buffer: improve .from() error details

This makes sure the original input is passed to the error in case
no matching inputs are found. Instead of passing along all values,
only valid or possibliy valid values are passed through. That way
invalid values end up in the error case with the original input.

PR-URL: #29675
Reviewed-By: Rich Trott <rtrott@gmail.com>

lib/buffer.js

@@ -292,17 +292,21 @@ Buffer.from = function from(value, encodingOrOffset, length) {
       return fromArrayBuffer(value, encodingOrOffset, length);
 
     const valueOf = value.valueOf && value.valueOf();
-    if (valueOf !== null && valueOf !== undefined && valueOf !== value)
-      return Buffer.from(valueOf, encodingOrOffset, length);
+    if (valueOf != null &&
+        valueOf !== value &&
+        (typeof valueOf === 'string' || typeof valueOf === 'object')) {
+      return from(valueOf, encodingOrOffset, length);
+    }
 
     const b = fromObject(value);
     if (b)
       return b;
 
     if (typeof value[SymbolToPrimitive] === 'function') {
-      return Buffer.from(value[SymbolToPrimitive]('string'),
-                         encodingOrOffset,
-                         length);
+      const primitive = value[SymbolToPrimitive]('string');
+      if (typeof primitive === 'string') {
+        return fromString(primitive, encodingOrOffset);
+      }
     }
   }