diff --git a/examples/numbers.pork b/examples/numbers.pork
index 19f0834..1ed2e9a 100644
--- a/examples/numbers.pork
+++ b/examples/numbers.pork
@@ -1,4 +1,5 @@
 export func main() {
   let pi = 3.141592653589793
   println(pi)
+
 }
diff --git a/parser/src/main/kotlin/gay/pizza/pork/parser/ParseError.kt b/parser/src/main/kotlin/gay/pizza/pork/parser/ParseError.kt
index 43ad464..e6004a2 100644
--- a/parser/src/main/kotlin/gay/pizza/pork/parser/ParseError.kt
+++ b/parser/src/main/kotlin/gay/pizza/pork/parser/ParseError.kt
@@ -1,3 +1,3 @@
 package gay.pizza.pork.parser
 
-class ParseError(val error: String) : RuntimeException(error)
+open class ParseError(val error: String) : RuntimeException(error)
diff --git a/parser/src/main/kotlin/gay/pizza/pork/parser/Parser.kt b/parser/src/main/kotlin/gay/pizza/pork/parser/Parser.kt
index 3532d73..56114c5 100644
--- a/parser/src/main/kotlin/gay/pizza/pork/parser/Parser.kt
+++ b/parser/src/main/kotlin/gay/pizza/pork/parser/Parser.kt
@@ -16,7 +16,7 @@ class Parser(source: TokenSource, attribution: NodeAttribution) :
     Block(items)
   }
 
-  override fun parseExpression(): Expression {
+  override fun parseExpression(): Expression = guarded {
     val token = peek()
     val expression = when (token.type) {
       TokenType.NumberLiteral -> parseNumberLiteral()
@@ -37,7 +37,7 @@ class Parser(source: TokenSource, attribution: NodeAttribution) :
       TokenType.None -> parseNoneLiteral()
 
       else -> {
-        throw gay.pizza.pork.parser.ParseError(
+        throw ParseError(
           "Failed to parse token: ${token.type} '${token.text}' as" +
             " expression (index ${source.currentIndex})"
         )
@@ -45,7 +45,7 @@ class Parser(source: TokenSource, attribution: NodeAttribution) :
     }
 
     if (expression is SymbolReference && peek(TokenType.Equals)) {
-      return guarded {
+      return@guarded guarded {
         attribution.adopt(expression)
         expect(TokenType.Equals)
         val value = parseExpression()
@@ -53,7 +53,7 @@ class Parser(source: TokenSource, attribution: NodeAttribution) :
       }
     }
 
-    return if (peek(
+    return@guarded if (peek(
         TokenType.Plus,
         TokenType.Minus,
         TokenType.Multiply,
@@ -138,7 +138,7 @@ class Parser(source: TokenSource, attribution: NodeAttribution) :
     return modifiers
   }
 
-  fun maybeParseDefinition(): Definition? {
+  private fun maybeParseDefinition(): Definition? {
     try {
       storedDefinitionModifiers = parseDefinitionModifiers()
       val token = peek()
@@ -152,19 +152,19 @@ class Parser(source: TokenSource, attribution: NodeAttribution) :
     }
   }
 
-  override fun parseDeclaration(): Declaration {
+  override fun parseDeclaration(): Declaration = guarded {
     val token = peek()
-    return when (token.type) {
+    return@guarded when (token.type) {
       TokenType.Import -> parseImportDeclaration()
-      else -> throw gay.pizza.pork.parser.ParseError(
+      else -> throw ParseError(
         "Failed to parse token: ${token.type} '${token.text}' as" +
           " declaration (index ${source.currentIndex})"
       )
     }
   }
 
