Bug #17530
irb handles << incorrectly with variable as identifier
Description
If you attempt to start a here-document with an identifier that is also a variable, it is interpreted as an append, which makes sense.
That is,
s1 = 'testing'
s2 = 'this'
s2 <<s1
adding text here does not work
s1
Gets an expected error:
testcase.rb:4: syntax error, unexpected local variable or method, expecting '('
adding text here does not work
But irb doesn't know this, and gathers input as though it's a here-document:
irb(main):001:0' s1 = 'testing'
=> "testing"
irb(main):002:0' s2 = 'this'
=> "this"
irb(main):003:0" s2 <<s1
irb(main):004:0" adding text here does not work
irb(main):005:0" s1
Traceback (most recent call last):
3: from /home/centos/.rubies/ruby-3.0.0/bin/irb:23:in `<main>'
2: from /home/centos/.rubies/ruby-3.0.0/bin/irb:23:in `load'
1: from /home/centos/.rubies/ruby-3.0.0/lib/ruby/gems/3.0.0/gems/irb-1.3.0/exe/irb:11:in `<top (required)>'
SyntaxError ((irb):4: syntax error, unexpected local variable or method, expecting '(')
adding text here does not work
^~~~
irb(main):006:0>
Notice the prompt changes on lines 3-5 as though line 3 started a double-quoted here document.
irb should realize that line 3 is appending to s2, not starting a here-document.
This bug is present in the latest irb:
ruby --version
ruby 3.0.0p0 (2020-12-25 revision 95aff21468) [x86_64-linux]
irb --version
irb 1.3.0 (2020-12-25)
It's an odd edge case, but it confused me when I tried to understand the double meaning of <<, so it seemed worth noting.
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