From 60d343a81679ea90ae0e08fadcd132c16906a51a Mon Sep 17 00:00:00 2001 From: Tal Einat <532281+taleinat@users.noreply.github.com> Date: Wed, 19 May 2021 12:18:10 +0300 Subject: [PATCH] bpo-44010: IDLE: colorize pattern-matching soft keywords (GH-25851) --- Doc/library/idle.rst | 6 + Doc/whatsnew/3.10.rst | 6 + Lib/idlelib/colorizer.py | 135 ++++++---- Lib/idlelib/help.html | 27 +- Lib/idlelib/idle_test/test_colorizer.py | 239 ++++++++++++++++-- .../2021-05-09-09-02-09.bpo-44010.TaLe9x.rst | 5 + 6 files changed, 345 insertions(+), 73 deletions(-) create mode 100644 Misc/NEWS.d/next/IDLE/2021-05-09-09-02-09.bpo-44010.TaLe9x.rst diff --git a/Doc/library/idle.rst b/Doc/library/idle.rst index 3c302115b5f..faa34e69ff1 100644 --- a/Doc/library/idle.rst +++ b/Doc/library/idle.rst @@ -613,6 +613,12 @@ keywords, builtin class and function names, names following ``class`` and ``def``, strings, and comments. For any text window, these are the cursor (when present), found text (when possible), and selected text. +IDLE also highlights the :ref:`soft keywords ` :keyword:`match`, +:keyword:`case `, and :keyword:`_ ` in +pattern-matching statements. However, this highlighting is not perfect and +will be incorrect in some rare cases, including some ``_``-s in ``case`` +patterns. + Text coloring is done in the background, so uncolorized text is occasionally visible. To change the color scheme, use the Configure IDLE dialog Highlighting tab. The marking of debugger breakpoint lines in the editor and diff --git a/Doc/whatsnew/3.10.rst b/Doc/whatsnew/3.10.rst index 926679e6f32..570af7f3b61 100644 --- a/Doc/whatsnew/3.10.rst +++ b/Doc/whatsnew/3.10.rst @@ -1030,6 +1030,12 @@ Terry Jan Reedy in :issue:`37892`.) We expect to backport these shell changes to a future 3.9 maintenance release. +Highlight the new :ref:`soft keywords ` :keyword:`match`, +:keyword:`case `, and :keyword:`_ ` in +pattern-matching statements. However, this highlighting is not perfect +and will be incorrect in some rare cases, including some ``_``-s in +``case`` patterns. (Contributed by Tal Einat in bpo-44010.) + importlib.metadata ------------------ diff --git a/Lib/idlelib/colorizer.py b/Lib/idlelib/colorizer.py index 3c527409731..e9f19c145c8 100644 --- a/Lib/idlelib/colorizer.py +++ b/Lib/idlelib/colorizer.py @@ -16,6 +16,32 @@ def any(name, alternates): def make_pat(): kw = r"\b" + any("KEYWORD", keyword.kwlist) + r"\b" + match_softkw = ( + r"^[ \t]*" + # at beginning of line + possible indentation + r"(?Pmatch)\b" + + r"(?![ \t]*(?:" + "|".join([ # not followed by ... + r"[:,;=^&|@~)\]}]", # a character which means it can't be a + # pattern-matching statement + r"\b(?:" + r"|".join(keyword.kwlist) + r")\b", # a keyword + ]) + + r"))" + ) + case_default = ( + r"^[ \t]*" + # at beginning of line + possible indentation + r"(?Pcase)" + + r"[ \t]+(?P_\b)" + ) + case_softkw_and_pattern = ( + r"^[ \t]*" + # at beginning of line + possible indentation + r"(?Pcase)\b" + + r"(?![ \t]*(?:" + "|".join([ # not followed by ... + r"_\b", # a lone underscore + r"[:,;=^&|@~)\]}]", # a character which means it can't be a + # pattern-matching case + r"\b(?:" + r"|".join(keyword.kwlist) + r")\b", # a keyword + ]) + + r"))" + ) builtinlist = [str(name) for name in dir(builtins) if not name.startswith('_') and name not in keyword.kwlist] @@ -27,12 +53,29 @@ def make_pat(): sq3string = stringprefix + r"'''[^'\\]*((\\.|'(?!''))[^'\\]*)*(''')?" dq3string = stringprefix + r'"""[^"\\]*((\\.|"(?!""))[^"\\]*)*(""")?' string = any("STRING", [sq3string, dq3string, sqstring, dqstring]) - return (kw + "|" + builtin + "|" + comment + "|" + string + - "|" + any("SYNC", [r"\n"])) + prog = re.compile("|".join([ + builtin, comment, string, kw, + match_softkw, case_default, + case_softkw_and_pattern, + any("SYNC", [r"\n"]), + ]), + re.DOTALL | re.MULTILINE) + return prog -prog = re.compile(make_pat(), re.S) -idprog = re.compile(r"\s+(\w+)", re.S) +prog = make_pat() +idprog = re.compile(r"\s+(\w+)") +prog_group_name_to_tag = { + "MATCH_SOFTKW": "KEYWORD", + "CASE_SOFTKW": "KEYWORD", + "CASE_DEFAULT_UNDERSCORE": "KEYWORD", + "CASE_SOFTKW2": "KEYWORD", +} + + +def matched_named_groups(re_match): + "Get only the non-empty named groups from an re.Match object." + return ((k, v) for (k, v) in re_match.groupdict().items() if