys[0].Max)))
        })

    elif name == 'length':
        return type('Length', (INTEGER,), {
            'Min': param_btys[0].Min,
            'Max': param_btys[0].Max
        })

    elif name == 'num':
        enum_values = [int(each.IntValue)
                       for each in param_btys[0].EnumValues.viewvalues()]

        return type('Num', (INTEGER,), {
            'Min': str(min(enum_values)),
            'Max': str(max(enum_values))
        })

    elif name == 'power':
        return type('Power', (param_btys[0],), {
            'Min': str(pow(float(param_btys[0].Min),
                           float(param_btys[1].Min))),
            'Max': str(pow(float(param_btys[0].Max),
                           float(param_btys[1].Max)))
        })

    elif name == 'present':
        return type('Present', (object,), {
            'kind': 'ChoiceEnumeratedType',
            'EnumValues': param_btys[0].Children
        })

    elif name == 'round':
        return type('Round', (REAL,), {
            'Min': str(round(float(param_btys[0].Min))),
            'Max': str(round(float(param_btys[0].Max)))
        })

    elif name == 'sin':
        return type('Sin', (REAL,), {
            'Min': str(-1.0),
            'Max': str(1.0)
        })

    elif name == 'sqrt':
        return type('Sqrt', (REAL,), {
            'Min': str(0.0),
            'Max': str(math.sqrt(float(param_btys[0].Max)))
        })

    elif name == 'trunc':
        return type('Trunc', (REAL,), {
            'Min': str(math.trunc(float(param_btys[0].Min))),
            'Max': str(math.trunc(float(param_btys[0].Max)))
        })

    return UNKNOWN_TYPE


def check_range(typeref, type_to_check):
    ''' Verify the that the Min/Max bounds of two types are compatible
        Called to test that assignments are withing allowed range
        both types assumed to be basic types
    '''
    try:
        if float(type_to_check.Min) < float(typeref.Min) \
                or float(type_to_check.Max) > float(typeref.Max):
            raise TypeError('Expression evaluation in range [{}..{}], '
                            'outside expected range [{}..{}]'
                    .format(type_to_check.Min, type_to_check.Max,
                            typeref.Min, typeref.Max))
    except (AttributeError, ValueError):
        raise TypeError('Missing range')


def check_type_compatibility(primary, type_ref, context):
    '''
        Check if an ogAST.Primary (raw value, enumerated, ASN.1 Value...)
        is compatible with a given type (type_ref is an ASN1Scc type)
        Does not return anything if OK, otherwise raises TypeError
    '''
    assert type_ref is not None
    if type_ref is UNKNOWN_TYPE:
        #print traceback.print_stack()
        raise TypeError('Type reference is unknown')

    basic_type = find_basic_type(type_ref)
    LOG.debug("[check_type_compatibility] "
              "checking if {value} is of type {typeref}"
              .format(value=primary.inputString, typeref=type_name(type_ref)))

    if (isinstance(primary, ogAST.PrimEnumeratedValue)
            and basic_type.kind.endswith('EnumeratedType')):
        # If type ref is an enumeration, check that the value is valid
        # Note, when using the "present" operator of a CHOICE type, the
        # resulting value is actually an EnumeratedType
        enumerant = primary.inputString.replace('_', '-').lower()
        for each in basic_type.EnumValues.keys():
            if each.lower() == enumerant:
                # Found -> all OK
                return
        else:
            err = ('Value "' + primary.inputString +
                   '" not in this enumeration: ' +
                   str(basic_type.EnumValues.keys()))
            raise TypeError(err)
    elif isinstance(primary, ogAST.PrimConditional):
        then_expr = primary.value['then']
        else_expr = primary.value['else']

        for expr in (then_expr, else_expr):
            if expr.is_raw:
                check_type_compatibility(expr, type_ref, context)
        return

    elif isinstance(primary, ogAST.PrimVariable):
        try:
            compare_types(primary.exprType, type_ref)
        except TypeError as err:
            raise TypeError('{expr} should be of type {ty} - {err}'
                            .format(expr=primary.inputString,
                                    ty=type_name(type_ref),
                                    err=str(err)))
        return

    elif isinstance(primary, ogAST.PrimInteger) \
            and (is_integer(type_ref) or type_ref == NUMERICAL):
        return

    elif isinstance(primary, ogAST.PrimReal) \
            and (is_real(type_ref) or type_ref == NUMERICAL):
        return

