`--enable-error-code unreachable` does not enable unreachability analysis, yet neither is it reported as an invalid error code (etc)

[wyattscarpenter]

In my understanding, --enable-error-code unreachable should have the same effect as --warn-unreachable. But, instead, it seems to have no effect, and doesn't even produce an error.

$uvx mypy -c "if False: print('hello')"
Success: no issues found in 1 source file

$uvx mypy -c "if False: print('hello')" --warn-unreachable
<string>:1: error: Statement is unreachable  [unreachable]
Found 1 error in 1 file (checked 1 source file)

$uvx mypy -c "if False: print('hello')" --enable-error-code unreachable
Success: no issues found in 1 source file

$uvx mypy -c "if False: print('hello')" --enable-error-code unreachable --warn-unreachable
<string>:1: error: Statement is unreachable  [unreachable]
Found 1 error in 1 file (checked 1 source file)

$uvx mypy -c "if False: print('hello')" --enable-error-code funnyerrorcodenotreal
usage: mypy [-h] [-v] [-V] [more options; see below]
            [-m MODULE] [-p PACKAGE] [-c PROGRAM_TEXT] [files ...]
mypy: error: Invalid error code(s): funnyerrorcodenotreal

[wyattscarpenter]

Oh, the same thing is true about --warn-redundant-casts. And, I suspect, all error codes and flags like this.

$uvx mypy -c "from typing import cast; cast(int, 1)" --warn-redundant-casts
<string>:1: error: Redundant cast to "int"  [redundant-cast]
Found 1 error in 1 file (checked 1 source file)

$uvx mypy -c "from typing import cast; cast(int, 1)" --enable-error-code redundant-cast
Success: no issues found in 1 source file

If they aren't going to have any effect there should be an error message. (But, really, they should just have an effect!)