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 re
import fnmatch
import logging
import traceback
from itertools import chain, permutations
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,
    lexer.IFTHENELSE: ogAST.PrimIfThenElse,
}

# 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'})
OCTETSTRING = type('OctetString', (object,), {'kind': 'OctetStringType'})

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


# Special SDL operators and signature
SPECIAL_OPERATORS = {'length': [LIST],
                     'write': [ANY_TYPE],
                     'writeln': [ANY_TYPE],
                     'present': [CHOICE],
                     'set_timer': [INTEGER, TIMER],
                     'reset_timer': [TIMER],
                     'abs': [NUMERICAL],
                     'float': [NUMERICAL],
                     'fix': [NUMERICAL],
                     'power': [NUMERICAL, INTEGER]}

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


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


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 = []
    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 not declared in a system')
    # Find in and out signals names using the signalroutes
    for signalroute in process_parent.signalroutes:
        for route in signalroute['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
                found, = [dict(sig) for sig in all_signals
                          if sig['name'] == sig_id]
                found['direction'] = direction
                async_signals.append(found)
    return async_signals, system.procedures


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):
    ''' Return the ASN.1 basic type of a_type '''
    basic_type = a_type or UNKNOWN_TYPE
    while basic_type.kind == 'ReferenceType':
        # Find type with proper case in the data view
        for typename in types().viewkeys():
            if typename.lower() == basic_type.ReferencedTypeName.lower():
                basic_type = types()[typename].type
                break
        else:
            raise TypeError('Type "' + type_name(basic_type) +
                            '" was not found in Dataview')
    return basic_type


def is_constant(var):
    ''' Check in ASN.1 modules if var (Primary) is declared as a constant '''
    if var is None:
        return False
    if isinstance(var, ogAST.PrimConstant):
        return True
    if DV and isinstance(var, ogAST.PrimVariable):
        for mod in DV.asn1Modules:
            for constant in DV.exportedVariables[mod]:
                if(constant.lower() == var.value[0].lower().replace('_', '-')):
                    LOG.debug('Constant ' + var.inputString + ' found')
                    return True
    return False


def fix_special_operators(op_name, expr_list, context):
    ''' Verify/fix type of special operators parameters '''
    if op_name.lower() in ('length', 'present', 'abs', 'float', 'fix'):
        if len(expr_list) != 1:
            raise AttributeError('Only one parameter for the {} operator'
                                 .format(op_name))
        expr = expr_list[0]
        if expr.exprType is UNKNOWN_TYPE:
            expr.exprType = find_variable(expr.value[0], context)
            # XXX should change type to PrimVariable
        basic = find_basic_type(expr.exprType)
        if op_name.lower() == 'length' and basic.kind != 'SequenceOfType' \
                and not is_string(basic):
            raise TypeError('Length operator works only on strings/lists')
        elif op_name.lower() == 'present' and basic.kind != 'ChoiceType':
            raise TypeError('Present operator works only on CHOICE types')
        elif op_name.lower() in ('abs', 'float', 'fix') and not is_numeric(basic):
            raise TypeError('"{}" operator needs a numerical parameter'.format(
                op_name))
    elif op_name.lower() == 'power':
        if len(expr_list) != 2:
            raise AttributeError('The "power" operator takes two parameters')
        for idx, expr in enumerate(expr_list):
            if expr.exprType is UNKNOWN_TYPE:
                expr.exprType = find_variable(expr.value[0], context)
                # XXX should change type to PrimVariable
            if idx == 0 and not is_numeric(expr.exprType):
                raise TypeError('First parameter of power must be numerical')
            elif idx == 1 and not is_integer(expr.exprType):
                raise TypeError('Second parameter of power must be integer')
    elif op_name.lower() in ('write', 'writeln'):
        for param in expr_list:
            if param.exprType is UNKNOWN_TYPE:
                for each in (INTEGER, REAL, BOOLEAN, RAWSTRING, OCTETSTRING):
                    try:
                        check_type_compatibility(param, each, context)
                        if each is OCTETSTRING and isinstance(param,
                                                         ogAST.PrimIfThenElse):
                            param.exprType = param.value['then'].exprType
                        else:
                            param.exprType = each
                        break
                    except TypeError:
                        continue
                else:
                    # Type not found among supported types
                    # Has to be a variable...otherwise, error!
                    try:
                        param.exprType = find_variable(param.value[0], context)
                    except (KeyError, AttributeError):
                        raise TypeError('Could not determine type of argument'
                                        ' "{}"'.format(param.inputString))
            basic = find_basic_type(param.exprType)
            if basic.kind not in ('IntegerType', 'Integer32Type',
                                  'RealType', 'BooleanType') \
                                and not basic.kind.endswith('StringType'):
                # Currently supported printable types
                raise TypeError('Write operator does not support type')
    elif op_name.lower() == 'set_timer':
        if len(expr_list) != 2:
            raise TypeError('SET_TIMER has 2 parameters: (int, timer_name)')
        basic = find_basic_type(expr_list[0].exprType)
        if not basic.kind.startswith('Integer'):
            raise TypeError('SET_TIMER first parameter is not an integer')
        timer = expr_list[1].inputString
        for each in chain(context.timers, context.global_timers):
            if each.lower() == timer.lower():
                break
        else:
            raise TypeError('Timer {} is not defined'.format(timer))
    elif op_name.lower == 'reset_timer':
        if len(expr_list) != 1:
            raise TypeError('RESET_TIMER has 1 parameter: timer_name')
        timer = expr_list[0].inputString
        for each in context.timers:
            if each.lower() == timer.lower():
                break
        else:
            raise TypeError('Timer {} is not defined'.format(timer))
    else:
        # TODO: other operators
        return


