feat(compiler-core/v-model): error when v-model is used on scope variable

packages/compiler-core/src/errors.ts

@@ -81,6 +81,7 @@ export const enum ErrorCodes {
   X_V_SLOT_MISPLACED,
   X_V_MODEL_NO_EXPRESSION,
   X_V_MODEL_MALFORMED_EXPRESSION,
+  X_V_MODEL_ON_SCOPE_VARIABLE,
 
   // generic errors
   X_PREFIX_ID_NOT_SUPPORTED,
@@ -171,6 +172,7 @@ export const errorMessages: { [code: number]: string } = {
   [ErrorCodes.X_V_SLOT_MISPLACED]: `v-slot can only be used on components or <template> tags.`,
   [ErrorCodes.X_V_MODEL_NO_EXPRESSION]: `v-model is missing expression.`,
   [ErrorCodes.X_V_MODEL_MALFORMED_EXPRESSION]: `v-model value must be a valid JavaScript member expression.`,
+  [ErrorCodes.X_V_MODEL_ON_SCOPE_VARIABLE]: `v-model cannot be used on v-for or v-slot scope variables because they are not writable.`,
 
   // generic errors
   [ErrorCodes.X_PREFIX_ID_NOT_SUPPORTED]: `"prefixIdentifiers" option is not supported in this build of compiler.`,

packages/compiler-core/src/transforms/vModel.ts

@@ -9,7 +9,7 @@ import {
   createInterpolation
 } from '../ast'
 import { createCompilerError, ErrorCodes } from '../errors'
-import { isMemberExpression } from '../utils'
+import { isMemberExpression, isSimpleIdentifier } from '../utils'
 import { isObject } from '@vue/shared'
 
 export const transformModel: DirectiveTransform = (dir, node, context) => {
@@ -30,6 +30,18 @@ export const transformModel: DirectiveTransform = (dir, node, context) => {
     return createTransformProps()
   }
 
+  if (
+    !__BROWSER__ &&
+    context.prefixIdentifiers &&
+    isSimpleIdentifier(expString) &&
+    context.identifiers[expString]
+  ) {
+    context.onError(
+      createCompilerError(ErrorCodes.X_V_MODEL_ON_SCOPE_VARIABLE, exp.loc)
+    )
+    return createTransformProps()
+  }
+
   const propName = arg ? arg : createSimpleExpression('modelValue', true)
   const eventName = arg
     ? arg.type === NodeTypes.SIMPLE_EXPRESSION && arg.isStatic