This has is a nice-to-have for me. Frequently I want to run a specific
test, and end up digging through output to be able to copy-paste the run
line. This uses TIP lines to inject the command into the file when using
AUTOUPDATE.
Note, one of the reasons I want this is because "bazel test
//toolchain/testing:file_test --test_output=all" has been regularly
exceeding bazel's output limit for me (workaround is either opening the
output file or specifying an obscure output limit flag), making it a
little harder for me to get the commands. However, frequently I'm adding
a file and want to iterate on it, so that's really the use case I have
in mind here.
I've been thinking about this since we decided to add placeholders in
the parse tree. This allows a clearer division of work in check
handling, where we were doing work for ExprOpenParen that's only
necessary for tuples (splitting/renaming handle_paren.cpp accordingly).
(Split out of #3410)
Consistently use `ParenExpr` solely for parenthesized single
expressions, and use more syntax-oriented terminology for states and
nodes that might represent either a `ParenExpr` or a tuple literal.