Formatter bug: expecting ), not 'IDENT, bar'

[Blacksmoke16]

Error is similar to #10181, but it still reproduced with #10597 so I'm creating a dedicated issue.

Running the formatter on the code:

 def execute(foo = "foo", bar = "bar")

  pp(foo: foo bar: bar)
end

execute

Produces the error (I ran it with compiled compiler for the backtrace):

from /home/george/dev/git/crystal/src/compiler/crystal/tools/formatter.cr:5022:9 in 'check'
from /home/george/dev/git/crystal/src/compiler/crystal/tools/formatter.cr:2880:9 in 'finish_args'
from /home/george/dev/git/crystal/src/compiler/crystal/tools/formatter.cr:2721:9 in 'visit'
from /home/george/dev/git/crystal/src/compiler/crystal/syntax/visitor.cr:27:12 in 'accept'
from /home/george/dev/git/crystal/src/compiler/crystal/syntax/visitor.cr:20:7 in 'accept'
from /home/george/dev/git/crystal/src/compiler/crystal/tools/formatter.cr:4684:24 in 'indent'
from /home/george/dev/git/crystal/src/compiler/crystal/tools/formatter.cr:4708:7 in 'write_indent'
from /home/george/dev/git/crystal/src/compiler/crystal/tools/formatter.cr:1397:13 in 'format_nested'
from /home/george/dev/git/crystal/src/compiler/crystal/tools/formatter.cr:1388:5 in 'format_nested:write_end_line'
from /home/george/dev/git/crystal/src/compiler/crystal/tools/formatter.cr:1424:7 in 'format_nested_with_end'
from /home/george/dev/git/crystal/src/compiler/crystal/tools/formatter.cr:1409:5 in 'format_nested_with_end'
from /home/george/dev/git/crystal/src/compiler/crystal/tools/formatter.cr:1493:9 in 'visit'
from /home/george/dev/git/crystal/src/compiler/crystal/syntax/visitor.cr:27:12 in 'accept'
from /home/george/dev/git/crystal/src/compiler/crystal/syntax/visitor.cr:20:7 in 'accept'
from /home/george/dev/git/crystal/src/compiler/crystal/tools/formatter.cr:4684:24 in 'indent'
from /home/george/dev/git/crystal/src/compiler/crystal/tools/formatter.cr:262:11 in 'visit'
from /home/george/dev/git/crystal/src/compiler/crystal/syntax/visitor.cr:27:12 in 'accept'
from /home/george/dev/git/crystal/src/compiler/crystal/tools/formatter.cr:16:7 in 'format'
from /home/george/dev/git/crystal/src/compiler/crystal/tools/formatter.cr:5:5 in 'format'
from /home/george/dev/git/crystal/src/compiler/crystal/command/format.cr:159:7 in 'format'
from /home/george/dev/git/crystal/src/compiler/crystal/command/format.cr:127:16 in 'format_source'
from /home/george/dev/git/crystal/src/compiler/crystal/command/format.cr:123:7 in 'format_file'
from /home/george/dev/git/crystal/src/compiler/crystal/command/format.cr:110:11 in 'format_file_or_directory'
from /home/george/dev/git/crystal/src/compiler/crystal/command/format.cr:103:9 in 'format_many'
from /home/george/dev/git/crystal/src/compiler/crystal/command/format.cr:92:9 in 'run'
from /home/george/dev/git/crystal/src/compiler/crystal/command/format.cr:53:5 in 'format'
from /home/george/dev/git/crystal/src/compiler/crystal/command.cr:160:7 in 'tool'
from /home/george/dev/git/crystal/src/compiler/crystal/command.cr:108:7 in 'run'
from /home/george/dev/git/crystal/src/compiler/crystal/command.cr:49:5 in 'run'
from /home/george/dev/git/crystal/src/compiler/crystal/command.cr:48:3 in 'run'
from /home/george/dev/git/crystal/src/compiler/crystal.cr:11:1 in '__crystal_main'
from /home/george/dev/git/crystal/src/crystal/main.cr:110:5 in 'main_user_code'
from /home/george/dev/git/crystal/src/crystal/main.cr:96:7 in 'main'
from /home/george/dev/git/crystal/src/crystal/main.cr:119:3 in 'main'
from __libc_start_main
from _start
from ???

What's also interesting is that the example code actually compiles fine.

[straight-shoota]

the example code actually compiles fine.

😲

Interestingly, it prints {foo: "foo"}. The bar part is entirely vanished.

The same happens with a named tuple literal:

foo = "foo"
{foo: foo bar: foo} # => {foo: "foo"}

[straight-shoota]

The fact that the example compiles reveales a more general parser bug: A call is incorrectly identified as reading from a local variable if such exists, even with a named argument (and no parenthesis).

The following code is a minimal reproduction:

foo = 1
foo b: 1

The parser entirely skips the named argument. And that actually causes the formatter to error because it traverses the AST and source input in sync and that doesn't line up when the AST presents a var but the source moves on to the named argument.

Fix is in #10842