[pull] master from microsoft:master

pxtblocks/monkeyPatches/connection.ts

@@ -0,0 +1,20 @@
+import * as Blockly from "blockly";
+
+export function monkeyPatchConnection() {
+    const oldConnectionForOrphanedConnection = Blockly.Connection.getConnectionForOrphanedConnection;
+    Blockly.Connection.getConnectionForOrphanedConnection = function (startBlock: Blockly.Block, orphanConnection: Blockly.Connection) {
+        // When a block is dragged into an input that already has a non-shadow block connected, Blockly has
+        // some logic that checks to see if the block you just dragged has a single input and, if so, connects
+        // the previously connected block to the input of the block you just dragged. Presumably this is to make
+        // it easier to wrap blocks with a new block (for example, dragging an absolute value block onto a number
+        // in an equation will wrap it theoretically saving you an extra drag). However, nobody ever expects this
+        // behavior and only the most powerful of power users would use it to their advantage. It also can cause
+        // type errors when the displaced block is a variable since variables can be connected to any input regardless
+        // of what type they actually hold. It's better to just disable it entirely.
+        if (orphanConnection.type === Blockly.ConnectionType.OUTPUT_VALUE) {
+            return null;
+        }
+
+        return oldConnectionForOrphanedConnection(startBlock, orphanConnection);
+    }
+}

pxtblocks/monkeyPatches/index.ts

@@ -1,4 +1,5 @@
 import { monkeyPatchBlockSvg } from "./blockSvg";
+import { monkeyPatchConnection } from "./connection";
 import { monkeyPatchGesture } from "./gesture";
 import { monkeyPatchGrid } from "./grid";
 import { monkeyPatchAddKeyMapping } from "./shortcut_registry";
@@ -8,4 +9,5 @@ export function applyMonkeyPatches() {
     monkeyPatchGrid();
     monkeyPatchGesture();
     monkeyPatchAddKeyMapping();
+    monkeyPatchConnection();
 }