refactor(compiler-sfc): always parse explicit script setup signature

packages/compiler-sfc/src/compileScript.ts

@@ -366,10 +366,8 @@ export function compileScript(
   // record declared types for runtime props type generation
   const declaredTypes: Record<string, string[]> = {}
 
-  if (isTS && hasExplicitSignature) {
-    // <script setup="xxx" lang="ts">
-    // parse the signature to extract the props/emit variables the user wants
-    // we need them to find corresponding type declarations.
+  // <script setup="xxx">
+  if (hasExplicitSignature) {
     let signatureAST
     try {
       signatureAST = _parse(`(${setupValue})=>{}`, { plugins }).program.body[0]
@@ -382,6 +380,11 @@ export function compileScript(
         )}`
       )
     }
+
+    if (isTS) {
+      // <script setup="xxx" lang="ts">
+      // parse the signature to extract the props/emit variables the user wants
+      // we need them to find corresponding type declarations.
       const params = ((signatureAST as ExpressionStatement)
         .expression as ArrowFunctionExpression).params
       if (params[0] && params[0].type === 'Identifier') {
@@ -407,6 +410,7 @@ export function compileScript(
         }
       }
     }
+  }
 
   // 3. parse <script setup> and  walk over top level statements
   const scriptSetupAst = parse(