yield now behaves as expected around 'this' - fixes https://github.com/jashkenas/coffeescript/issues/3882

lib/coffee-script/nodes.js

@@ -87,7 +87,7 @@
     };
 
     Base.prototype.compileClosure = function(o) {
-      var args, argumentsNode, func, jumpNode, meth, parts;
+      var args, argumentsNode, func, jumpNode, meth, parts, ref3;
       if (jumpNode = this.jumps()) {
         jumpNode.error('cannot use a pure statement in an expression');
       }
@@ -105,7 +105,7 @@
         func = new Value(func, [new Access(new Literal(meth))]);
       }
       parts = (new Call(func, args)).compileNode(o);
-      if (func.isGenerator) {
+      if (func.isGenerator || ((ref3 = func.base) != null ? ref3.isGenerator : void 0)) {
         parts.unshift(this.makeCode("(yield* "));
         parts.push(this.makeCode(")"));
       }

src/nodes.coffee

@@ -90,7 +90,7 @@ exports.Base = class Base
         meth = 'call'
       func = new Value func, [new Access new Literal meth]
     parts = (new Call func, args).compileNode o
-    if func.isGenerator
+    if func.isGenerator or func.base?.isGenerator
       parts.unshift @makeCode "(yield* "
       parts.push    @makeCode ")"
     parts

test/generators.coffee

@@ -218,3 +218,50 @@ test "symbolic operators has precedence over the `yield`", ->
     mapped  = CoffeeScript.eval "(arr) ->       (#{expression} for i in arr)"
 
     arrayEq mapped(values), collect yielded values
+
+test "yield handles 'this' correctly", ->
+  x = ->
+    yield switch
+      when true then yield => this
+    yield for item in [1]
+      yield => this
+    yield if true then yield => this
+    yield try throw yield => this
+    throw yield => this
+
+  y = x.call [1, 2, 3]
+
+  z = y.next()
+  arrayEq z.value(), [1, 2, 3]
+  ok z.done is false
+
+  z = y.next 123
+  ok z.value is 123 and z.done is false
+
+  z = y.next()
+  arrayEq z.value(), [1, 2, 3]
+  ok z.done is false
+
+  z = y.next 42
+  arrayEq z.value, [42]
+  ok z.done is false
+
+  z = y.next()
+  arrayEq z.value(), [1, 2, 3]
+  ok z.done is false
+
+  z = y.next 456
+  ok z.value is 456 and z.done is false
+
+  z = y.next()
+  arrayEq z.value(), [1, 2, 3]
+  ok z.done is false
+
+  z = y.next new Error "ignore me"
+  ok z.value is undefined and z.done is false
+
+  z = y.next()
+  arrayEq z.value(), [1, 2, 3]
+  ok z.done is false
+
+  throws -> y.next new Error "boom"