-  override fun parseDefinition(): Definition {
-    return maybeParseDefinition() ?: throw ParseError("Unable to parse definition")
+  override fun parseDefinition(): Definition = guarded {
+    maybeParseDefinition() ?: throw ParseError("Unable to parse definition")
   }
 
   override fun parseDoubleLiteral(): DoubleLiteral = guarded {
diff --git a/parser/src/main/kotlin/gay/pizza/pork/parser/ParserBase.kt b/parser/src/main/kotlin/gay/pizza/pork/parser/ParserBase.kt
index ee7cdee..d5b959f 100644
--- a/parser/src/main/kotlin/gay/pizza/pork/parser/ParserBase.kt
+++ b/parser/src/main/kotlin/gay/pizza/pork/parser/ParserBase.kt
@@ -4,8 +4,6 @@ import gay.pizza.pork.ast.Node
 import gay.pizza.pork.ast.NodeParser
 
 abstract class ParserBase(val source: TokenSource, val attribution: NodeAttribution) : NodeParser {
-  open class ParseError(error: String) : RuntimeException(error)
-
   class ExpectedTokenError(got: Token, vararg expectedTypes: TokenType) : ParseError(
     "Expected one of ${expectedTypes.joinToString(", ")}" +
       " but got type ${got.type} '${got.text}'"
diff --git a/parser/src/main/kotlin/gay/pizza/pork/parser/ParserHelpers.kt b/parser/src/main/kotlin/gay/pizza/pork/parser/ParserHelpers.kt
index c7c7377..e308741 100644
--- a/parser/src/main/kotlin/gay/pizza/pork/parser/ParserHelpers.kt
+++ b/parser/src/main/kotlin/gay/pizza/pork/parser/ParserHelpers.kt
@@ -23,7 +23,7 @@ internal object ParserHelpers {
     TokenType.GreaterEqual -> InfixOperator.GreaterEqual
     TokenType.And -> InfixOperator.BooleanAnd
     TokenType.Or -> InfixOperator.BooleanOr
-    else -> throw ParserBase.ParseError("Unknown Infix Operator")
+    else -> throw ParseError("Unknown Infix Operator")
   }
 
   fun convertPrefixOperator(token: Token): PrefixOperator = when (token.type) {
@@ -31,12 +31,12 @@ internal object ParserHelpers {
     TokenType.Plus -> PrefixOperator.UnaryPlus
     TokenType.Minus -> PrefixOperator.UnaryMinus
     TokenType.Tilde -> PrefixOperator.BinaryNot
-    else -> throw ParserBase.ParseError("Unknown Prefix Operator")
+    else -> throw ParseError("Unknown Prefix Operator")
   }
 
   fun convertSuffixOperator(token: Token): SuffixOperator = when (token.type) {
     TokenType.PlusPlus -> SuffixOperator.Increment
     TokenType.MinusMinus -> SuffixOperator.Decrement
-    else -> throw ParserBase.ParseError("Unknown Suffix Operator")
+    else -> throw ParseError("Unknown Suffix Operator")
   }
 }
diff --git a/support/pork-idea/src/main/kotlin/gay/pizza/pork/idea/PsiBuilderMarkAttribution.kt b/support/pork-idea/src/main/kotlin/gay/pizza/pork/idea/PsiBuilderMarkAttribution.kt
index fc7a836..733f63b 100644
--- a/support/pork-idea/src/main/kotlin/gay/pizza/pork/idea/PsiBuilderMarkAttribution.kt
+++ b/support/pork-idea/src/main/kotlin/gay/pizza/pork/idea/PsiBuilderMarkAttribution.kt
@@ -4,14 +4,17 @@ import com.intellij.lang.PsiBuilder
 import gay.pizza.pork.ast.Node
 import gay.pizza.pork.parser.ParseError
 import gay.pizza.pork.parser.ParserNodeAttribution
+import java.util.IdentityHashMap
 
 class PsiBuilderMarkAttribution(val builder: PsiBuilder) : ParserNodeAttribution() {
+  private val map = IdentityHashMap<Node, Node>()
+
   override fun <T : Node> guarded(block: () -> T): T {
     val marker = builder.mark()
-    try {
+    val result = try {
       val item = super.guarded(block)
       marker.done(PorkElementTypes.elementTypeFor(item.type))
-      return item
+      item
     } catch (e: PsiBuilderTokenSource.BadCharacterError) {
       marker.error("Bad character.")
       while (!builder.eof()) {
@@ -32,5 +35,10 @@ class PsiBuilderMarkAttribution(val builder: PsiBuilder) : ParserNodeAttribution
       }
       throw PorkParser.ExitParser()
     }
+    if (map[result] != null) {
+      marker.drop()
+    }
+    map[result] = result
+    return result
   }
 }