    elif isinstance(primary, ogAST.PrimBoolean) and is_boolean(type_ref):
        return

    elif (isinstance(primary, ogAST.PrimEmptyString) and
                                         basic_type.kind == 'SequenceOfType'):
        if int(basic_type.Min) == 0:
            return
        else:
            raise TypeError('SEQUENCE OF has a minimum size of '
                            + basic_type.Min + ')')
    elif isinstance(primary, ogAST.PrimSequenceOf) \
            and basic_type.kind == 'SequenceOfType':
        if type_ref.__name__ != 'Apnd' and \
                (len(primary.value) < int(basic_type.Min) or
                len(primary.value) > int(basic_type.Max)):
            raise TypeError(str(len(primary.value)) +
                      ' elements in SEQUENCE OF, while constraint is [' +
                      str(basic_type.Min) + '..' + str(basic_type.Max) + ']')
        for elem in primary.value:
            check_type_compatibility(elem, basic_type.type, context)
        return
    elif isinstance(primary, ogAST.PrimSequence) \
            and basic_type.kind == 'SequenceType':
        user_nb_elem = len(primary.value.keys())
        type_nb_elem = len(basic_type.Children.keys())
        optional_fields = [field.lower().replace('-', '_')
                           for field, val in basic_type.Children.viewitems()
                           if val.Optional == 'True']
        user_fields = [field.lower() for field in primary.value.keys()]
#       if user_nb_elem != type_nb_elem:
#           raise TypeError('Wrong number of fields in SEQUENCE of type {}'
#                           .format(type_name(type_ref)))
#       else:
        for field, fd_data in basic_type.Children.viewitems():
            ufield = field.replace('-', '_')
            if ufield.lower() not in optional_fields \
                    and ufield.lower() not in user_fields:
                raise TypeError('Missing mandatory field {field} in SEQUENCE'
                                ' of type {t1} '
                                .format(field=ufield,
                                        t1=type_name(type_ref)))
            elif field.lower() not in user_fields:
                # Optional field not set - OK
                continue
            else:
                # If the user field is a raw value
                if primary.value[ufield].is_raw:
                    check_type_compatibility(primary.value[ufield],
                                             fd_data.type, context)
                else:
                    # Compare the types for semantic equivalence
                    try:
                        compare_types(
                            primary.value[ufield].exprType, fd_data.type)
                    except TypeError as err:
                        raise TypeError('Field ' + ufield +
                                    ' is not of the proper type, i.e. ' +
                                    type_name(fd_data.type) +
                                    ' - ' + str(err))
        return
    elif isinstance(primary, ogAST.PrimChoiceItem) \
                              and basic_type.kind.startswith('Choice'):
        for choicekey, choice in basic_type.Children.viewitems():
            if choicekey.lower().replace('-', '_') == \
                    primary.value['choice'].lower().replace('-', '_'):
                break
        else:
            raise TypeError('Non-existent choice "{choice}" in type {t1}'
                            .format(choice=primary.value['choice'],
                            t1=type_name(type_ref)))
        # compare primary.value['value']
        # with basic_type['Children'][primary.choiceItem['choice']]
        value = primary.value['value']
        choice_field_type = choice.type
        # if the user field is a raw value:
        if value.is_raw:
            check_type_compatibility(value, choice_field_type, context)
        # Compare the types for semantic equivalence:
        else:
            try:
                compare_types(value.exprType, choice_field_type)
            except TypeError as err:
                raise TypeError(
                            'Field {field} in CHOICE is not of type {t1} - {e}'
                            .format(field=primary.value['choice'],
                                    t1=type_name(choice_field_type),
                                    e=str(err)))
        value.exprType = choice_field_type         # XXX
        return
    elif isinstance(primary, ogAST.PrimChoiceDeterminant) \
                and basic_type.kind.startswith('Choice'):
        for choicekey, choice in basic_type.EnumValues.viewitems():
            if choicekey.replace('-', '_').lower() == \
                    primary.inputString.lower():
                break
        else:
            raise TypeError('Non-existent choice "{choice}" in type {t1}'
                            .format(choice=primary.inputString,
                            t1=type_name(type_ref)))