def check_and_fix_op_params(op_name, expr_list, context):
    '''
        Verify and/or set the type of a procedure/output parameters
        TODO: when supported, add operators
    '''
    # (1) Find the signature of the function
    # signature will hold the list of parameters for the function
    LOG.debug('[check_and_fix_op_params] ' + op_name + ' - ' + str(expr_list))
    signature = []
    key = ''

    for out_sig in context.output_signals:
        if out_sig['name'].lower() == op_name.lower():
            if out_sig.get('type'):
                # output signals: one single parameter
                signature = [{'type': out_sig.get('type'),
                              'name': out_sig.get('param_name' or ''),
                              'direction': 'in'}]
            break
    else:
        # Procedures (inner and external)
        for inner_proc in context.procedures:
            key = inner_proc.inputString
            if key.lower() == op_name.lower():
                signature = inner_proc.fpar
                break
        else:
            if op_name.lower() not in SPECIAL_OPERATORS:
                raise AttributeError('Operator/output/procedure not found: '
                    + op_name)
            else:
                # Special operators: parameters are context dependent
                fix_special_operators(op_name, expr_list, context)
                return
    # (2) Check that the number of given parameters matches the signature
    if signature is not None and len(signature) != len(expr_list):
        raise TypeError('Wrong number of parameters')
    # (3) Check each individual parameter type
    for idx, param in enumerate(expr_list):
        if signature is None:
            break
        # Get parameter type name from the function signature:
        param_type = type_name(signature[idx].get('type'))
        # Retrieve the type (or None if it is a sepecial operator)
        dataview_entry = types().get(param_type) or UNKNOWN_TYPE
        if dataview_entry is not UNKNOWN_TYPE:
            dataview_type = new_ref_type(param_type)
        else:
            dataview_type = UNKNOWN_TYPE

        expr = ogAST.ExprAssign()
        expr.left = ogAST.PrimVariable()
        expr.left.exprType = dataview_type
        expr.right = param
        fix_expression_types(expr, context)
        expr_list[idx] = expr.right
        if signature[idx].get('direction') != 'in' \
                and not isinstance(expr.right, ogAST.PrimVariable):
            raise TypeError('OUT parameter "{}" is not a variable'
                            .format(expr.right.inputString))


