String interpolation: combine contiguous string literals

[asterite]

Fixes #8576

I think this should go in 0.32.1 because this was an accidental breaking change.

The fix is done at normalization because doing it before breaks the formatter a bit (mainly around string literals that aren't actually string literals, like __FILE__), but this way is fine.

[Sija]

Just as a side-note - it doesn't actually fix #8576, it just pushes the limit bit more but the root cause is still there.

[asterite]

@Sija I just don't think a heredoc with ~150 things interpolated in them is realistic. We can close that one, and if someone stumbles upon it again with a real code with that many interpolations we can tackle it too.

[vlazar]

The heredoc in issue #8576 seem to have just 1 interpolation inside and many more lines. The use-case was real, a code generation in https://github.com/cubos/sdkgen/blob/master/src/target/java_android.cr

I think it's a rare use-case, but I imagine in some cases having a long source inside heredoc with some interpolations inside would look nicer that splitting generated source into multiple heredocs.

So if there is a 1000 lines long text inside heredoc and a couple of interpolations inside, will it work now with this fix?

[asterite]

Yes, that case will work. The bug was that a string literal was generated for every line, regardless of interpolation. Now the size of the tuple depends on the number of interpolations.

[lbguilherme]

Out of curiosity: Why does the parser generate a string interpolation for every line instead of generating a multi-line string literal?

[asterite]

If I remember correctly the parser will spit out lines because then it needs to realign each of them according to the heredocs indentation. I tried to fix it in the parser, it broke the formatter and so I made the fix later on.

In any case, once this is merged I will maybe send another PR in which constants that refer to strings and appear in string interpolations will be inlined right away, so contiguous merging will still be needed.