v) def color_config(text): @@ -231,14 +274,10 @@ class ColorDelegator(Delegator): def recolorize_main(self): "Evaluate text and apply colorizing tags." next = "1.0" - while True: - item = self.tag_nextrange("TODO", next) - if not item: - break - head, tail = item - self.tag_remove("SYNC", head, tail) - item = self.tag_prevrange("SYNC", head) - head = item[1] if item else "1.0" + while todo_tag_range := self.tag_nextrange("TODO", next): + self.tag_remove("SYNC", todo_tag_range[0], todo_tag_range[1]) + sync_tag_range = self.tag_prevrange("SYNC", todo_tag_range[0]) + head = sync_tag_range[1] if sync_tag_range else "1.0" chars = "" next = head @@ -256,23 +295,8 @@ class ColorDelegator(Delegator): return for tag in self.tagdefs: self.tag_remove(tag, mark, next) - chars = chars + line - m = self.prog.search(chars) - while m: - for key, value in m.groupdict().items(): - if value: - a, b = m.span(key) - self.tag_add(key, - head + "+%dc" % a, - head + "+%dc" % b) - if value in ("def", "class"): - m1 = self.idprog.match(chars, b) - if m1: - a, b = m1.span(1) - self.tag_add("DEFINITION", - head + "+%dc" % a, - head + "+%dc" % b) - m = self.prog.search(chars, m.end()) + chars += line + self._add_tags_in_section(chars, head) if "SYNC" in self.tag_names(next + "-1c"): head = next chars = "" @@ -291,6 +315,40 @@ class ColorDelegator(Delegator): if DEBUG: print("colorizing stopped") return + def _add_tag(self, start, end, head, matched_group_name): + """Add a tag to a given range in the text widget. + + This is a utility function, receiving the range as `start` and + `end` positions, each of which is a number of characters + relative to the given `head` index in the text widget. + + The tag to add is determined by `matched_group_name`, which is + the name of a regular expression "named group" as matched by + by the relevant highlighting regexps. + """ + tag = prog_group_name_to_tag.get(matched_group_name, + matched_group_name) + self.tag_add(tag, + f"{head}+{start:d}c", + f"{head}+{end:d}c") + + def _add_tags_in_section(self, chars, head): + """Parse and add highlighting tags to a given part of the text. + + `chars` is a string with the text to parse and to which + highlighting is to be applied. + + `head` is the index in the text widget where the text is found. + """ + for m in self.prog.finditer(chars): + for name, matched_text in matched_named_groups(m): + a, b = m.span(name) + self._add_tag(a, b, head, name) + if matched_text in ("def", "class"): + if m1 := self.idprog.match(chars, b): + a, b = m1.span(1) + self._add_tag(a, b, head, "DEFINITION") + def removecolors(self): "Remove all colorizing tags." for tag in self.tagdefs: @@ -299,27 +357,14 @@ class ColorDelegator(Delegator): def _color_delegator(parent): # htest # from tkinter import Toplevel, Text + from idlelib.idle_test.test_colorizer import source from idlelib.percolator import Percolator top = Toplevel(parent) top.title("Test ColorDelegator") x, y = map(int, parent.geometry().split('+')[1:]) - top.geometry("700x250+%d+%d" % (x + 20, y + 175)) - source = ( - "if True: int ('1') # keyword, builtin, string, comment\n" - "elif False: print(0)\n" - "else: float(None)\n" - "if iF + If + IF: 'keyword matching must respect case'\n" - "if'': x or'' # valid keyword-string no-space combinations\n" - "async def f(): await g()\n" - "# All valid prefixes for unicode and byte strings should be colored.\n" - "'x', '''x''', \"x\", \"\"\"x\"\"\"\n" - "r'x', u'x', R'x', U'x', f'x', F'x'\n" - "fr'x', Fr'x', fR'x', FR'x', rf'x', rF'x', Rf'x', RF'x'\n" - "b'x',B'x', br'x',Br'x',bR'x',BR'x', rb'x', rB'x',Rb'x',RB'x'\n" - "# Invalid combinations of legal characters should be half colored.\n" - "ur'x', ru'x', uf'x', fu'x', UR'x', ufr'x', rfu'x', xf'x', fx'x'\n" - ) + top.geometry("700x550+%d+%d" % (x + 20, y + 175)) + text = Text(top, background="white") text.pack(expand=1, fill="both") text.insert("insert", source) diff --git a/Lib/idlelib/help.html b/Lib/idlelib/help.html index e80384b7775..19041c6054e 100644 --- a/Lib/idlelib/help.html +++ b/Lib/idlelib/help.html @@ -5,7 +5,7 @@ - IDLE — Python 3.10.0a6 documentation + IDLE — Python 3.11.0a0 documentation @@ -18,7 +18,7 @@ @@ -71,7 +71,7 @@
  • - 3.10.0a6 Documentation » + 3.11.0a0 Documentation »
  • The Python Standard Library »
    • @@ -102,7 +102,7 @@

