represent 4th variant of slots, and disallow empty primary slot names

src/atom/mod.rs

@@ -85,8 +85,9 @@ pub struct SlotName(#[get(method = "name", kind = "deref")] String);
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub enum Slot {
     Wildcard,
-    Equal {
-        primary: Option<SlotName>,
+    Equal,
+    NameEqual {
+        primary: SlotName,
         sub: Option<SlotName>,
     },
     Name {
@@ -592,10 +593,11 @@ impl fmt::Display for Slot {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             Self::Wildcard => write!(f, "*"),
-            Self::Equal { primary, sub } => {
-                if let Some(primary) = primary {
-                    write!(f, "{primary}")?;
+            Self::Equal => {
+                write!(f, "=")
             }
+            Self::NameEqual { primary, sub } => {
+                write!(f, "{primary}")?;
 
                 if let Some(sub) = sub {
                     write!(f, "/{sub}")?;

src/atom/parsers.rs

@@ -210,16 +210,16 @@ impl<'a> Parseable<'a, &'a str> for Slot {
 
     fn parser() -> Self::Parser {
         let wildcard = tag("*").map(|_| Slot::Wildcard);
-        let equals = SlotName::parser()
-            .opt()
+        let equal = tag("=").map(|_| Slot::Equal);
+        let name_equal = SlotName::parser()
             .and(SlotName::parser().preceded_by(tag("/")).opt())
             .followed_by(tag("="))
-            .map(|(primary, sub)| Slot::Equal { primary, sub });
+            .map(|(primary, sub)| Slot::NameEqual { primary, sub });
         let name = SlotName::parser()
             .and(SlotName::parser().preceded_by(tag("/")).opt())
-            .map(|(primary, sub)| Slot::Name { primary, sub });
+            .map(|(primary, sub)| Self::Name { primary, sub });
 
-        wildcard.or(equals).or(name)
+        wildcard.or(equal).or(name_equal).or(name)
     }
 }
 
@@ -585,6 +585,7 @@ mod test {
             "<dev-haskell/wai-3.3:=[]",
             ">=kde-frameworks/kcrash-2.16.0:6*",
             "0-f/merreka+m::k+",
+            "iev-a/h:/n=",
         ];
 
         for atom in atoms {