evaluate each block key in child scope - fixes #1397

src/compile/nodes/EachBlock.ts

@@ -31,10 +31,6 @@ export default class EachBlock extends Node {
 		this.context = info.context.name || 'each'; // TODO this is used to facilitate binding; currently fails with destructuring
 		this.index = info.index;
 
-		this.key = info.key
-			? new Expression(compiler, this, scope, info.key)
-			: null;
-
 		this.scope = scope.child();
 
 		this.contexts = [];
@@ -50,6 +46,10 @@ export default class EachBlock extends Node {
 			this.scope.add(this.index, dependencies);
 		}
 
+		this.key = info.key
+			? new Expression(compiler, this, this.scope, info.key)
+			: null;
+
 		this.children = mapChildren(compiler, this, this.scope, info.children);
 
 		this.else = info.else

test/runtime/samples/dev-warning-missing-data-each/_config.js

@@ -0,0 +1,22 @@
+export default {
+	dev: true,
+
+	data: {
+		letters: [
+			{
+				id: 1,
+				char: 'a',
+			},
+			{
+				id: 2,
+				char: 'b',
+			},
+			{
+				id: 3,
+				char: 'c',
+			},
+		],
+	},
+
+	warnings: [],
+};

test/runtime/samples/dev-warning-missing-data-each/main.html

@@ -0,0 +1,3 @@
+{#each letters as letter (letter.id)}
+  <div>{letter.char}</div>
+{/each}