parser: support throw expressions

It's worth noting that a `throw` will always be an expression in the Trunk parser.
PHP-Parser will convert standalone `throw` expressions into a dedicated `throw`
statement for backwards-compatibility reasons.

trunk_lexer/src/lexer.rs

@@ -749,6 +749,7 @@ fn identifier_to_keyword(ident: &str) -> Option<TokenKind> {
         "return" => TokenKind::Return,
         "static" => TokenKind::Static,
         "switch" => TokenKind::Switch,
+        "throw" => TokenKind::Throw,
         "trait" => TokenKind::Trait,
         "true" | "TRUE" => TokenKind::True,
         "try" => TokenKind::Try,

trunk_lexer/src/token.rs

@@ -125,6 +125,7 @@ pub enum TokenKind {
     Slash,
     Static,
     Switch,
+    Throw,
     Trait,
     TripleEquals,
     True,
@@ -261,6 +262,7 @@ impl Display for TokenKind {
             Self::Slash => "/",
             Self::Static => "static",
             Self::Switch => "switch",
+            Self::Throw => "throw",
             Self::Trait => "trait",
             Self::TripleEquals => "===",
             Self::True => "true",

trunk_parser/src/ast.rs

@@ -394,6 +394,9 @@ pub enum Expression {
         condition: Box<Self>,
         arms: Vec<MatchArm>,
     },
+    Throw {
+        value: Box<Expression>,
+    },
 }
 
 #[derive(Debug, PartialEq, Clone, Serialize)]

trunk_parser/src/parser/mod.rs

@@ -959,6 +959,13 @@ impl Parser {
         self.skip_comments();
 
         let mut lhs = match &self.current.kind {
+            TokenKind::Throw => {
+                self.next();
+
+                let value = self.expression(0)?;
+
+                Expression::Throw { value: Box::new(value) }
+            },
             TokenKind::Clone => {
                 self.next();