bug#42841: 28.0.50; [ruby-mode] ruby-{beginning,end}-of-block doesn't work as is exepected if arguments of method is divided into multi line

[Yasuhiro KIMURA <yasu@utahime.org>]

ruby-{beginning,end}-of-block doesn't work as is exepected if
arguments of method is divided into multi line. Following is a sample
code to reproduce the issue.

----------------------------------------------------------------------
0001: class A
0002:   def foo
0003:     puts("aaa", "bbb")
0004:   end
0005: end
0006:
0007: class B
0008:   def foo
0009:     puts("aaa",
0010:          "bbb")
0011:   end
0012: end
----------------------------------------------------------------------

At first let me assume point is on line 1 column 1. If I type 'C-M-n'
in this situmation, then point moves to line 5 column 1. And if I type
'C-M-p' then point moves back to line 1 column 1. This is just
expected behavior.

Next let me assume point is on line 7 column 1 and I type 'C-M-n'. The
expected behavior is that point moves to line 12 column 1. But what
really happens is that point moves to line 10 column 1 and following
error message is displayed in minibuffer.

Wrong type argument: number-or-marker-p, nil


In GNU Emacs 28.0.50 (build 1, x86_64-w64-mingw32)
 of 2020-08-13 built on ROLLING
Repository revision: d089c4fbfc8be432dc3015a99b4044dab0a0de97
Repository branch: master
Windowing system distributor 'Microsoft Corp.', version 10.0.18363
System Description: Microsoft Windows 10 Enterprise (v10.0.1909.18363.1016)

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