doughlang: Preserve errors through entire pipeline

lexer:
- Un-stringify errors
- Reserve more words
- Doc the comments

parser:
- MASSIVE changes to peek, peek_if, next_if, consume_if=>expect.
- Keep track of when EOF is allowable
- TKind is stupidly cheap with >100 niches, so we can fit like 4 of them in a single ParseError lmao
- TODO: make sure EOF/UnexpectedEOF propagation is correct. It seems... Kinda Not correct.
- Add meta-expressions

src/token.rs

@@ -9,6 +9,12 @@ pub struct Token {
     pub span: Span,
 }
 
+impl Token {
+    pub fn kind(&self) -> TKind {
+        self.kind
+    }
+}
+
 #[derive(Clone, Debug)]
 pub enum Lexeme {
     String(String),
@@ -55,7 +61,9 @@ impl std::fmt::Display for Lexeme {
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum TKind {
-    Comment,
+    Comment, // Line or block comment
+    Doc,     // Doc comment
+
     And,
     As,
     Break,
@@ -67,6 +75,7 @@ pub enum TKind {
     Fn,
     For,
     If,
+    Impl,
     In,
     Let,
     Loop,
@@ -76,6 +85,7 @@ pub enum TKind {
     Or,
     Public,
     Return,
+    Static,
     Struct,
     True,
     While,