    IDLE

    -

    Source code: Lib/idlelib/

    +

    Source code: Lib/idlelib/

    IDLE is Python’s Integrated Development and Learning Environment.

    IDLE has the following features:

    @@ -581,6 +581,11 @@ user error. For Python code, at the shell prompt or in an editor, these are keywords, builtin class and function names, names following class and def, strings, and comments. For any text window, these are the cursor (when present), found text (when possible), and selected text.

    +

    IDLE also highlights the soft keywords match, +case, and _ in +pattern-matching statements. However, this highlighting is not perfect and +will be incorrect in some rare cases, including some _-s in case +patterns.

    Text coloring is done in the background, so uncolorized text is occasionally visible. To change the color scheme, use the Configure IDLE dialog Highlighting tab. The marking of debugger breakpoint lines in the editor and @@ -685,7 +690,7 @@ intended to be the same as executing the same code by the default method, directly with Python in a text-mode system console or terminal window. However, the different interface and operation occasionally affect visible results. For instance, sys.modules starts with more entries, -and threading.activeCount() returns 2 instead of 1.

    +and threading.active_count() returns 2 instead of 1.

    By default, IDLE runs user code in a separate OS process rather than in the user interface process that runs the shell and editor. In the execution process, it replaces sys.stdin, sys.stdout, and sys.stderr @@ -939,7 +944,7 @@ also used for testing.

    • Report a Bug
    • - Show Source
      • @@ -971,7 +976,7 @@ also used for testing.

    • - 3.10.0a6 Documentation » + 3.11.0a0 Documentation »
    • The Python Standard Library »
      • @@ -997,13 +1002,19 @@ also used for testing.

      © Copyright 2001-2021, Python Software Foundation.
      + This page is licensed under the Python Software Foundation License Version 2. +
      + Examples, recipes, and other code in the documentation are additionally licensed under the Zero Clause BSD License. +
      + See History and License for more information. +

      The Python Software Foundation is a non-profit corporation. Please donate.

