fix(parser): throw error with wrong typescript 'export declare' (#12684)

packages/babel-parser/src/plugins/typescript/index.js

@@ -74,6 +74,8 @@ const TSErrors = Object.freeze({
   EmptyHeritageClauseType: "'%0' list cannot be empty.",
   EmptyTypeArguments: "Type argument list cannot be empty.",
   EmptyTypeParameters: "Type parameter list cannot be empty.",
+  ExpectedAmbientAfterExportDeclare:
+    "'export declare' must be followed by an ambient declaration.",
   IndexSignatureHasAbstract:
     "Index signatures cannot have the 'abstract' modifier",
   IndexSignatureHasAccessibility:
@@ -2281,6 +2283,16 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       // "export declare" is equivalent to just "export".
       const isDeclare = this.eatContextual("declare");
 
+      if (
+        isDeclare &&
+        (this.isContextual("declare") || !this.shouldParseExportDeclaration())
+      ) {
+        throw this.raise(
+          this.state.start,
+          TSErrors.ExpectedAmbientAfterExportDeclare,
+        );
+      }
+
       let declaration: ?N.Declaration;
 
       if (this.match(tt.name)) {