fix: subst not respecting fn and case binds

1 files changed, 29 insertions, 0 deletions

diff --git a/src/sexp/subst.rs b/src/sexp/subst.rs
index 4cfa48d..d09732f 100644
--- a/src/sexp/subst.rs
+++ b/src/sexp/subst.rs
@@ -23,6 +23,35 @@ impl SExp {
                         return SCons(a, b);
                     }
                 }
+		if scons(a.clone(), b.clone()).is_fun() {
+		    let arglist = b.clone().parts()[0].clone();
+		    let arglist = arglist.parts().into_iter().map(|exp| match exp {
+			Atom(Var(s)) => s,
+			_ => todo!(),
+		    }).collect::<Vec<String>>();
+		    if arglist.contains(&name.to_string()) {
+			return SCons(a, b);
+		    }
+		}
+		if let Some((scrut, pavec)) = scons(a.clone(), b.clone())
+		    .get_case_scrut_pats_and_arms()
+		{
+		    let scrut = scrut.subst(name, value);
+		    let mut res = vec![];
+		    for (pat, arm) in pavec {
+			if pat
+			    .get_vars_bound_by_pattern()
+			    .contains(&name.to_string())
+			{
+			    res.push(scons(pat, arm));
+			}
+			else
+			{
+			    res.push(scons(pat, arm.subst(name, value)));
+			}
+		    }
+		    return SExp::back_to_case(scrut, res);
+		}
                 scons((*a).subst(name, value), (*b).subst(name, value))
             },
             Atom(Var(x)) if x == name => value.clone(),