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, typeRef, context):
    '''
        Check if an ogAST.Primary (raw value, enumerated, ASN.1 Value...)
        is compatible with a given type (typeRef is an ASN1Scc type)
        Does not return anything if OK, otherwise raises TypeError
    '''
    assert typeRef is not None
    if typeRef is UNKNOWN_TYPE:
        raise TypeError('Type reference is unknown')
    if isinstance(primary, ogAST.PrimConstant):
        # ASN.1 constants type is unknown (Asn1 backend to be completed)
        return
    actual_type = find_basic_type(typeRef)
    LOG.debug("[check_type_compatibility] "
              "checking if {value} is of type {typeref}: "
              .format(value=primary.inputString, typeref=type_name(typeRef)))

    if (isinstance(primary, ogAST.PrimEnumeratedValue)
            and actual_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('_', '-')
        corr_type = actual_type.EnumValues.get(enumerant)
        if corr_type:
            return
        else:
            err = ('Value "' + primary.inputString +
                   '" not in this enumeration: ' +
                   str(actual_type.EnumValues.keys()))
            raise TypeError(err)
    elif isinstance(primary, ogAST.PrimIfThenElse):
        # check that IF expr returns BOOL, and that Then and Else expressions
        # are compatible with actual_type
        if_expr = primary.value['if']
        then_expr = primary.value['then']
        else_expr = primary.value['else']
        if if_expr.exprType.kind != 'BooleanType':
            raise TypeError('IF expression does not return a boolean')
        else:
            for expr in (then_expr, else_expr):
                if expr.is_raw:
                    check_type_compatibility(expr, typeRef, context)
                # compare the types for semantic equivalence:
                else:
                    if expr.exprType is UNKNOWN_TYPE:
                        # If it was not resolved before, it must be a variable
                        # this can happen in the context of a special operator
                        # (write), where at no point before where the type
                        # could be compared to another type
                        expr.exprType = find_variable(expr.value[0], context)
                    compare_types(expr.exprType, typeRef)
        return
    elif isinstance(primary, ogAST.PrimVariable):
        try:
            compare_types(primary.exprType, typeRef)
        except TypeError as err:
            raise TypeError('{expr} should be of type {ty} - {err}'
                            .format(expr=primary.inputString,
                                    ty=type_name(typeRef),
                                    err=str(err)))
        return
    elif isinstance(primary, ogAST.PrimInteger) \
            and actual_type.kind.startswith('Integer'):
        return

    elif isinstance(primary, ogAST.PrimReal) \
            and actual_type.kind.startswith('Real'):
        return

    elif isinstance(primary, ogAST.PrimBoolean) \
            and actual_type.kind.startswith('Boolean'):
        return
    elif (isinstance(primary, ogAST.PrimEmptyString) and
                                         actual_type.kind == 'SequenceOfType'):
        if int(actual_type.Min) == 0:
            return
        else:
            raise TypeError('SEQUENCE OF has a minimum size of '
                            + actual_type.Min + ')')
    elif isinstance(primary, ogAST.PrimSequenceOf) \
            and actual_type.kind == 'SequenceOfType':
        if (len(primary.value) < int(actual_type.Min) or
                len(primary.value) > int(actual_type.Max)):
            raise TypeError(str(len(primary.value)) +
                      ' elements in SEQUENCE OF, while constraint is [' +
                      str(actual_type.Min) + '..' + str(actual_type.Max) + ']')
        for elem in primary.value:
            check_type_compatibility(elem, actual_type.type, context)
        return
    elif isinstance(primary, ogAST.PrimSequence) \
            and actual_type.kind == 'SequenceType':
        user_nb_elem = len(primary.value.keys())
        type_nb_elem = len(actual_type.Children.keys())
        if user_nb_elem != type_nb_elem:
            raise TypeError('Wrong number of fields in SEQUENCE of type {}'
                            .format(type_name(typeRef)))
        else:
            for field, fd_data in actual_type.Children.viewitems():
                ufield = field.replace('-', '_')
                if ufield not in primary.value:
                    raise TypeError('Missing field {field} in SEQUENCE'
                                    ' of type {t1} '
                                    .format(field=ufield,
                                            t1=type_name(typeRef)))
                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 actual_type.kind.startswith('Choice'):
        for choicekey, choice in actual_type.Children.viewitems():
            if choicekey.lower() == primary.value['choice'].lower():
                break
        else:
            raise TypeError('Non-existent choice "{choice}" in type {t1}'
                            .format(choice=primary.value['choice'],
                            t1=type_name(typeRef)))
        # compare primary.value['value']
        # with actual_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 actual_type.kind.startswith('Choice'):
        for choicekey, choice in actual_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(typeRef)))

