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) 2012-2018 European Space Agency

    Designed and implemented by Maxime Perrotin

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

__author__ = 'Maxime Perrotin'

import sys
import os
import math
import operator
import logging
import traceback
import binascii
from textwrap import dedent
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,
} # type: Dict[int, ogAST.Expression]

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

DV = None  # type: module

# 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  # type: int

# 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)})
UNSIGNED = type('IntegerType', (object,), {'kind': 'IntegerType',
                                          'Min': "0",
                                          'Max': str(2 ** 64 - 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': UNSIGNED, '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):
    # type: (List[str]) -> None
    ''' Call ASN.1 parser and set the global dataview AST entry (DV) '''
    global DV
    if '--toC' in sys.argv:
        rename_policy = ASN1.RenameOnlyConflicting
    else:
        rename_policy = ASN1.NoRename
    try:
        DV = parse_asn1(tuple(asn1_filenames),
                        ast_version=ASN1.UniqueEnumeratedNames,
                        rename_policy=rename_policy,
                        flags=[ASN1.AstOnly],
                        pretty_print=True)
    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):
    # type: (ogAST.PrimSubstring) -> Tuple[str, str]
    ''' 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):
    # type: (Any) -> bool
    ''' Return true if a type is an Integer Type '''
    return find_basic_type(ty).kind in (
        'IntegerType',
        'Integer32Type'
    )


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


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


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


def is_null(ty):
    # type: (Any) -> bool
    ''' Return true if a type is a NULL Type '''
    return find_basic_type(ty).kind == 'NullType'


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


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


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


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


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


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


def is_timer(ty):
    # type: (Any) -> bool
    ''' 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.lower() == process_name.lower():
                return process
            elif process.instance_of_name.lower() == process_name.lower():
                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
        process_name can be the name of a process type, in which case the
        interfaces can only be found by looking at an instance of the type
        that is actually connected in the system
    '''
    all_signals, async_signals, errors = [], [], set()
    system = ast

    # 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
    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)
        # Update process name with the name of the instance if we are parsing
        # a process type.
        if process_ref:
            process_name = process_ref.processName
            # 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)
                except (KeyError, AttributeError) as err:
                    # Exceptions raised if a signal is not defined, i.e. there
                    # if an empty signal entry in the list. This can happen
                    # if the name of the signal is a reserved keyword, such as
                    # "stop", "reset"...
                    errors.add('Check the names of your signals against'
                               ' reserved keywords')
    if undeclared_signals:
        errors.add('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):
    # type: (Any, str) -> str
    ''' Return an error message '''
    return '{} - "{}"'.format(msg, get_input_string(root))


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


def tmp():
    # type : () -> int
    ''' 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 (value-returning functions only,
        i.e not signal sending '''

    # 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) or \
                    is_enumerated(p_ty):
                continue
            raise TypeError('Type {} not supported in call to {}'.
                format(type_name(p.exprType), name))
        return UNKNOWN_TYPE

    # (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):
        warnings = []
        expr = ogAST.ExprAssign()
        expr.left = ogAST.PrimVariable()
        expr.left.exprType = sign[idx]['type']
        expr.right = param

        try:
            basic_left  = find_basic_type(expr.left.exprType)
            basic_right = find_basic_type(expr.right.exprType)
            #print getattr(basic_left, "Min", 0), getattr(basic_right, "Min", 0)
            warnings.extend(fix_expression_types(expr, context))
            params[idx] = expr.right
        except TypeError as err:
            expected = type_name(sign[idx]['type'])
            received = type_name(expr.right.exprType)
            raise TypeError('In call to {}: Type of parameter {} is incorrect'
                            ' ({}) - {}'
                            .format(name, idx+1, received, str(err)))
        if (warnings):
            expected = type_name(sign[idx]['type'])
            received = type_name(expr.right.exprType)
            raise Warning('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':
        # The implementation of abs in *all* progamming languages returns
        # a type that is the same as the type of the parameter. The returned
        # value is *not* unsigned. abs(integer'Min) returns a NEGATIVE number
        return type('Abs', (param_btys[0],), {})
#       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', (INT32,), {
            '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)))
        })

    else:
        # check if procedure is declared to return a type
        for inner_proc in context.procedures:
            proc_name = inner_proc.inputString
            if proc_name.lower() == name.lower() and inner_proc.return_type:
                return inner_proc.return_type

    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 Warning('Expression evaluation in range [{}..{}], '
                          'could be outside expected range [{}..{}]'
                    .format(type_to_check.Min, type_to_check.Max,
                            typeref.Min, typeref.Max))
    except (AttributeError, ValueError):
        raise TypeError('Missing range')


def fix_append_expression_type(expr, expected_type):
    ''' In an Append expression, all components must be of the same type,
        which is the type expected by the user of the append, for example 
        the left part of an assign expression.
        We must recursively fix the Append type, in case we have a//b//c
        that is handled as (a//b)//c
        Inputs:
           expr: the append expression (possibly recursive)
           expected_type : the type to assign to the expression
    '''
    def rec_append(inner_expr, set_type):
        for each in (inner_expr.left, inner_expr.right):
            if isinstance(each, ogAST.ExprAppend):
                rec_append(each, set_type)
            each.expected_type = set_type
    rec_append(expr, expected_type)
    expr.exprType      = expected_type
    expr.expected_type = expected_type


def check_type_compatibility(primary, type_ref, context):  # type: -> [warnings]
    '''
        Check if an ogAST.Primary (raw value, enumerated, ASN.1 Value...)
        is compatible with a given type (type_ref is an ASN1Scc type)
        Possibly returns a list of warnings; can raises TypeError
    '''
    warnings = []    # function returns a list of warnings
    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)