      - Last updated on Mar 29, 2021. + Last updated on May 11, 2021. Found a bug?
      diff --git a/Lib/idlelib/idle_test/test_colorizer.py b/Lib/idlelib/idle_test/test_colorizer.py index c31c49236ca..498480a74e3 100644 --- a/Lib/idlelib/idle_test/test_colorizer.py +++ b/Lib/idlelib/idle_test/test_colorizer.py @@ -1,11 +1,12 @@ -"Test colorizer, coverage 93%." - +"Test colorizer, coverage 99%." from idlelib import colorizer from test.support import requires import unittest from unittest import mock +from .tkinter_testing_utils import run_in_tk_mainloop from functools import partial +import textwrap from tkinter import Tk, Text from idlelib import config from idlelib.percolator import Percolator @@ -19,15 +20,38 @@ testcfg = { 'extensions': config.IdleUserConfParser(''), } -source = ( - "if True: int ('1') # keyword, builtin, string, comment\n" - "elif False: print(0) # 'string' in comment\n" - "else: float(None) # if in comment\n" - "if iF + If + IF: 'keyword matching must respect case'\n" - "if'': x or'' # valid string-keyword no-space combinations\n" - "async def f(): await g()\n" - "'x', '''x''', \"x\", \"\"\"x\"\"\"\n" - ) +source = textwrap.dedent("""\ + if True: int ('1') # keyword, builtin, string, comment + elif False: print(0) # 'string' in comment + else: float(None) # if in comment + if iF + If + IF: 'keyword matching must respect case' + if'': x or'' # valid keyword-string no-space combinations + async def f(): await g() + # Strings should be entirely colored, including quotes. + 'x', '''x''', "x", \"""x\""" + 'abc\\ + def' + '''abc\\ + def''' + # All valid prefixes for unicode and byte strings should be colored. + r'x', u'x', R'x', U'x', f'x', F'x' + fr'x', Fr'x', fR'x', FR'x', rf'x', rF'x', Rf'x', RF'x' + b'x',B'x', br'x',Br'x',bR'x',BR'x', rb'x', rB'x',Rb'x',RB'x' + # Invalid combinations of legal characters should be half colored. + ur'x', ru'x', uf'x', fu'x', UR'x', ufr'x', rfu'x', xf'x', fx'x' + match point: + case (x, 0) as _: + print(f"X={x}") + case [_, [_], "_", + _]: + pass + case _ if ("a" if _ else set()): pass + case _: + raise ValueError("Not a point _") + ''' + case _:''' + "match x:" + """) def setUpModule(): @@ -107,7 +131,7 @@ class ColorDelegatorInstantiationTest(unittest.TestCase): requires('gui') root = cls.root = Tk() root.withdraw() - text = cls.text = Text(root) + cls.text = Text(root) @classmethod def tearDownClass(cls): @@ -152,7 +176,7 @@ class ColorDelegatorTest(unittest.TestCase): @classmethod def tearDownClass(cls): - cls.percolator.redir.close() + cls.percolator.close() del cls.percolator, cls.text cls.root.update_idletasks() cls.root.destroy() @@ -364,8 +388,21 @@ class ColorDelegatorTest(unittest.TestCase): ('4.0', ('KEYWORD',)), ('4.3', ()), ('4.6', ()), ('5.2', ('STRING',)), ('5.8', ('KEYWORD',)), ('5.10', ('STRING',)), ('6.0', ('KEYWORD',)), ('6.10', ('DEFINITION',)), ('6.11', ()), - ('7.0', ('STRING',)), ('7.4', ()), ('7.5', ('STRING',)), - ('7.12', ()), ('7.14', ('STRING',)), + ('8.0', ('STRING',)), ('8.4', ()), ('8.5', ('STRING',)), + ('8.12', ()), ('8.14', ('STRING',)), + ('19.0', ('KEYWORD',)), + ('20.4', ('KEYWORD',)), ('20.16', ('KEYWORD',)),# ('20.19', ('KEYWORD',)), + #('22.4', ('KEYWORD',)), ('22.10', ('KEYWORD',)), ('22.14', ('KEYWORD',)), ('22.19', ('STRING',)), + #('23.12', ('KEYWORD',)), + ('24.8', ('KEYWORD',)), + ('25.4', ('KEYWORD',)), ('25.9', ('KEYWORD',)), + ('25.11', ('KEYWORD',)), ('25.15', ('STRING',)), + ('25.19', ('KEYWORD',)), ('25.22', ()), + ('25.24', ('KEYWORD',)), ('25.29', ('BUILTIN',)), ('25.37', ('KEYWORD',)), + ('26.4', ('KEYWORD',)), ('26.9', ('KEYWORD',)),# ('26.11', ('KEYWORD',)), ('26.14', (),), + ('27.25', ('STRING',)), ('27.38', ('STRING',)), + ('29.0', ('STRING',)), + ('30.1', ('STRING',)), # SYNC