Heredoc with more than 300 lines fails to compile on Crystal 0.32.0

[lbguilherme]

The recent Crystal 0.32.0 release includes the new String.interpolation as an alternative codegen for what used to be based on String.build (see #8400).

This is causing issues for me on heredocs with interpolation:

bug = <<-END
x
#{2}
x
x
... 300 more lines with just "x"...
x
x
END

Fails to compile with:

In /tmp/bug.cr:1:5

 1 | bug = <<-END
         ^------------
Error: instantiating 'String.class#interpolation(String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String)'


In /usr/share/crystal/src/string.cr:4536:27

 4536 | def self.interpolation(*values : String)
                                ^
Error: tuple size cannot be greater than 300 (size is 301)

I noticed from reading the parser that heredocs are represented as a StringInterpolation nodes with each line as a individual string in this case. I believe there should be an AST transformation on top of StringInterpolation that will merge any two successive string literals into one, avoiding the issue if I'm just writing a long heredoc. Is this the correct approach to fix this?

[lbguilherme]

dup of #8576