    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 warnings
        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:
                warnings.extend(check_type_compatibility(expr,
                                                         type_ref,
                                                         context))
        return warnings

    elif isinstance(primary, (ogAST.PrimVariable, ogAST.PrimSelector)):
        try:
            warnings.extend(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 warnings

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

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

    elif isinstance(primary, ogAST.ExprNeg):
        warnings.extend(check_type_compatibility(primary.expr,
                                                 type_ref,
                                                 context))

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

    elif isinstance(primary, ogAST.PrimNull) and is_null(type_ref):
        return warnings

    elif isinstance(primary, ogAST.PrimEmptyString):
        # Empty strings ("{ }") can be used for arrays and empty records
        if basic_type.kind == 'SequenceOfType':
            if int(basic_type.Min) == 0:
                return warnings
            else:
                raise TypeError('SEQUENCE OF has a minimum size of '
                                + basic_type.Min + ')')
        elif basic_type.kind == 'SequenceType':
            if len(basic_type.Children.keys()) > 0:
                raise TypeError('SEQUENCE is not empty, wrong "{}" syntax')
        else:
            raise TypeError('Not a type compatible with empty string syntax')
    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)):
            #print traceback.print_stack()
            raise TypeError(str(len(primary.value)) +
                      ' element(s) in SEQUENCE OF, while constraint is [' +
                      str(basic_type.Min) + ' .. ' + str(basic_type.Max) + ']')
        for elem in primary.value:
            warnings.extend(check_type_compatibility(elem,
                                                     basic_type.type,
                                                     context))
        if not hasattr(primary, 'expected_type') \
               and type_ref.__name__ not in ('Apnd', 'SubStr'):
            primary.expected_type = type_ref
        return warnings
    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()]
        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 ufield.lower() not in user_fields:
                # Optional field not set - OK
                continue
            else:
                # If the user field is a raw value
                casefield = ufield
                for each in primary.value:
                    if each.lower() == ufield.lower():
                        casefield = each
                        break
                if primary.value[casefield].is_raw:
                    warnings.extend(check_type_compatibility
                                         (primary.value[casefield],
                                          fd_data.type,
                                          context))
                else:
                    # Compare the types for semantic equivalence
                    try:
                        warnings.extend(compare_types
                                       (primary.value[casefield].exprType,
                                        fd_data.type))
                    except TypeError as err:
                        raise TypeError('Field "' + ufield + '" not of type ' +
                                    type_name(fd_data.type) +
                                    ' - ' + str(err))
        return warnings
    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:
            warnings.extend(check_type_compatibility(value,
                                                     choice_field_type,
                                                     context))
        # Compare the types for semantic equivalence:
        else:
            try:
                warnings.extend(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 warnings
    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 warnings
        elif basic_type.kind.endswith('StringType'):
            try:
                if int(basic_type.Min) <= len(
                        primary.value[1:-1]) <= int(basic_type.Max):
                    return warnings
                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)))
            except ValueError:
                # No size constraint (or MIN/MAX)
                LOG.debug('String literal size constraint discarded')
                return warnings
        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 warnings
    else:
        raise TypeError('{prim} does not match type {t1}'
                        .format(prim=primary.inputString,
                                t1=type_name(type_ref)))
    return warnings


def compare_types(type_a, type_b):   # type -> [warnings]
    '''
       Compare two types, return if they are semantically equivalent,
       otherwise raise TypeError
    '''
    warnings = []
    mismatch = ''
    if type_a.kind == 'ReferenceType' and type_b.kind == 'ReferenceType':
        if type_a.ReferencedTypeName != type_b.ReferencedTypeName:
            mismatch = '"{}" is not "{}"'.format(type_a.ReferencedTypeName,
                                                 type_b.ReferencedTypeName)
    type_a = find_basic_type(type_a)
    type_b = find_basic_type(type_b)

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

    # Check if both types have basic compatibility
    if type_a.kind == type_b.kind:
        if type_a.kind == 'SequenceOfType':
            if mismatch:
                raise TypeError(mismatch)
            if type_a.Min == type_a.Max:
                if type_a.Min == type_b.Min == type_b.Max:
                    warnings.extend(compare_types(type_a.type, type_b.type))
                    return warnings
                else:
                    raise TypeError('Incompatible sizes - size of {} can vary'
                                    .format(type_name(type_b)))
            elif(float(type_b.Min) >= float(type_a.Min)
                 and float(type_b.Max) <= float(type_a.Max)):
                warnings.extend(compare_types(type_a.type, type_b.type))
                return warnings
            else:
                warnings.extend(compare_types(type_a.type, type_b.type))
                warnings.append('Size constraints mismatch - risk of overflow')
                return warnings
        # TODO: Check that OctetString types have compatible range
        elif type_a.kind == 'SequenceType' and mismatch:
            raise TypeError(mismatch)
        elif type_a.kind == 'IntegerType':
            # Detect Signed/Unsigned type mismatch
            min_a, min_b = float(type_a.Min), float(type_b.Min)
            if (min_a >= 0) != (min_b >= 0):
                raise TypeError("Signed vs Unsigned type mismatch " +
                        mismatch)
            elif mismatch:
                warnings.append(mismatch)
        elif mismatch:
            warnings.append(mismatch)
        #print traceback.print_stack()
        return warnings
    elif is_string(type_a) and is_string(type_b):
        return warnings
    elif is_integer(type_a) and is_integer(type_b):
        if mismatch:
            warnings.append(mismatch)
        return warnings
    elif is_real(type_a) and is_real(type_b):
        if mismatch:
            warnings.append(mismatch)
        return warnings
    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 '''

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

    # First check locally, i.e. in FPAR