    elif isinstance(primary, ogAST.PrimStringLiteral):
        # Octet strings
        basic_type = find_basic_type(typeRef)
        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
                                            actual_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(typeRef)))


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
    # Check if both types have basic compatibility
    simple_types = [elem for elem in (type_a, type_b) if elem.kind in
                       ('IntegerType', 'BooleanType', 'RealType', 'StringType',
                        'SequenceOfType', 'Integer32Type', 'OctetStringType')]
    if len(simple_types) < 2:
        # Either A or B is not a basic type - cannot be compatible
        raise TypeError('One of the types is not a basic type: '
                + type_name(type_a) + ' or ' + type_name(type_b))
    elif type_a.kind == type_b.kind:
        if type_a.kind == 'SequenceOfType':
            if type_a.Min == type_b.Min and type_a.Max == type_b.Max:
                compare_types(type_a.type, type_b.type)
                return
            else:
                raise TypeError('Incompatible arrays')
        return
    elif type_a.kind.endswith('StringType') and type_b.kind.endswith('StringType'):
        # Allow Octet String values to be printable strings.. for convenience
        return
    elif not(type_a.kind in ('IntegerType', 'Integer32Type') and
             type_b.kind in ('IntegerType', 'Integer32Type')):
        raise TypeError('One type is an integer, not the other one')
    elif any(side.kind == 'RealType' for side in (type_a, type_b)):
        raise TypeError('One type is an REAL, not the other one')
    elif all(side.kind.startswith('Integer') for side in (type_a, type_b)) \
            or all(side.kind == 'RealType' for side in (type_a, type_b)):
        pass
    else:
        return


def find_variable(var, context):
    ''' Look for a variable name in the context and return its type '''
    result = UNKNOWN_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():
                LOG.debug(str(var) + ' is defined')
                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():
            result = vartype
            LOG.debug(str(var) + ' is defined')
            return result
    for timer in chain(context.timers, context.global_timers):
        if var.lower() == timer.lower():
            LOG.debug(str(var) + ' is defined')
            return result

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


def fix_expression_types(expr, context):
    ''' Check/ensure type consistency in binary expressions '''
    # If a side of the expression is of Enumerated or Choice type, check if
    # the other side is a literal of that sort, and change type accordingly
    for side in permutations(('left', 'right')):
        side_type = find_basic_type(getattr(expr, side[0]).exprType).kind
        if side_type == 'EnumeratedType':
            prim = ogAST.PrimEnumeratedValue(primary=getattr(expr, side[1]))
        elif side_type == 'ChoiceEnumeratedType':
            prim = ogAST.PrimChoiceDeterminant(primary=getattr(expr, side[1]))
        try:
            check_type_compatibility(prim, getattr(expr, side[0]).exprType,
                                     context)
            setattr(expr, side[1], prim)
            getattr(expr, side[1]).exprType = getattr(expr, side[0]).exprType
        except (UnboundLocalError, AttributeError, TypeError):
            pass