    elif isinstance(primary, ogAST.PrimStringLiteral):
        # Octet strings
        basic_type = find_basic_type(type_ref)
        if basic_type.kind == 'StandardStringType':
            return
        elif basic_type.kind.endswith('StringType'):
            if int(basic_type.Min) <= len(
                    primary.value[1:-1]) <= int(basic_type.Max):
                return
            else:
                raise TypeError('Invalid string literal - check that length is'
                                'within the bound limits {Min}..{Max}'.format
                            (Min=str(basic_type.Min), Max=str(basic_type.Max)))
        else:
            raise TypeError('String literal not expected')
    elif (isinstance(primary, ogAST.PrimMantissaBaseExp) and
                                            basic_type.kind == 'RealType'):
        LOG.debug('PROBABLY (it is a float but I did not check'
                  'if values are compatible)')
        return
    else:
        raise TypeError('{prim} does not match type {t1}'
                        .format(prim=primary.inputString,
                                t1=type_name(type_ref)))


def compare_types(type_a, type_b):
    '''
       Compare two types, return if they are semantically equivalent,
       otherwise raise TypeError
    '''
    LOG.debug('[compare_types]' + str(type_a) + ' and ' + str(type_b) + ': ')

    type_a = find_basic_type(type_a)
    type_b = find_basic_type(type_b)

    if type_a == type_b:
        return
    elif NUMERICAL in (type_a, type_b) and is_numeric(type_a) \
            and is_numeric(type_b):
        return
    elif LIST in (type_a, type_b) and is_list(type_a) and is_list(type_b):
        return
    elif ENUMERATED in (type_a, type_b) and is_enumerated(type_a) \
            and is_enumerated(type_b):
        return
    elif CHOICE in (type_a, type_b) and is_choice(type_a) and is_choice(type_b):
        return

    # Check if both types have basic compatibility

    if type_a.kind == type_b.kind:
        if type_a.kind == 'SequenceOfType':
            if type_a.Min == type_a.Max:
                if type_a.Min == type_b.Min == type_b.Max:
                    compare_types(type_a.type, type_b.type)
                    return
                else:
                    raise TypeError('Incompatible sizes - size of {} can vary'
                                    .format(type_name(type_b)))
            elif(int(type_b.Min) >= int(type_a.Min)
                 and int(type_b.Max) <= int(type_a.Max)):
                compare_types(type_a.type, type_b.type)
                return
            else:
                compare_types(type_a.type, type_b.type)
                raise Warning('Size constraints mismatch - risk of overflow')
        # TODO: Check that OctetString types have compatible range
        return
    elif is_string(type_a) and is_string(type_b):
        return
    elif is_integer(type_a) and is_integer(type_b):
        return
    elif is_real(type_a) and is_real(type_b):
        return
    else:
        raise TypeError('Incompatible types {} and {}'.format(
            type_name(type_a),
            type_name(type_b)
        ))


def find_variable_type(var, context):
    ''' Look for a variable name in the context and return its type '''
    LOG.debug('[find_variable] checking if ' + str(var) + ' is defined')

    # all DCL-variables
    all_visible_variables = dict(context.global_variables)
    all_visible_variables.update(context.variables)

    # First check locally, i.e. in FPAR
    try:
        for variable in context.fpar:
            if variable['name'].lower() == var.lower():
                return variable['type']
    except AttributeError:
        # No FPAR section
        pass

    for varname, (vartype, _) in all_visible_variables.viewitems():
        # Case insensitive comparison with variables
        if var.lower() == varname.lower():
            return vartype

    for timer in chain(context.timers, context.global_timers):
        if var.lower() == timer.lower():
            return TIMER

    # check if is a ASN.1 constant
    for varname, vartype in DV.variables.viewitems():
        if var.lower() == varname.lower().replace('-', '_'):
            return vartype.type

    LOG.debug('[find_variable] result: not found, raising exception')
    raise AttributeError('Variable {var} not defined'.format(var=var))


def fix_enumerated_and_choice(expr_enum, context):
    ''' If left side of the expression is of Enumerated or Choice type,
        check if right side is a literal of that sort, and update type '''
    kind = find_basic_type(expr_enum.left.exprType).kind
    if kind == 'EnumeratedType':
        prim = ogAST.PrimEnumeratedValue(primary=expr_enum.right)
    elif kind == 'ChoiceEnumeratedType':
        prim = ogAST.PrimChoiceDeterminant(primary=expr_enum.right)
    try:
        check_type_compatibility(prim, expr_enum.left.exprType, context)
        expr_enum.right = prim
        expr_enum.right.exprType = expr_enum.left.exprType
    except (UnboundLocalError, AttributeError, TypeError):
        pass
    else:
        LOG.debug('Fixed enumerated/choice: {}'.format(expr_enum.inputString))


def fix_expression_types(expr, context):
    ''' Check/ensure type consistency in binary expressions '''
    for _ in range(2):
        # Check if an raw enumerated value is of a reference type
        fix_enumerated_and_choice(expr, context)
        expr.right, expr.left = expr.left, expr.right

    for side in (expr.right, expr.left):
        if side.is_raw:
            raw_expr = side
        else:
            typed_expr = side
            ref_type = typed_expr.exprType

