grammar(tcl, bash): a bare \ row joins the previous command, not the next row #1808

Both the Tcl grammar (vendored, tree-sitter-tcl/) and tree-sitter-bash 0.25.1 (upstream) treat a row holding only a continuation \ as a join with the row before it. They merge two commands into one, where the interpreter runs two. Found auditing PR #1804's tests (#1445).

Tcl

puts a
\
# c

tclsh prints a. The bare row and # c join into one logical line, a comment. The grammar produces one command whose words are a, #, c:

{command} (1,1)-(3,4)
├─ {simple_word} : puts
╰─ {word_list}
   ├─ {simple_word} : a
   ├─ {simple_word} : #
   ╰─ {simple_word} : c

puts a / \ / puts b likewise parses as one puts a puts b command, although tclsh runs both and prints a and b.

Bash

echo a \
          # (empty row)
\
echo b

bash prints a and then b: the empty row ends the first command. tree-sitter-bash parses one command with words a echo b.

Effect

Halstead happens to agree on these shapes, since the operand multiset is the same. loc's bare-row reader (#1445) is right on the row it reads, but the comment it should join is not a comment node here: it is two words of a command.

Pins

tcl_bare_continuation_rows_are_code_or_comment (src/metrics/loc.rs) pins the Tcl loc row with FIXME(#this).

Fix

A grammar change in both cases. For Tcl it is the vendored grammar, regenerated per AGENTS.md "Tree-sitter grammars". For Bash it is an upstream report. Patching around it in a metric would mean re-deriving command boundaries from bytes.