    # If a side type remains unknown, check if it is an ASN.1 constant
    for side in permutations(('left', 'right')):
        value = getattr(expr, side[0])
        if value.exprType == UNKNOWN_TYPE and is_constant(value):
            setattr(expr, side[0], ogAST.PrimConstant(primary=value))
            getattr(expr, side[0]).exprType = getattr(expr, side[1]).exprType

    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 in permutations(('left', 'right')):
        value = getattr(expr, side[0])  # get expr.left then expr.right
        if not isinstance(value, ogAST.PrimSequenceOf):
            continue
        other = getattr(expr, side[1])  # 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:
            raise TypeError('Cannot resolve type of "{}"'
                            .format(unknown[0].inputString))

    # In Sequence, Choice, SEQUENCE OF, and IfThenElse 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.PrimIfThenElse):
        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)
        if not raw_expr.exprType.kind.startswith(('Integer', 'Real')):
            # Raw int/real must keep their type because of the range
            # that can be computed
            raw_expr.exprType = ref_type
    else:
        compare_types(expr.left.exprType, expr.right.exprType)


def expression_list(root, context):
    ''' Parse a list of expression parameters '''
    errors = []
    warnings = []
    result = []
    for param in root.getChildren():
        exp, err, warn = expression(param, context)
        errors.extend(err)
        warnings.extend(warn)
        result.append(exp)
    return result, errors, warnings


def primary_variable(root, context):
    ''' Primary Variable analysis '''
    lexeme = root.children[0].text

    # Differentiate DCL and FPAR variables
    Prim = ogAST.PrimVariable
    if isinstance(context, ogAST.Procedure):
        for each in context.fpar:
            if each['name'].lower() == lexeme.lower():
                Prim = ogAST.PrimFPAR
                break

    prim, errors, warnings = Prim(), [], []
    prim.value = [root.children[0].text]
    prim.exprType = UNKNOWN_TYPE
    prim.inputString = get_input_string(root)
    prim.tmpVar = tmp()

    try:
        prim.exprType = find_variable(lexeme, context)
    except AttributeError:
        pass

    return prim, errors, warnings


def binary_expression(root, context):
    ''' Binary expression analysys '''
    errors, warnings = [], []

    ExprNode = EXPR_NODE[root.type]
    expr = ExprNode(
        get_input_string(root),
        root.getLine(),
        root.getCharPositionInLine()
    )
    expr.exprType = UNKNOWN_TYPE
    expr.tmpVar = tmp()

    left, right = root.children
    expr.left, err_left, warn_left = expression(left, context)
    expr.right, err_right, warn_right = expression(right, context)
    errors.extend(err_left)
    warnings.extend(warn_left)
    errors.extend(err_right)
    warnings.extend(warn_right)

    try:
        fix_expression_types(expr, context)
    except (AttributeError, TypeError) as err:
        errors.append(error(root, str(err)))

    return expr, errors, warnings


def unary_expression(root, context):
    ''' Unary expression analysys '''
    ExprNode = EXPR_NODE[root.type]
    expr = ExprNode(
        get_input_string(root),
        root.getLine(),
        root.getCharPositionInLine()
    )
    expr.exprType = UNKNOWN_TYPE
    expr.tmpVar = tmp()

    expr.expr, errors, warnings = expression(root.children[0], context)

    return expr, errors, warnings


def expression(root, context):
    ''' Expression analysis (e.g. 5+5*hello(world)!foo) '''
    logic = (lexer.OR, lexer.AND, lexer.XOR)
    arithmetic = (lexer.PLUS, lexer.ASTERISK, lexer.DASH,
                  lexer.DIV, lexer.MOD, lexer.REM)
    relational = (lexer.EQ, lexer.NEQ, lexer.GT, lexer.GE, lexer.LT, lexer.LE)

    if root.type in logic:
        return logic_expression(root, context)
    elif root.type in arithmetic:
        return arithmetic_expression(root, context)
    elif root.type in relational:
        return relational_expression(root, context)
    elif root.type == lexer.IN:
        return in_expression(root, context)
    elif root.type == lexer.APPEND:
        return append_expression(root, context)