Infer types inside yield expressions

This sets the inferred type of the YIELD expression itself to the unknown type, since calling .next(expression) on the generator will change its value. ------------- Created by MOE: https://github.com/google/moe MOE_MIGRATED_REVID=188408405
google · Mar 9, 2018 · 9202dc1 · 9202dc1
1 parent 50b689f
commit 9202dc1
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Showing 2 changed files with 34 additions and 4 deletions.
diff --git a/src/com/google/javascript/jscomp/TypeInference.java b/src/com/google/javascript/jscomp/TypeInference.java
@@ -451,6 +451,11 @@ private FlowScope traverse(Node n, FlowScope scope) {
         scope = traverseReturn(n, scope);
         break;
 
+      case YIELD:
+        scope = traverseChildren(n, scope);
+        n.setJSType(getNativeType(UNKNOWN_TYPE));
+        break;
+
       case VAR:
       case THROW:
         scope = traverseChildren(n, scope);

diff --git a/test/com/google/javascript/jscomp/TypeInferenceTest.java b/test/com/google/javascript/jscomp/TypeInferenceTest.java
@@ -16,6 +16,7 @@
 
 package com.google.javascript.jscomp;
 
+import static com.google.javascript.jscomp.CompilerTypeTestCase.lines;
 import static com.google.javascript.rhino.jstype.JSTypeNative.ALL_TYPE;
 import static com.google.javascript.rhino.jstype.JSTypeNative.ARRAY_TYPE;
 import static com.google.javascript.rhino.jstype.JSTypeNative.BOOLEAN_TYPE;
@@ -34,7 +35,6 @@
 import com.google.common.base.Joiner;
 import com.google.common.collect.ImmutableList;
 import com.google.javascript.jscomp.CodingConvention.AssertionFunctionSpec;
-import com.google.javascript.jscomp.CompilerOptions.LanguageMode;
 import com.google.javascript.jscomp.DataFlowAnalysis.BranchedFlowState;
 import com.google.javascript.jscomp.type.FlowScope;
 import com.google.javascript.jscomp.type.ReverseAbstractInterpreter;
@@ -75,7 +75,6 @@ public void setUp() {
     compiler = new Compiler();
     CompilerOptions options = new CompilerOptions();
     options.setClosurePass(true);
-    options.setLanguageIn(LanguageMode.ECMASCRIPT5);
     compiler.initOptions(options);
     registry = compiler.getTypeRegistry();
     assumptions = new HashMap<>();
@@ -99,8 +98,15 @@ private void inFunction(String js) {
     String thisBlock = assumedThisType == null
         ? ""
         : "/** @this {" + assumedThisType + "} */";
-    Node root = compiler.parseTestCode(
-        "(" + thisBlock + " function() {" + js + "});");
+    parseAndRunTypeInference("(" + thisBlock + " function() {" + js + "});");
+  }
+
+  private void inGenerator(String js) {
+    parseAndRunTypeInference("(function *() {" + js + "});");
+  }
+
+  private void parseAndRunTypeInference(String js) {
+    Node root = compiler.parseTestCode(js);
     assertEquals("parsing error: " +
         Joiner.on(", ").join(compiler.getErrors()),
         0, compiler.getErrorCount());
@@ -1531,6 +1537,25 @@ public void testNotIsArray() {
     verify("x", NUMBER_TYPE);
   }
 
+  public void testYield1() {
+    inGenerator("var x = yield 3;");
+    verify("x", registry.getNativeType(UNKNOWN_TYPE));
+  }
+
+  public void testYield2() {
+    // test that type inference happens inside the yield expression
+    inGenerator(
+        lines(
+            "var obj;",
+            "yield (obj = {a: 3, b: '4'});",
+            "var a = obj.a;",
+            "var b = obj.b;"
+        ));
+
+    verify("a", registry.getNativeType(NUMBER_TYPE));
+    verify("b", registry.getNativeType(STRING_TYPE));
+  }
+
   private ObjectType getNativeObjectType(JSTypeNative t) {
     return registry.getNativeObjectType(t);
   }