From: "Earlopain (Earlopain _) via ruby-core" <ruby-core@...>
Date: 2025-12-03T12:48:47+00:00
Subject: [ruby-core:124005] [Ruby Bug#21758] Prism fails to parse heredoc within %Q literal split by another heredoc

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


It can be even simpler:

```rb
%Q
#{<<B}
B
```

Lex output similarly contains B twice.

----------------------------------------
Bug #21758: Prism fails to parse heredoc within %Q literal split by another heredoc
https://bugs.ruby-lang.org/issues/21758#change-115435

* Author: tompng (tomoya ishida)
* Status: Open
* 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('<<A; %Q
A
#{<<B}
B
').value
#=> 
[[HEREDOC_START(1,0)-(1,3)("<<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)("<<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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