Don't warn for "missing return statement" in a generator function

This fixes some errors seen when moving generator transpilation after CheckMissingReturn. ------------- Created by MOE: https://github.com/google/moe MOE_MIGRATED_REVID=191603599
google · Apr 4, 2018 · 38c5d06 · 38c5d06
1 parent 68e2fd4
commit 38c5d06
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diff --git a/src/com/google/javascript/jscomp/CheckMissingReturn.java b/src/com/google/javascript/jscomp/CheckMissingReturn.java
@@ -98,6 +98,12 @@ public void enterScope(NodeTraversal t) {
       return;
     }
 
+    if (n.isGeneratorFunction()) {
+      // Generator functions always return a Generator. No need to check return statements.
+      // TODO(b/73387406): Investigate adding a warning for generators with no yields.
+      return;
+    }
+
     if (n.isArrowFunction()) {
       Node functionBody = NodeUtil.getFunctionBody(n);
       if (!functionBody.isNormalBlock()) {

diff --git a/test/com/google/javascript/jscomp/CheckMissingReturnTest.java b/test/com/google/javascript/jscomp/CheckMissingReturnTest.java
@@ -300,4 +300,26 @@ public void testArrowFunctions() {
     // arrow function return is object literal
     testSame("(a) => ({foo: 1});");
   }
+
+  public void testGeneratorFunctionDoesntWarn() {
+    setAcceptedLanguage(LanguageMode.ECMASCRIPT_2015);
+    testNoWarning("function *gen() {}");
+
+    testNoWarning(
+        lines(
+            "/** @return {!Generator<number>} */", // no yields is OK
+            "function *gen() {}"));
+
+    testNoWarning(
+        lines(
+            "/** @return {!Generator<number>} */", // one yield is OK
+            "function *gen() {",
+            " yield 1;",
+            "}"));
+
+    testNoWarning(
+        lines(
+            "/** @return {!Object} */", // Return type more vague than Generator is also OK
+            "function *gen() {}"));
+  }
 }