fix repl error recovery

bin/repl

@@ -144,19 +144,33 @@ async function repl() {
       return
     }
 
-    codeHistory.push(trimmed)
-
     try {
       const compiler = new Compiler(trimmed, Object.keys(globals))
 
-      vm.appendBytecode(compiler.bytecode)
+      // Save VM state before appending bytecode, in case execution fails
+      const savedInstructions = [...vm.instructions]
+      const savedConstants = [...vm.constants]
+      const savedPc = vm.pc
+      const savedScope = vm.scope
+      const savedStopped = vm.stopped
 
-      const result = await vm.continue()
+      try {
+        vm.appendBytecode(compiler.bytecode)
+        const result = await vm.continue()
 
-      console.log(`${colors.dim}=>${colors.reset} ${formatValue(result)}`)
+        codeHistory.push(trimmed)
+        console.log(`${colors.dim}=>${colors.reset} ${formatValue(result)}`)
+      } catch (error: any) {
+        vm.instructions = savedInstructions
+        vm.constants = savedConstants
+        vm.pc = savedPc
+        vm.scope = savedScope
+        vm.stopped = savedStopped
+
+        console.log(`\n${colors.red}Error:${colors.reset} ${error.message}`)
+      }
     } catch (error: any) {
       console.log(`\n${colors.red}Error:${colors.reset} ${error.message}`)
-      codeHistory.pop()
     }
 
     rl.prompt()