[ruby-core:124027] [Ruby Bug#21758] Prism fails to parse heredoc within %Q literal split by another heredoc

4 Dec 2025


      Issue #21758 has been updated by Earlopain (Earlopain _).


https://github.com/ruby/prism/pull/3780

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Bug #21758: Prism fails to parse heredoc within %Q literal split by another heredoc
https://bugs.ruby-lang.org/issues/21758#change-115458

* Author: tompng (tomoya ishida)
* Status: Open
* Assignee: prism
* ruby -v: ruby 4.0.0dev (2025-12-02T16:20:43Z master c06c2203ed) +PRISM [x86_64-linux]
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
----------------------------------------
Prism fails to parse this code
~~~ruby
<<A; %Q
A
#{<<B}
B
~~~

Parse error:
~~~
a.rb:4: syntax error found (SyntaxError)
  2 | A
  3 | #{<<B}
...
4 | B
    | ^ unexpected constant, expecting end-of-input

`B` at line 4 appears twice in lex result:
~~~ruby
Prism.lex('&lt;&lt;A; %Q
A
#{&lt;&lt;B}
B
').value
#=> 
[[HEREDOC_START(1,0)-(1,3)("&lt;&lt;A"), 1],
 [HEREDOC_END(2,0)-(3,0)("A\n"), 2],
 [SEMICOLON(1,3)-(1,4)(";"), 1],
 [STRING_BEGIN(1,5)-(2,0)("%Q\n"), 1],
 [EMBEXPR_BEGIN(3,0)-(3,2)("\#{"), 1],
 [HEREDOC_START(3,2)-(3,5)("&lt;&lt;B"), 1],
 [HEREDOC_END(4,0)-(5,0)("B\n"), 2],   # B\n here
 [EMBEXPR_END(3,5)-(3,6)("}"), 2],
 [STRING_END(3,6)-(4,0)("\n"), 2],
 [CONSTANT(4,0)-(4,1)("B"), 2],        # Same B again here
 [NEWLINE(4,1)-(5,0)("\n"), 1],
 [EOF(4,1)-(5,0)("\n"), 1]]

-- 
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