Coverage reports line as uncovered when run.

[jmgurney]

Describe the bug

I have found that apparently coverage reports a continue statement as being uncovered even though it is run/executed.

To Reproduce

1. Python 3.9.13 (main, May 30 2022, 11:25:38) (tested on Python 3.10.4 (main, May 23 2022, 16:05:39) and doesn't reproduce)

-- sys -------------------------------------------------------
               coverage_version: 6.4.2
                coverage_module: /private/tmp/cv/p/lib/python3.9/site-packages/coverage/__init__.py
                         tracer: -none-
                        CTracer: available
           plugins.file_tracers: -none-
            plugins.configurers: -none-
      plugins.context_switchers: -none-
              configs_attempted: .coveragerc
                                 setup.cfg
                                 tox.ini
                                 pyproject.toml
                   configs_read: -none-
                    config_file: None
                config_contents: -none-
                      data_file: -none-
                         python: 3.9.13 (main, May 30 2022, 11:25:38) [Clang 13.0.0 (clang-1300.0.29.30)]
                       platform: macOS-12.4-x86_64-i386-64bit
                 implementation: CPython
                     executable: /private/tmp/cv/p/bin/python
                   def_encoding: utf-8
                    fs_encoding: utf-8
                            pid: 29182
                            cwd: /private/tmp/cv
                           path: /private/tmp/cv
                                 /opt/local/Library/Frameworks/Python.framework/Versions/3.9/lib/python39.zip
                                 /opt/local/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9
                                 /opt/local/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/lib-dynload
                                 /private/tmp/cv/p/lib/python3.9/site-packages
                    environment: HOME = /Users/jmg
                   command_line: /private/tmp/cv/p/lib/python3.9/site-packages/coverage/__main__.py debug sys
                sqlite3_version: 2.6.0
         sqlite3_sqlite_version: 3.38.5
             sqlite3_temp_store: 0
        sqlite3_compile_options: ATOMIC_INTRINSICS=1, COMPILER=clang-13.0.0, DEFAULT_AUTOVACUUM,
                                 DEFAULT_CACHE_SIZE=-2000, DEFAULT_FILE_FORMAT=4,
                                 DEFAULT_JOURNAL_SIZE_LIMIT=-1, DEFAULT_MMAP_SIZE=0, DEFAULT_PAGE_SIZE=4096,
                                 DEFAULT_PCACHE_INITSZ=20, DEFAULT_RECURSIVE_TRIGGERS,
                                 DEFAULT_SECTOR_SIZE=4096, DEFAULT_SYNCHRONOUS=2,
                                 DEFAULT_WAL_AUTOCHECKPOINT=1000, DEFAULT_WAL_SYNCHRONOUS=2,
                                 DEFAULT_WORKER_THREADS=0, DISABLE_INTRINSIC, ENABLE_COLUMN_METADATA,
                                 ENABLE_FTS3, ENABLE_FTS3_PARENTHESIS, ENABLE_FTS4, ENABLE_FTS5,
                                 ENABLE_GEOPOLY, ENABLE_MATH_FUNCTIONS, ENABLE_RTREE, ENABLE_STAT4,
                                 ENABLE_UNLOCK_NOTIFY, MALLOC_SOFT_LIMIT=1024, MAX_ATTACHED=10,
                                 MAX_COLUMN=2000, MAX_COMPOUND_SELECT=500, MAX_DEFAULT_PAGE_SIZE=8192,
                                 MAX_EXPR_DEPTH=1000, MAX_FUNCTION_ARG=127, MAX_LENGTH=1000000000,
                                 MAX_LIKE_PATTERN_LENGTH=50000, MAX_MMAP_SIZE=0x7fff0000,
                                 MAX_PAGE_COUNT=1073741823, MAX_PAGE_SIZE=65536, MAX_SQL_LENGTH=1000000000,
                                 MAX_TRIGGER_DEPTH=1000, MAX_VARIABLE_NUMBER=32766, MAX_VDBE_OP=250000000,
                                 MAX_WORKER_THREADS=8, MUTEX_PTHREADS, SECURE_DELETE, SOUNDEX,
                                 SYSTEM_MALLOC, TEMP_STORE=1, THREADSAFE=1

coverage==6.4.2

1. What code shows the problem?

for i in ['a', 'b', 'c']:
	if i == 'a':
		print('d')
	elif i == 'b':
		print('e')
	elif i == 'c':
		print('f')
	else: # pragma: no cover
		raise ValueError('unhnadled')

	continue

	raise Exception('an exception')

1. What commands did you run?

python -m coverage run t.py
python -m coverage report -m

Expected behavior

I expect that the report only shows that line 13 is uncovered, but line 11 should be covered as it is the continue that prevents line 13 from running.

Additional context
Add any other context about the problem here.

[nedbat]

This is because jumps to jumps are often optimized away:

% python3.9 -m dis bug1432.py
  1           0 LOAD_CONST               0 (('a', 'b', 'c'))
              2 GET_ITER
        >>    4 FOR_ITER                76 (to 82)
              6 STORE_NAME               0 (i)

  2           8 LOAD_NAME                0 (i)
             10 LOAD_CONST               1 ('a')
             12 COMPARE_OP               2 (==)
             14 POP_JUMP_IF_FALSE       26

  3          16 LOAD_NAME                1 (print)
             18 LOAD_CONST               2 ('d')
             20 CALL_FUNCTION            1
             22 POP_TOP
             24 JUMP_ABSOLUTE            4

  4     >>   26 LOAD_NAME                0 (i)
             28 LOAD_CONST               3 ('b')
             30 COMPARE_OP               2 (==)
             32 POP_JUMP_IF_FALSE       44

  5          34 LOAD_NAME                1 (print)
             36 LOAD_CONST               4 ('e')
             38 CALL_FUNCTION            1
             40 POP_TOP
             42 JUMP_ABSOLUTE            4

  6     >>   44 LOAD_NAME                0 (i)
             46 LOAD_CONST               5 ('c')
             48 COMPARE_OP               2 (==)
             50 POP_JUMP_IF_FALSE       62

  7          52 LOAD_NAME                1 (print)
             54 LOAD_CONST               6 ('f')
             56 CALL_FUNCTION            1
             58 POP_TOP
             60 JUMP_ABSOLUTE            4

  9     >>   62 LOAD_NAME                2 (ValueError)
             64 LOAD_CONST               7 ('unhnadled')
             66 CALL_FUNCTION            1
             68 RAISE_VARARGS            1

 11          70 JUMP_ABSOLUTE            4

 13          72 LOAD_NAME                3 (Exception)
             74 LOAD_CONST               8 ('an exception')
             76 CALL_FUNCTION            1
             78 RAISE_VARARGS            1
             80 JUMP_ABSOLUTE            4
        >>   82 LOAD_CONST               9 (None)
             84 RETURN_VALUE

Notice that nothing jumps to offset 70 (line 11), and all the places that should have be re-written as jumps to offset 4, where line 11 would jump to.

This is being changed in Python 3.10 and later. If you use that version, you should see line 11 covered.

(Duplicate of #198)