at the end of every line. ('1.55', ('SYNC',)), ('2.50', ('SYNC',)), ('3.34', ('SYNC',)), ) @@ -391,11 +428,173 @@ class ColorDelegatorTest(unittest.TestCase): eq(text.tag_nextrange('COMMENT', '2.0'), ('2.22', '2.43')) eq(text.tag_nextrange('SYNC', '2.0'), ('2.43', '3.0')) eq(text.tag_nextrange('STRING', '2.0'), ('4.17', '4.53')) - eq(text.tag_nextrange('STRING', '7.0'), ('7.0', '7.3')) - eq(text.tag_nextrange('STRING', '7.3'), ('7.5', '7.12')) - eq(text.tag_nextrange('STRING', '7.12'), ('7.14', '7.17')) - eq(text.tag_nextrange('STRING', '7.17'), ('7.19', '7.26')) - eq(text.tag_nextrange('SYNC', '7.0'), ('7.26', '9.0')) + eq(text.tag_nextrange('STRING', '8.0'), ('8.0', '8.3')) + eq(text.tag_nextrange('STRING', '8.3'), ('8.5', '8.12')) + eq(text.tag_nextrange('STRING', '8.12'), ('8.14', '8.17')) + eq(text.tag_nextrange('STRING', '8.17'), ('8.19', '8.26')) + eq(text.tag_nextrange('SYNC', '8.0'), ('8.26', '9.0')) + eq(text.tag_nextrange('SYNC', '30.0'), ('30.10', '32.0')) + + def _assert_highlighting(self, source, tag_ranges): + """Check highlighting of a given piece of code. + + This inserts just this code into the Text widget. It will then + check that the resulting highlighting tag ranges exactly match + those described in the given `tag_ranges` dict. + + Note that the irrelevant tags 'sel', 'TODO' and 'SYNC' are + ignored. + """ + text = self.text + + with mock.patch.object(colorizer.ColorDelegator, 'notify_range'): + text.delete('1.0', 'end-1c') + text.insert('insert', source) + text.tag_add('TODO', '1.0', 'end-1c') + self.color.recolorize_main() + + # Make a dict with highlighting tag ranges in the Text widget. + text_tag_ranges = {} + for tag in set(text.tag_names()) - {'sel', 'TODO', 'SYNC'}: + indexes = [rng.string for rng in text.tag_ranges(tag)] + for index_pair in zip(indexes[::2], indexes[1::2]): + text_tag_ranges.setdefault(tag, []).append(index_pair) + + self.assertEqual(text_tag_ranges, tag_ranges) + + with mock.patch.object(colorizer.ColorDelegator, 'notify_range'): + text.delete('1.0', 'end-1c') + + def test_def_statement(self): + # empty def + self._assert_highlighting('def', {'KEYWORD': [('1.0', '1.3')]}) + + # def followed by identifier + self._assert_highlighting('def foo:', {'KEYWORD': [('1.0', '1.3')], + 'DEFINITION': [('1.4', '1.7')]}) + + # def followed by partial identifier + self._assert_highlighting('def fo', {'KEYWORD': [('1.0', '1.3')], + 'DEFINITION': [('1.4', '1.6')]}) + + # def followed by non-keyword + self._assert_highlighting('def ++', {'KEYWORD': [('1.0', '1.3')]}) + + def test_match_soft_keyword(self): + # empty match + self._assert_highlighting('match', {'KEYWORD': [('1.0', '1.5')]}) + + # match followed by partial identifier + self._assert_highlighting('match fo', {'KEYWORD': [('1.0', '1.5')]}) + + # match followed by identifier and colon + self._assert_highlighting('match foo:', {'KEYWORD': [('1.0', '1.5')]}) + + # match followed by keyword + self._assert_highlighting('match and', {'KEYWORD': [('1.6', '1.9')]}) + + # match followed by builtin with keyword prefix + self._assert_highlighting('match int:', {'KEYWORD': [('1.0', '1.5')], + 'BUILTIN': [('1.6', '1.9')]}) + + # match followed by non-text operator + self._assert_highlighting('match^', {}) + self._assert_highlighting('match @', {}) + + # match followed by colon + self._assert_highlighting('match :', {}) + + # match followed by comma + self._assert_highlighting('match\t,', {}) + + # match followed by a lone underscore + self._assert_highlighting('match _:', {'KEYWORD': [('1.0', '1.5')]}) + + def test_case_soft_keyword(self): + # empty case + self._assert_highlighting('case', {'KEYWORD': [('1.0', '1.4')]}) + + # case followed by partial identifier + self._assert_highlighting('case fo', {'KEYWORD': [('1.0', '1.4')]}) + + # case followed by identifier and colon + self._assert_highlighting('case foo:', {'KEYWORD': [('1.0', '1.4')]}) + + # case followed by keyword + self._assert_highlighting('case and', {'KEYWORD': [('1.5', '1.8')]}) + + # case followed by builtin with keyword prefix + self._assert_highlighting('case int:', {'KEYWORD': [('1.0', '1.4')], + 'BUILTIN': [('1.5', '1.8')]}) + + # case followed by non-text operator + self._assert_highlighting('case^', {}) + self._assert_highlighting('case @', {}) + + # case followed by colon + self._assert_highlighting('case :', {}) + + # case followed by comma + self._assert_highlighting('case\t,', {}) + + # case followed by a lone underscore + self._assert_highlighting('case _:', {'KEYWORD': [('1.0', '1.4'), + ('1.5', '1.6')]}) + + def test_long_multiline_string(self): + source = textwrap.dedent('''\ + """a + b + c + d + e""" + ''') + self._assert_highlighting(source, {'STRING': [('1.0', '5.4')]}) + + @run_in_tk_mainloop + def test_incremental_editing(self): + text = self.text + eq = self.assertEqual + + # Simulate typing 'inte'. During this, the highlighting should + # change from normal to keyword to builtin to normal. + text.insert('insert', 'i') + yield + eq(text.tag_nextrange('BUILTIN', '1.0'), ()) + eq(text.tag_nextrange('KEYWORD', '1.0'), ()) + + text.insert('insert', 'n') + yield + eq(text.tag_nextrange('BUILTIN', '1.0'), ()) + eq(text.tag_nextrange('KEYWORD', '1.0'), ('1.0', '1.2')) + + text.insert('insert', 't') + yield + eq(text.tag_nextrange('BUILTIN', '1.0'), ('1.0', '1.3')) + eq(text.tag_nextrange('KEYWORD', '1.0'), ()) + + text.insert('insert', 'e') + yield + eq(text.tag_nextrange('BUILTIN', '1.0'), ()) + eq(text.tag_nextrange('KEYWORD', '1.0'), ()) + + # Simulate deleting three characters from the end of 'inte'. + # During this, the highlighting should change from normal to + # builtin to keyword to normal. + text.delete('insert-1c', 'insert') + yield + eq(text.tag_nextrange('BUILTIN', '1.0'), ('1.0', '1.3')) + eq(text.tag_nextrange('KEYWORD', '1.0'), ()) + + text.delete('insert-1c', 'insert') + yield + eq(text.tag_nextrange('BUILTIN', '1.0'), ()) + eq(text.tag_nextrange('KEYWORD', '1.0'), ('1.0', '1.2')) + + text.delete('insert-1c', 'insert') + yield + eq(text.tag_nextrange('BUILTIN', '1.0'), ()) + eq(text.tag_nextrange('KEYWORD', '1.0'), ()) @mock.patch.object(colorizer.ColorDelegator, 'recolorize') @mock.patch.object(colorizer.ColorDelegator, 'notify_range') diff --git a/Misc/NEWS.d/next/IDLE/2021-05-09-09-02-09.bpo-44010.TaLe9x.rst b/Misc/NEWS.d/next/IDLE/2021-05-09-09-02-09.bpo-44010.TaLe9x.rst new file mode 100644 index 00000000000..becd331f6d7 --- /dev/null +++ b/Misc/NEWS.d/next/IDLE/2021-05-09-09-02-09.bpo-44010.TaLe9x.rst @@ -0,0 +1,5 @@ +Highlight the new :ref:`match ` statement's +:ref:`soft keywords `: :keyword:`match`, +:keyword:`case `, and :keyword:`_ `. +However, this highlighting is not perfect and will be incorrect in some +rare cases, including some ``_``-s in ``case`` patterns.