Allow multiline if then else

[JaroslavTulach]

Pull Request Description

• Allow multi line if then else like

if a==b then
    action
else
    anotheraction

• fixes Support multi-line if-then-else #6408
• example usage:

Important Notes

• with IfThenElse IR instead of if_then_else function invocation #11365 support
  • we just need to recognize IfThenElse without else branch
  • followed by else application
  • and join them together
• this PR approaches that with few easy steps
  • write a test - done in 936a6ab
  • join IfThen and else together - done in 571f21a
  • adjust the test to ignore nuances - done in ad83d52
  • use this somewhere - done in 7c386a3

Checklist

Please ensure that the following checklist has been satisfied before submitting the PR:

• The documentation has been updated, if necessary.
• All code follows the
  Java,
  Rust
• Unit tests have been written where possible.

[jdunkerley]

If we do a patch release we may need to include this as I expect libs will use it pretty quickly :)

Thank you and @kazcw for enabling this

[JaroslavTulach]

• the 48731d4 commit tries to implement the same idea as has previously been done in TreeToIr
• if 48731d4 gets polished, then 571f21a will not be needed
• right now the Tree::multi_segment_app(all_segments) manual manipulation results in assertion error:

thread 'if_block_else_block' panicked at lib/rust/parser/src/source/span.rs:204:13:
assertion `left == right` failed
  left: Location { utf8: 18, utf16: 18, line: 1, col16: 5 }
 right: Location { utf8: 19, utf16: 19, line: 2, col16: 0 }
stack backtrace:
   0: __rustc::rust_begin_unwind
             at /rustc/1159e78c4747b02ef996e55082b704c09b970588/library/std/src/panicking.rs:697:5
   1: core::panicking::panic_fmt
             at /rustc/1159e78c4747b02ef996e55082b704c09b970588/library/core/src/panicking.rs:75:14
   2: core::panicking::assert_failed_inner
   3: core::panicking::assert_failed
             at /.rustup/toolchains/1.90.0-aarch64-apple-darwin/lib/rustlib/src/rust/library/core/src/panicking.rs:403:5
   4: enso_parser::source::span::Span::concat
             at enso/lib/rust/parser/src/source/span.rs:204:13
   5: <enso_parser::syntax::token::Token<T> as enso_parser::source::span::Builder>::add_to_span
             at enso/lib/rust/parser/src/source/span.rs:339:18
   6: enso_parser::source::span::Span::add
             at enso/lib/rust/parser/src/source/span.rs:179:9
   7: <enso_parser::syntax::tree::MultiSegmentAppSegment as enso_parser::source::span::Builder>::add_to_span
             at enso/lib/rust/parser/src/syntax/tree.rs:822:14
   8: <enso_prelude::data::non_empty_vec::NonEmptyVec<T> as enso_parser::source::span::Builder>::add_to_span::{{closure}}
             at enso/lib/rust/parser/src/source/span.rs:377:53
   9: <core::slice::iter::IterMut<T> as core::iter::traits::iterator::Iterator>::fold
             at /.rustup/toolchains/1.90.0-aarch64-apple-darwin/lib/rustlib/src/rust/library/core/src/slice/iter/macros.rs:255:27
  10: <enso_prelude::data::non_empty_vec::NonEmptyVec<T> as enso_parser::source::span::Builder>::add_to_span
             at enso/lib/rust/parser/src/source/span.rs:377:26
  11: enso_parser::source::span::Span::add
             at enso/lib/rust/parser/src/source/span.rs:179:9
  12: enso_parser::syntax::tree::Tree::multi_segment_app
             at enso/lib/rust/parser/src/source/span.rs:300:63
  13: enso_parser::syntax::statement::compound_lines_maybe_with_tail
             at enso/lib/rust/parser/src/syntax/statement.rs:149:47
  14: enso_parser::syntax::statement::compound_lines_with_tail
             at enso/lib/rust/parser/src/syntax/statement.rs:88:5
  15: enso_parser::syntax::statement::BodyBlockParser::parse_body_block
             at enso/lib/rust/parser/src/syntax/statement.rs:47:26
  16: enso_parser::syntax::tree::block::parse_block
             at enso/lib/rust/parser/src/syntax/tree/block.rs:60:32
  17: <enso_parser::macros::resolver::ResolverState as enso_parser::syntax::expression::consumer::Finish>::finish
             at enso/lib/rust/parser/src/macros/resolver.rs:178:17
  18: <enso_parser::macros::resolver::Resolver as enso_parser::syntax::expression::consumer::Finish>::finish
             at enso/lib/rust/parser/src/macros/resolver.rs:252:23
  19: <enso_parser::lexer::Lexer<Inner> as enso_parser::syntax::expression::consumer::Finish>::finish
             at enso/lib/rust/parser/src/lexer.rs:1403:32
  20: enso_parser::Parser::run
             at enso/lib/rust/parser/src/lib.rs:178:80
  21: enso_parser::Parser::parse_block
             at enso/lib/rust/parser/src/lib.rs:173:14
  22: enso_parser_debug::test::parse_block
             at ./src/test.rs:61:42
  23: parse::if_block_else_block
             at ./tests/parse.rs:33:45
  24: parse::if_block_else_block::{{closure}}
             at ./tests/parse.rs:114:25
  25: core::ops::function::FnOnce::call_once
             at /.rustup/toolchains/1.90.0-aarch64-apple-darwin/lib/rustlib/src/rust/library/core/src/ops/function.rs:253:5
  26: core::ops::function::FnOnce::call_once
             at /rustc/1159e78c4747b02ef996e55082b704c09b970588/library/core/src/ops/function.rs:253:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
test if_block_else_block ... FAILED

• probably some locations aren't quite right yet
• concatenating Trees from multiple lines without including the newline isn't being liked...

[JaroslavTulach]

• Do you have any advice, @kazcw?
• This line panics with stack trace listed here

thread 'if_block_else_block' panicked at lib/rust/parser/src/source/span.rs:204:13:
assertion `left == right` failed
  left: Location { utf8: 18, utf16: 18, line: 1, col16: 5 }
 right: Location { utf8: 19, utf16: 19, line: 2, col16: 0 }```

• As far as I understand, the else_segment MultiSegmentAppSegment does not follow the previous
  • if_then_segments
• What should be the fix?
  • Insert NewLine between the segments somehow?
  • Expand the span of last if_then_segments segment?
  • Change the start of else_segment to directly follow the last if_then_segments segment?
• Thanks in advance for any advice.