src: turn buffer type-CHECK into exception

Turn a `CHECK()` that could be brought to fail using public APIs
into throwing an error.

Fixes: nodejs#12152

src/stream_base.cc

@@ -189,9 +189,14 @@ int StreamBase::Writev(const FunctionCallbackInfo<Value>& args) {
 
 int StreamBase::WriteBuffer(const FunctionCallbackInfo<Value>& args) {
   CHECK(args[0]->IsObject());
-  CHECK(Buffer::HasInstance(args[1]));
+
   Environment* env = Environment::GetCurrent(args);
 
+  if (!args[1]->IsUint8Array()) {
+    env->ThrowTypeError("Second argument must be a buffer");
+    return 0;
+  }
+
   Local<Object> req_wrap_obj = args[0].As<Object>();
   const char* data = Buffer::Data(args[1]);
   size_t length = Buffer::Length(args[1]);

test/parallel/test-stream-base-typechecking.js

@@ -0,0 +1,7 @@
+'use strict';
+require('../common');
+const assert = require('assert');
+
+assert.throws(() => {
+  process.stdout.write('broken', 'buffer');
+}, /^TypeError: Second argument must be a buffer$/);