diff --git a/crates/oyster_parser/src/parser.rs b/crates/oyster_parser/src/parser.rs
index bbf06bc..34756cd 100644
--- a/crates/oyster_parser/src/parser.rs
+++ b/crates/oyster_parser/src/parser.rs
@@ -144,90 +144,88 @@ impl Iterator for Parser<'_> {
             };
         }
 
-        use TokenKind::*;
-
         if let Some(ev) = self.buffer.take() {
             return Some(ev);
         }
 
-        match self.stack.last() {
-            None => None,
-            Some(nt) => match nt {
-                // XXX: unify Program and CommandSubstitution to avoid duplication
-                NodeKind::Program => match self.lookahead.kind {
-                    Whitespace => leaf!(Whitespace),
-                    Newlines => leaf!(Newlines),
-                    Semicolon => leaf!(Semicolon),
-                    Comment => leaf!(Comment),
-                    PlainText | DoubleQuote | OpeningParenthesis | EscapedChar => call!(Pipeline),
-                    Pipe => error!(UnexpectedPipe),
-                    ClosingParenthesis => error!(UnexpectedClosingParenthesis),
-                    Eof => chain!(None, ret!()), // return silently
-                },
-                NodeKind::CommandSubstitution => match self.lookahead.kind {
-                    Whitespace => leaf!(Whitespace),
-                    Newlines => leaf!(Newlines),
-                    Semicolon => leaf!(Semicolon),
-                    Comment => leaf!(Comment),
-                    PlainText | DoubleQuote | OpeningParenthesis | EscapedChar => call!(Pipeline),
-                    ClosingParenthesis => match self.stack.get(self.stack.len() - 2) {
-                        Some(&NodeKind::DQuotedString) => {
-                            chain_buf!(leaf!(ClosingParenthesis, String), ret!())
-                        }
-                        _ => chain_buf!(leaf!(ClosingParenthesis, Command), ret!()),
-                    },
-                    Pipe => error!(UnexpectedPipe),
-                    Eof => chain_buf!(error!(UnexpectedEof), ret!()),
-                },
-                NodeKind::Pipeline => match self.lookahead.kind {
-                    Whitespace => leaf!(Whitespace),
-                    Comment => leaf!(Comment),
-                    Pipe => chain!(leaf!(Pipe), call!(PipelineCont)),
-                    PlainText | DoubleQuote | OpeningParenthesis | EscapedChar => call!(Command),
-                    Newlines | Semicolon | ClosingParenthesis | Eof => ret!(),
-                },
-                NodeKind::PipelineCont => match self.lookahead.kind {
-                    Whitespace => leaf!(Whitespace),
-                    Newlines => leaf!(Newlines),
-                    Comment => leaf!(Comment),
-                    PlainText | DoubleQuote | OpeningParenthesis | EscapedChar => {
-                        chain!(call!(Command), ret!())
+        use TokenKind::*;
+
+        match self.stack.last()? {
+            // XXX: unify Program and CommandSubstitution to avoid duplication
+            NodeKind::Program => match self.lookahead.kind {
+                Whitespace => leaf!(Whitespace),
+                Newlines => leaf!(Newlines),
+                Semicolon => leaf!(Semicolon),
+                Comment => leaf!(Comment),
+                PlainText | DoubleQuote | OpeningParenthesis | EscapedChar => call!(Pipeline),
+                Pipe => error!(UnexpectedPipe),
+                ClosingParenthesis => error!(UnexpectedClosingParenthesis),
+                Eof => chain!(None, ret!()), // return silently
+            },
+            NodeKind::CommandSubstitution => match self.lookahead.kind {
+                Whitespace => leaf!(Whitespace),
+                Newlines => leaf!(Newlines),
+                Semicolon => leaf!(Semicolon),
+                Comment => leaf!(Comment),
+                PlainText | DoubleQuote | OpeningParenthesis | EscapedChar => call!(Pipeline),
+                ClosingParenthesis => match self.stack.get(self.stack.len() - 2) {
+                    Some(&NodeKind::DQuotedString) => {
+                        chain_buf!(leaf!(ClosingParenthesis, String), ret!())
                     }
-                    Semicolon => chain_buf!(chain!(error!(UnexpectedSemicolon), ret!()), ret!()),
-                    Pipe => chain!(error!(UnexpectedPipe), ret!()),
-                    ClosingParenthesis => chain!(error!(UnexpectedClosingParenthesis), ret!()),
-                    Eof => chain!(error!(UnexpectedEof), ret!()),
-                },
-                NodeKind::Command => match self.lookahead.kind {
