ast: pub patterns, and, since Pat replaced Ty, !(never) patterns.

src/ast.rs

@@ -65,6 +65,8 @@ pub enum Use {
 pub enum Pat {
     /// Matches anything without binding
     Ignore,
+    /// Matches nothing, ever
+    Never,
     /// Matches nothing; used for macro substitution
     MetId(String),
     /// Matches anything, and binds it to a name
@@ -84,6 +86,8 @@ pub enum Pat {
 /// Operators on lists of patterns
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub enum PatOp {
+    /// Changes the visibility mode to "public"
+    Pub,
     /// Changes the binding mode to "mutable"
     Mut,
     /// Matches the dereference of a pointer (`&pat`)
@@ -541,6 +545,7 @@ impl Display for Pat {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
             Self::Ignore => "_".fmt(f),
+            Self::Never => "!".fmt(f),
             Self::Lit(literal) => literal.fmt(f),
             Self::MetId(name) => write!(f, "`{name}"),
             Self::Name(name) => name.fmt(f),
@@ -569,6 +574,7 @@ impl Display for Pat {
 impl Display for PatOp {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         f.write_str(match self {
+            Self::Pub => "pub ",
             Self::Mut => "mut ",
             Self::Ref => "&",
             Self::Rest => "..",