Nim fails to parsecommand invocation syntax in block as part of expression list

[tersec]

Description

# stmt -> complexOrSimpleStmt -> simpleStmt -> discardStmt
# where "discardStmt = 'discard' optInd expr?", and optInd
# is "optInd = COMMENT? IND?" so matches nothing here.
#
# Then all the non-simpleExpr cases of expr require some non-'(' initial
# token so expr -> simpleExpr, which scans through the precedence order,
# and eventually reaches primary -> identOrLiteral -> tupleConstr:
#
# tupleConstr = '(' optInd (exprColonEqExpr comma?)* optPar ')'
#
# Still no optInd, so exprColonEqExpr = expr (':'|'=' expr)?
#
# expr matches "ifExpr = 'if' condExpr" and "literal = | INT_LIT",
# which is '0'.
#
# https://nim-lang.org/docs/manual.html#procedures-command-invocation-syntax
# "Routines can be invoked without the () if the call is syntactically a
# statement. This command invocation syntax also works for expressions, but
# then only a single argument may follow. This restriction means
# `echo f 1, f 2` is parsed as `echo(f(1), f(2))` and not as
# `echo(f(1, f(2)))`.
#
# is satisfied here. `f()` takes one argument and is used with one argument.

proc f(x: int): int = 0

discard (
  if true:
    f 0
  else:
    f 0,
  1)

f(try:
    0
  finally:
    int 0,
  0)

shows a similar issue and basically analogous parsing/grammar.

f(try:
    0
  except CatchableError:
    int 0,
  0)

does as well.

Nim Version

Current devel

Nim Compiler Version 1.9.3 [Linux: amd64]
Compiled at 2023-06-08
Copyright (c) 2006-2023 by Andreas Rumpf

git hash: ea91cfb3050bac5c808ed8ab08e12cd33f1dc8ff
active boot switches: -d:release

Nim Compiler Version 1.6.12 [Linux: amd64]
Compiled at 2023-06-06
Copyright (c) 2006-2023 by Andreas Rumpf

git hash: 1aa9273640c0c51486cf3a7b67282fe58f360e91
active boot switches: -d:release

Current Output

ifelse.nim(32, 3) Error: invalid indentation

Similar errors for other variations (try/finally, try/except, et cetera)

Expected Output

Successful compilation

Possible Solution

No response

Additional Information

No response

[metagn]

Some effort related to this was in #20994 (these diffs: terminate command parsing on unindent, test for successful parsing of a similar case). Maybe on p.tok.indent >= 0 and p.tok.indent < baseIndent, it should return and not break. There might be a deeper problem though.

[metagn]

As noted in #21655, condExpr does not actually parse expr, it parses stmt, so it attempts to parse f 0, 1 which consumes the comma but quits after the comma due to the unindent