| 1 | #!/usr/bin/env python2
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| 2 | """
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| 3 | test_cast.py
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| 4 | """
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| 5 | from __future__ import print_function
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| 6 |
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| 7 | import os
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| 8 | from typing import Tuple, cast
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| 9 |
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| 10 | from mycpp import mylib
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| 11 | from mycpp.mylib import log, tagswitch
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| 12 |
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| 13 |
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| 14 | class ColorOutput(object):
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| 15 | """Abstract base class for plain text, ANSI color, and HTML color."""
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| 16 |
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| 17 | def __init__(self, f):
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| 18 | # type: (mylib.Writer) -> None
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| 19 | self.f = f
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| 20 | self.num_chars = 0
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| 21 |
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| 22 | def WriteRaw(self, raw):
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| 23 | # type: (Tuple[str, int]) -> None
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| 24 | """
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| 25 | Write raw data without escaping, and without counting control codes in the
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| 26 | length.
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| 27 | """
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| 28 | s, num_chars = raw
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| 29 | self.f.write(s)
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| 30 | self.num_chars += num_chars
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| 31 |
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| 32 | def GetRaw(self):
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| 33 | # type: () -> Tuple[str, int]
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| 34 |
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| 35 | # NOTE: Ensured by NewTempBuffer()
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| 36 | f = cast(mylib.BufWriter, self.f)
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| 37 | return f.getvalue(), self.num_chars
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| 38 |
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| 39 |
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| 40 | def TestCastBufWriter():
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| 41 | # type: () -> None
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| 42 | """For debugging a problem with StackRoots generation"""
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| 43 |
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| 44 | f = mylib.BufWriter()
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| 45 | out = ColorOutput(f)
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| 46 | out.WriteRaw(('yo', 2))
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| 47 | s, num_chars = out.GetRaw()
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| 48 | print(s)
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| 49 |
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| 50 |
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| 51 | class value_t:
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| 52 |
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| 53 | def __init__(self):
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| 54 | # type: () -> None
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| 55 | pass
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| 56 |
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| 57 | def tag(self):
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| 58 | # type: () -> int
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| 59 | raise NotImplementedError()
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| 60 |
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| 61 |
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| 62 | class value__Int(value_t):
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| 63 |
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| 64 | def __init__(self, i):
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| 65 | # type: (int) -> None
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| 66 | self.i = i
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| 67 |
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| 68 | def tag(self):
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| 69 | # type: () -> int
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| 70 | return 1
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| 71 |
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| 72 |
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| 73 | class value__Eggex(value_t):
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| 74 |
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| 75 | def __init__(self, ere):
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| 76 | # type: (str) -> None
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| 77 | self.ere = ere
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| 78 |
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| 79 | def tag(self):
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| 80 | # type: () -> int
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| 81 | return 2
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| 82 |
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| 83 |
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| 84 | def TestSwitchDowncast(val):
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| 85 | # type: (value_t) -> None
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| 86 | """
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| 87 | The common val -> UP_val -> val pattern
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| 88 | """
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| 89 | UP_val = val
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| 90 | with tagswitch(val) as case:
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| 91 | if case(1):
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| 92 | val = cast(value__Int, UP_val)
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| 93 | print('Int = %d' % val.i)
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| 94 | elif case(2):
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| 95 | val = cast(value__Eggex, UP_val)
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| 96 | print('Eggex = %r' % val.ere)
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| 97 | else:
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| 98 | print('other')
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| 99 |
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| 100 |
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| 101 | def TestSwitchDowncastBad(val):
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| 102 | # type: (value_t) -> None
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| 103 | """
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| 104 | TODO: Could we insert the UP_val automatically?
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| 105 |
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| 106 | Possible rules:
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| 107 |
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| 108 | (1) with tagswitch(cell.val) translates to
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| 109 |
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| 110 | value_t* UP_val = cell->val;
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| 111 | switch (val) {
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| 112 |
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| 113 | (2) You need MyPy casts sometimes
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| 114 |
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| 115 | unrelated = None
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| 116 | with tagswitch(val) as case:
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| 117 | if case(value_e.Int):
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| 118 | val = cast(value.Int, val)
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| 119 | print('i = %d' % val.i)
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| 120 |
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| 121 | elif case(value_e.Str):
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| 122 | unrelated = cast(str, obj)
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| 123 | print('String')
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| 124 |
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| 125 | (3) Then the C++ casts would look like:
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| 126 |
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| 127 | value_t* UP_val = cell->val;
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| 128 | switch (val) {
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| 129 | case value_e::Int {
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| 130 | # How do we know to generate a NEW var here, without the UP_val
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| 131 | # heuristic?
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| 132 | #
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| 133 | # OK well we can simply use the switch variable name? It it
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| 134 | # matches, we create a new var.
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| 135 | #
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| 136 | # Technical problem: it's INSIDE a block, so we have to "look
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| 137 | # ahead" to the first thing in the block.
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| 138 |
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| 139 | value::Int* val = static_cast<value::Int*>(val);
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| 140 | }
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| 141 | case value_e::Str {
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| 142 | // NOT a new variable
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| 143 | unrelated = static_cast<Str*>(obj);
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| 144 | }
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| 145 | }
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| 146 | """
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| 147 |
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| 148 | #UP_val = val
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| 149 | with tagswitch(val) as case:
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| 150 | if case(1):
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| 151 | val = cast(value__Int, val)
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| 152 | print('Int')
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| 153 | #print('Int = %d' % val.i)
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| 154 | elif case(2):
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| 155 | val = cast(value__Eggex, val)
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| 156 | print('Eggex')
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| 157 | # If we enable this, then it fails to compile
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| 158 | #print('Eggex = %r' % val.ere)
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| 159 | else:
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| 160 | print('other')
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| 161 |
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| 162 |
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| 163 | def TestCastInSwitch():
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| 164 | # type: () -> None
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| 165 |
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| 166 | # Inspired by HasAffix()
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| 167 |
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| 168 | e = value__Eggex('[0-9]+')
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| 169 |
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| 170 | pattern_val = e # type: value_t
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| 171 |
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| 172 | pattern_eggex = None # type: value__Eggex
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| 173 | i = 42
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| 174 | with tagswitch(pattern_val) as case:
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| 175 | if case(1): # Int
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| 176 | raise AssertionError()
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| 177 | elif case(2):
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| 178 | pattern_eggex = cast(value__Eggex, pattern_val)
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| 179 | else:
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| 180 | raise AssertionError()
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| 181 |
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| 182 | print('eggex = %r' % pattern_eggex.ere)
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| 183 |
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| 184 |
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| 185 | def run_tests():
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| 186 | # type: () -> None
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| 187 |
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| 188 | # This should (void)unused2; on the same line
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| 189 | unused2 = 42
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| 190 |
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| 191 | TestCastBufWriter()
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| 192 | TestSwitchDowncast(value__Eggex('[0-9]'))
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| 193 | TestSwitchDowncast(value__Int(42))
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| 194 |
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| 195 | TestSwitchDowncastBad(value__Eggex('[0-9]'))
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| 196 | TestSwitchDowncastBad(value__Int(42))
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| 197 |
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| 198 | TestCastInSwitch()
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| 199 |
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| 200 |
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| 201 | def run_benchmarks():
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| 202 | # type: () -> None
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| 203 | raise NotImplementedError()
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| 204 |
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| 205 |
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| 206 | if __name__ == '__main__':
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| 207 | if os.getenv('BENCHMARK'):
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| 208 | log('Benchmarking...')
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| 209 | run_benchmarks()
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| 210 | else:
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| 211 | run_tests()
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