parser: make Assign an InfixOp instead of expression type

Closes #14

trunk_parser/src/ast.rs

@@ -320,6 +320,7 @@ pub enum InfixOp {
     NotIdentical,
     And,
     Or,
+    Assign,
     AddAssign,
 }
 
@@ -341,6 +342,7 @@ impl From<TokenKind> for InfixOp {
             TokenKind::BangDoubleEquals => Self::NotIdentical,
             TokenKind::BooleanAnd => Self::And,
             TokenKind::BooleanOr => Self::Or,
+            TokenKind::Equals => Self::Assign,
             TokenKind::PlusEquals => Self::AddAssign,
             _ => unreachable!()
         }

trunk_parser/src/parser/mod.rs

@@ -1202,10 +1202,6 @@ fn prefix(op: &TokenKind, rhs: Expression) -> Expression {
 }
 
 fn infix(lhs: Expression, op: TokenKind, rhs: Expression) -> Expression {
-    if op == TokenKind::Equals {
-        return Expression::Assign(Box::new(lhs), Box::new(rhs));
-    }
-
     Expression::Infix(Box::new(lhs), op.into(), Box::new(rhs))
 }
 
@@ -1350,11 +1346,12 @@ mod tests {
     #[test]
     fn array_index_assign() {
         assert_ast("<?php $foo['bar'] = 'baz';", &[
-            expr!(Expression::Assign(
+            expr!(Expression::Infix(
                 Box::new(Expression::ArrayIndex(
                     Box::new(Expression::Variable("foo".into())),
                     Some(Box::new(Expression::ConstantString("bar".into())))
                 )),
+                InfixOp::Assign,
                 Box::new(Expression::ConstantString("baz".into()))
             ))
         ]);