Introduce param falvor

src/grammar/params.rs

@@ -6,35 +6,67 @@ use super::*;
 // fn c(x: i32, ) {}
 // fn d(x: i32, y: ()) {}
 pub(super) fn param_list(p: &mut Parser) {
-    list_(p, true)
+    list_(p, Flavor::Normal)
+}
+
+// test param_list_opt_patterns
+// fn foo<F: FnMut(&mut Foo<'a>)>(){}
+pub(super) fn param_list_opt_patterns(p: &mut Parser) {
+    list_(p, Flavor::OptionalPattern)
 }
 
 pub(super) fn param_list_opt_types(p: &mut Parser) {
-    list_(p, false)
+    list_(p, Flavor::OptionalType)
 }
 
-fn list_(p: &mut Parser, require_types: bool) {
-    assert!(p.at(if require_types { L_PAREN } else { PIPE }));
+#[derive(Clone, Copy, Eq, PartialEq)]
+enum Flavor {
+    OptionalType,
+    OptionalPattern,
+    Normal,
+}
+
+impl Flavor {
+    fn type_required(self) -> bool {
+        match self {
+            Flavor::OptionalType => false,
+            _ => true,
+        }
+    }
+    fn pattern_required(self) -> bool {
+        match self {
+            Flavor::OptionalPattern => false,
+            _ => true,
+        }
+    }
+}
+
+fn list_(p: &mut Parser, flavor: Flavor) {
+    let (bra, ket) = if flavor.type_required() {
+        (L_PAREN, R_PAREN)
+    } else {
+        (PIPE, PIPE)
+    };
+    assert!(p.at(bra));
     let m = p.start();
     p.bump();
-    if require_types {
+    if flavor.type_required() {
         self_param(p);
     }
-    let terminator = if require_types { R_PAREN } else { PIPE };
-    while !p.at(EOF) && !p.at(terminator) {
-        value_parameter(p, require_types);
-        if !p.at(terminator) {
+    while !p.at(EOF) && !p.at(ket) {
+        value_parameter(p, flavor);
+        if !p.at(ket) {
             p.expect(COMMA);
         }
     }
-    p.expect(terminator);
+    p.expect(ket);
     m.complete(p, PARAM_LIST);
 }
 
-fn value_parameter(p: &mut Parser, require_type: bool) {
+fn value_parameter(p: &mut Parser, flavor: Flavor) {
     let m = p.start();
     patterns::pattern(p);
-    if p.at(COLON) || require_type {
+    if p.at(COLON) || flavor.type_required() {
         types::ascription(p)
     }
     m.complete(p, PARAM);