I found another mistake I made. In the two rules that use <before...> and <rest>, that <before...> should be used whenever the rule matches the remainder of the expr.
In particular, for symbols to work as positional args whenever there isn't a keyword, the symbol rule needs to fall back to (<before...> <str> ... <rest>), reflecting the original location of the symbol in the pattern. I just had it falling back to (<str> ... <rest>) for some reason.
---
(<before...> <k> <v> ... <rest>)
; where <before...> is any number of non-keyword, non-symbol
; elements; <k> is a keyword; and <rest> could be anything,
; especially an improper list
This pattern treats the current expr as an unevaluated improper list, looking for the first occurrence of <k> with another element after it (which we will refer to as the value expr).
If the keyword binding is found: Matches <v> against the value expr. Matches <rest> against an alteration of the current expr, changed to remove the keyword and the value expr. Uses all variable bindings produced by <v> and <rest>, preferring the bindings in <rest>.
If the keyword binding is not found: Matches the pattern <rest> against the entire expr. Uses those variable bindings.
(<before...> <s> ... <rest>)
; where <before...> is any number of non-keyword, non-symbol
; elements; <s> is a symbol; and <rest> could be anything,
; especially an improper list
Let <k> be the keyword with the same name as the symbol <s>, and let <str> be this name as a string.
This pattern treats the current expr as an unevaluated improper list, looking for the first occurrence of <k> with another element after it (which we will refer to as the value expr).
If the keyword binding is found: Matches <str> against the value expr. Matches <rest> against an alteration of the current expr, changed to remove the keyword and the value expr. Uses all variable bindings produced by <str> and <rest>, preferring the bindings in <rest>.
If the keyword binding is not found: Matches the pattern (<str> ... <rest>) against the entire expr. Uses those variable bindings.
---
After this fix:
---
(<before...> <k> <v> ... <rest>)
; where <before...> is any number of non-keyword, non-symbol
; elements; <k> is a keyword; and <rest> could be anything,
; especially an improper list
This pattern treats the current expr as an unevaluated improper list, looking for the first occurrence of <k> with another element after it (which we will refer to as the value expr).
If the keyword binding is found: Matches <v> against the value expr. Matches the pattern (<before...> ... <rest>) against an alteration of the current expr, changed to remove the keyword and the value expr. Uses all variable bindings produced by <v> and (<before...> ... <rest>), preferring the bindings in the latter.
If the keyword binding is not found: Matches the pattern (<before...> ... <rest>) against the entire expr. Uses those variable bindings.
(<before...> <s> ... <rest>)
; where <before...> is any number of non-keyword, non-symbol
; elements; <s> is a symbol; and <rest> could be anything,
; especially an improper list
Let <k> be the keyword with the same name as the symbol <s>, and let <str> be this name as a string.
This pattern treats the current expr as an unevaluated improper list, looking for the first occurrence of <k> with another element after it (which we will refer to as the value expr).
If the keyword binding is found: Matches <str> against the value expr. Matches the pattern (<before...> ... <rest>) against an alteration of the current expr, changed to remove the keyword and the value expr. Uses all variable bindings produced by <str> and (<before...> ... <rest>), preferring the bindings in the latter.
If the keyword binding is not found: Matches the pattern (<before...> <str> ... <rest>) against the entire expr. Uses those variable bindings.
