Isolated for untyped anonymous functions

Part of #145.

lang/spec.html

@@ -5041,7 +5041,8 @@ <h3>Anonymous function expression</h3>
 </pre>
 <p>
 An infer-anonymous-function-expr can only be used in a context where a function
-type is expected. The types of the parameters are inferred from the expected
+type is expected. Both the types of the parameters and whether the function is
+isolated are inferred from the expected
 function type. The scope of the parameters is <code>expr-function-body</code>.
 The static type of the infer-anonymous-function-expr will be a function type
 whose return type is the static type of the <code>expression</code> in