Warns when mutated props are passed.

src/renderers/shared/reconciler/ReactCompositeComponent.js

@@ -27,6 +27,7 @@ var emptyObject = require('emptyObject');
 var invariant = require('invariant');
 var shouldUpdateReactComponent = require('shouldUpdateReactComponent');
 var warning = require('warning');
+var shallowEqual = require('shallowEqual');
 
 function getDeclarationErrorAddendum(component) {
   var owner = component._currentElement._owner || null;
@@ -147,6 +148,7 @@ var ReactCompositeComponentMixin = {
     // Initialize the public class
     var inst;
     var renderedElement;
+    var propsMutated;
 
     // This is a way to detect if Component is a stateless arrow function
     // component, which is not newable. It might not be 100% reliable but is
@@ -195,6 +197,15 @@ var ReactCompositeComponentMixin = {
           Component.displayName || Component.name || 'Component'
         );
       }
+
+      propsMutated = !shallowEqual(inst.props, publicProps);
+      if (propsMutated) {
+        warning(
+          propsMutated,
+          'Mutated props not allowed in %s(...)',
+          Component.displayName || Component.name || 'Component'
+        );
+      }
     }
 
     // These should be set up in the constructor, but as a convenience for