-                    Whitespace => leaf!(Whitespace),
-                    Comment => leaf!(Comment),
-                    PlainText | DoubleQuote | OpeningParenthesis | EscapedChar => call!(Word),
-                    Newlines | Semicolon | Pipe | ClosingParenthesis | Eof => ret!(),
-                },
-                NodeKind::Word => match self.lookahead.kind {
-                    PlainText => leaf!(PlainText),
-                    EscapedChar => leaf!(EscapedChar),
-                    DoubleQuote => chain_buf!(call!(DQuotedString), leaf!(DoubleQuote, String)),
-                    OpeningParenthesis => {
-                        chain_buf!(call!(CommandSubstitution), leaf!(OpeningParenthesis))
-                    }
-                    Comment | Whitespace | Newlines | Semicolon | Pipe | ClosingParenthesis
-                    | Eof => ret!(),
-                },
-                NodeKind::DQuotedString => match self.lookahead.kind {
-                    PlainText => leaf!(PlainText, String),
-                    EscapedChar => leaf!(EscapedChar, String),
-                    DoubleQuote => chain_buf!(leaf!(DoubleQuote, Command), ret!()),
-                    OpeningParenthesis => chain_buf!(
-                        call!(CommandSubstitution),
-                        leaf!(OpeningParenthesis, Command)
-                    ),
-                    ClosingParenthesis => error!(UnexpectedClosingParenthesis, String),
-                    Eof => chain_buf!(error!(UnexpectedEof, Command), ret!()),
-                    _ => unreachable!(),
+                    _ => chain_buf!(leaf!(ClosingParenthesis, Command), ret!()),
                 },
+                Pipe => error!(UnexpectedPipe),
+                Eof => chain_buf!(error!(UnexpectedEof), ret!()),
+            },
+            NodeKind::Pipeline => match self.lookahead.kind {
+                Whitespace => leaf!(Whitespace),
+                Comment => leaf!(Comment),
+                Pipe => chain!(leaf!(Pipe), call!(PipelineCont)),
+                PlainText | DoubleQuote | OpeningParenthesis | EscapedChar => call!(Command),
+                Newlines | Semicolon | ClosingParenthesis | Eof => ret!(),
+            },
+            NodeKind::PipelineCont => match self.lookahead.kind {
+                Whitespace => leaf!(Whitespace),
+                Newlines => leaf!(Newlines),
+                Comment => leaf!(Comment),
+                PlainText | DoubleQuote | OpeningParenthesis | EscapedChar => {
+                    chain!(call!(Command), ret!())
+                }
+                Semicolon => chain_buf!(chain!(error!(UnexpectedSemicolon), ret!()), ret!()),
+                Pipe => chain!(error!(UnexpectedPipe), ret!()),
+                ClosingParenthesis => chain!(error!(UnexpectedClosingParenthesis), ret!()),
+                Eof => chain!(error!(UnexpectedEof), ret!()),
+            },
+            NodeKind::Command => match self.lookahead.kind {
+                Whitespace => leaf!(Whitespace),
+                Comment => leaf!(Comment),
+                PlainText | DoubleQuote | OpeningParenthesis | EscapedChar => call!(Word),
+                Newlines | Semicolon | Pipe | ClosingParenthesis | Eof => ret!(),
+            },
+            NodeKind::Word => match self.lookahead.kind {
+                PlainText => leaf!(PlainText),
+                EscapedChar => leaf!(EscapedChar),
+                DoubleQuote => chain_buf!(call!(DQuotedString), leaf!(DoubleQuote, String)),
+                OpeningParenthesis => {
+                    chain_buf!(call!(CommandSubstitution), leaf!(OpeningParenthesis))
+                }
+                Comment | Whitespace | Newlines | Semicolon | Pipe | ClosingParenthesis | Eof => {
+                    ret!()
+                }
+            },
+            NodeKind::DQuotedString => match self.lookahead.kind {
+                PlainText => leaf!(PlainText, String),
+                EscapedChar => leaf!(EscapedChar, String),
+                DoubleQuote => chain_buf!(leaf!(DoubleQuote, Command), ret!()),
+                OpeningParenthesis => chain_buf!(
+                    call!(CommandSubstitution),
+                    leaf!(OpeningParenthesis, Command)
+                ),
+                ClosingParenthesis => error!(UnexpectedClosingParenthesis, String),
+                Eof => chain_buf!(error!(UnexpectedEof, Command), ret!()),
                 _ => unreachable!(),
             },
+            _ => unreachable!(),
         }
     }
 }