parser: Disable Hack pipes + v8intrinsic/placeholders

We may reenable combining these again if TC39 ends up deciding to use % as a topic token.
See babel#13416 (comment).

packages/babel-parser/src/plugin-utils.js

@@ -90,6 +90,18 @@ export function validatePlugins(plugins: PluginList) {
       getPluginOption(plugins, "recordAndTuple", "syntaxType") === "hash";
 
     if (proposal === "hack") {
+      if (hasPlugin(plugins, "placeholders")) {
+        throw new Error(
+          "Cannot combine placeholders plugin and Hack-style pipes.",
+        );
+      }
+
+      if (hasPlugin(plugins, "v8intrinsic")) {
+        throw new Error(
+          "Cannot combine v8intrinsic plugin and Hack-style pipes.",
+        );
+      }
+
       const topicToken = getPluginOption(
         plugins,
         "pipelineOperator",

packages/babel-parser/src/plugins/v8intrinsic.js

@@ -6,7 +6,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
   class extends superClass {
     parseV8Intrinsic(): N.Expression {
       if (this.match(tt.modulo)) {
-        const start = this.state.start;
+        const v8IntrinsicStart = this.state.start;
         // let the `loc` of Identifier starts from `%`
         const node = this.startNode();
         this.eat(tt.modulo);
@@ -18,32 +18,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
             return identifier;
           }
         }
-
-        // In this case, the `%` currently being parsed is not followed by an identifier,
-        // so it therefore cannot be a V8 intrinsic.
-        // If the `pipelineOperator` plugin is active,
-        // then the `%` currently being parsed may instead be a topic reference.
-        const pipeProposal = this.getPluginOption(
-          "pipelineOperator",
-          "proposal",
-        );
-        if (pipeProposal) {
-          // A pipe-operator proposal is active,
-          // although its configuration might not match `%` as a topic token.
-          // If the pipe-operator plugin’s configuration matches the current token’s type,
-          // then this will return `node`, will have been finished as a topic reference.
-          // Otherwise, this will throw a `PipeTopicUnconfiguredToken` error.
-          return this.finishTopicReference(
-            node,
-            start,
-            pipeProposal,
-            tt.modulo,
-          );
-        } else {
-          // A pipe-operator proposal is not active.
-          // Throw a fatal syntax error.
-          this.unexpected(start);
-        }
+        this.unexpected(v8IntrinsicStart);
       }
     }