    # If a side is a raw Sequence Of with unknown type, try to resolve it
    for side_a, side_b in permutations(('left', 'right')):
        value = getattr(expr, side_a)  # get expr.left then expr.right
        if not isinstance(value, ogAST.PrimSequenceOf):
            continue
        other = getattr(expr, side_b)  # other side
        basic = find_basic_type(value.exprType)
        if basic.kind == 'SequenceOfType' and basic.type == UNKNOWN_TYPE:
            asn_type = find_basic_type(other.exprType)
            if asn_type.kind == 'SequenceOfType':
                asn_type = asn_type.type
                for idx, elem in enumerate(value.value):
                    check_expr = ogAST.ExprAssign()
                    check_expr.left = ogAST.PrimVariable()
                    check_expr.left.exprType = asn_type
                    check_expr.right = elem
                    fix_expression_types(check_expr, context)
                    value.value[idx] = check_expr.right
            # the type of the raw PrimSequenceOf can be set now
            value.exprType.type = asn_type

    if isinstance(expr, ogAST.ExprIn):
        return

    if not expr.right.is_raw and not expr.left.is_raw:
        unknown = [uk_expr for uk_expr in expr.right, expr.left
                   if uk_expr.exprType == UNKNOWN_TYPE]
        if unknown:
            #print traceback.print_stack()
            raise TypeError('Cannot resolve type of "{}"'
                            .format(unknown[0].inputString))

    # In Sequence, Choice and SEQUENCE OF expressions,
    # we must fix missing inner types
    # (due to similarities, the following should be refactored FIXME)
    if isinstance(expr.right, ogAST.PrimSequence):
        # left side must have a known type
        asn_type = find_basic_type(expr.left.exprType)
        if asn_type.kind != 'SequenceType':
            raise TypeError('left side must be a SEQUENCE type')
        for field, fd_expr in expr.right.value.viewitems():
            if fd_expr.exprType == UNKNOWN_TYPE:
                try:
                    expected_type = asn_type.Children.get(
                            field.replace('_', '-')).type
                except AttributeError:
                    raise TypeError('Field not found: ' + field)
                check_expr = ogAST.ExprAssign()
                check_expr.left = ogAST.PrimVariable()
                check_expr.left.exprType = expected_type
                check_expr.right = fd_expr
                fix_expression_types(check_expr, context)
                # Id of fd_expr may have changed (enumerated, choice)
                expr.right.value[field] = check_expr.right
    elif isinstance(expr.right, ogAST.PrimChoiceItem):
        asn_type = find_basic_type(expr.left.exprType)
        field = expr.right.value['choice'].replace('_', '-')
        if asn_type.kind != 'ChoiceType' \
                or field.lower() not in [key.lower()
                                  for key in asn_type.Children.viewkeys()]:
            raise TypeError('Field is not valid in CHOICE:' + field)
        key, = [key for key in asn_type.Children.viewkeys()
                if key.lower() == field.lower()]
        if expr.right.value['value'].exprType == UNKNOWN_TYPE:
            try:
                expected_type = asn_type.Children.get(key).type
            except AttributeError:
                raise TypeError('Field not found in CHOICE: ' + field)
            check_expr = ogAST.ExprAssign()
            check_expr.left = ogAST.PrimVariable()
            check_expr.left.exprType = expected_type
            check_expr.right = expr.right.value['value']
            fix_expression_types(check_expr, context)
            expr.right.value['value'] = check_expr.right
    elif isinstance(expr.right, ogAST.PrimConditional):
        for det in ('then', 'else'):
            # Recursively fix possibly missing types in the expression
            check_expr = ogAST.ExprAssign()
            check_expr.left = ogAST.PrimVariable()
            check_expr.left.exprType = expr.left.exprType
            check_expr.right = expr.right.value[det]
            fix_expression_types(check_expr, context)
            expr.right.value[det] = check_expr.right

    if expr.right.is_raw != expr.left.is_raw:
        check_type_compatibility(raw_expr, ref_type, context)