Early name check

src/main/scala/millfork/compiler/MfCompiler.scala

@@ -45,6 +45,7 @@ object MlCompiler {
   def nextLabel(prefix: String): String = "." + prefix + "__" + labelCounter.incrementAndGet().formatted("%05d")
 
   def compile(ctx: CompilationContext): Chunk = {
+    ctx.env.nameCheck(ctx.function.code)
     val chunk = compile(ctx, ctx.function.code)
     val prefix = (if (ctx.function.interrupt) {
       if (ctx.options.flag(CompilationFlag.EmitCmosOpcodes)) {

src/main/scala/millfork/env/Environment.scala

@@ -3,7 +3,7 @@ package millfork.env
 import java.util.concurrent.atomic.AtomicLong
 
 import millfork.{CompilationFlag, CompilationOptions}
-import millfork.assembly.Opcode
+import millfork.assembly.{Opcode, OpcodeClasses}
 import millfork.compiler._
 import millfork.error.ErrorReporting
 import millfork.node._
@@ -692,4 +692,33 @@ class Environment(val parent: Option[Environment], val prefix: String) {
       case i: ImportStatement => ()
     }
   }
+
+  private def checkName[T <: Thing : Manifest](name: String, pos: Option[Position]): Unit = {
+    if (maybeGet[T](name).isEmpty) {
+      ErrorReporting.error(s"`$name` is not defined", pos)
+    }
+  }
+
+  def nameCheck(nodes: List[_ <:Node]): Unit = nodes.foreach(nameCheck)
+
+  def nameCheck(node: Node): Unit = node match {
+    case _:AssemblyStatement => ()
+    case _:DeclarationStatement => ()
+    case s:Statement => nameCheck(s.getAllExpressions)
+    case _:LiteralExpression => ()
+    case VariableExpression(name) => checkName[Thing](name, node.position)
+    case IndexedExpression(name, index) =>
+      checkName[Thing](name, node.position)
+      nameCheck(index)
+    case SeparateBytesExpression(h, l) =>
+      nameCheck(h)
+      nameCheck(l)
+    case SumExpression(params, _) =>
+      nameCheck(params.map(_._2))
+    case FunctionCallExpression(name, params) =>
+      if (name.exists(_.isLetter) && name != "not") {
+        checkName[MangledFunction](name, node.position)
+      }
+      nameCheck(params)
+  }
 }

src/test/scala/millfork/test/AssemblyOptimizationSuite.scala

@@ -259,7 +259,7 @@ class AssemblyOptimizationSuite extends FunSuite with Matchers {
         |   }
         |   a.lo:a.hi=a
         |   output = a
-        |   couput
+        |   output
         | }
         | void barrier (){}
         |