[NTI] Type the global THIS more precisely than ?.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=130691769

src/com/google/javascript/jscomp/GlobalTypeInfo.java

@@ -418,6 +418,7 @@ public void process(Node externs, Node root) {
       }
       checkAndFinalizeNominalType(rawType);
     }
+    JSType globalThisType;
     if (win != null) {
       // Copy properties from window to Window.prototype, because in rare cases
       // people pass window around rather than using it directly.
@@ -426,7 +427,15 @@ public void process(Node externs, Node root) {
         winNs.copyWindowProperties(this.commonTypes, win);
       }
       checkAndFinalizeNominalType(win);
+      // Type the global THIS as window
+      globalThisType = win.getInstanceAsJSType();
+    } else {
+      // Type the global THIS as a loose object
+      globalThisType = JSType.TOP_OBJECT.withLoose();
     }
+    this.globalScope.setDeclaredType(
+        (new FunctionTypeBuilder(this.commonTypes)).
+        addReceiverType(globalThisType).buildDeclaration());
 
     nominaltypesByNode = null;
     propertyDefs = null;

src/com/google/javascript/jscomp/NTIScope.java

@@ -78,8 +78,8 @@ final class NTIScope implements DeclaredTypeRegistry {
   // The set localEnums is used for enum resolution, and then discarded.
   private Set<EnumType> localEnums = new LinkedHashSet<>();
 
-  // declaredType is null for top level, but never null for functions,
-  // even those without jsdoc.
+  // For top level, the DeclaredFunctionType just includes a type for THIS.
+  // For functions, the DeclaredFunctionType is never null, even those without jsdoc.
   // Any inferred parameters or return will be set to null individually.
   private DeclaredFunctionType declaredType;
 
@@ -321,11 +321,8 @@ boolean isEscapedVar(String name) {
   }
 
   boolean hasThis() {
-    if (!isFunction()) {
-      return false;
-    }
-    DeclaredFunctionType dft = getDeclaredFunctionType();
-    // dft is null for function scopes early during GlobalTypeInfo
+    DeclaredFunctionType dft = this.declaredType;
+    // dft is null early during GlobalTypeInfo
     return dft != null && dft.getThisType() != null;
   }
 
@@ -657,8 +654,8 @@ void resolveEnums(JSTypeCreatorFromJSDoc typeParser) {
   }
 
   void finalizeScope() {
-    Preconditions.checkState(isTopLevel() || this.declaredType != null,
-        "No declared type for function-scope: %s", this.root);
+    Preconditions.checkNotNull(
+        this.declaredType, "No declared type for scope: %s", this.root);
     unknownTypeNames = ImmutableSet.of();
     // For now, we put types of namespaces directly into the locals.
     // Alternatively, we could move this into NewTypeInference.initEdgeEnvs

src/com/google/javascript/jscomp/NewTypeInference.java

@@ -550,15 +550,15 @@ private void initEdgeEnvsFwd(TypeEnv entryEnv) {
     // For function scopes, add the formal parameters and the free variables
     // from outer scopes to the environment.
     Set<String> nonLocals = new LinkedHashSet<>();
+    if (currentScope.hasThis()) {
+      nonLocals.add(THIS_ID);
+    }
     if (currentScope.isFunction()) {
       if (currentScope.getName() != null) {
         nonLocals.add(currentScope.getName());
       }
       nonLocals.addAll(currentScope.getOuterVars());
       nonLocals.addAll(currentScope.getFormals());
-      if (currentScope.hasThis()) {
-        nonLocals.add(THIS_ID);
-      }
       entryEnv = envPutType(entryEnv, RETVAL_ID, UNDEFINED);
     } else {
       nonLocals.addAll(currentScope.getExterns());
@@ -597,14 +597,14 @@ private TypeEnv getTypeEnvFromDeclaredTypes() {
     Set<String> locals = currentScope.getLocals();
     varNames.addAll(locals);
     varNames.addAll(currentScope.getExterns());
+    if (currentScope.hasThis()) {
+      varNames.add(THIS_ID);
+    }
     if (currentScope.isFunction()) {
       if (currentScope.getName() != null) {
         varNames.add(currentScope.getName());
       }
       varNames.addAll(currentScope.getFormals());
-      if (currentScope.hasThis()) {
-        varNames.add(THIS_ID);
-      }
       // In the rare case when there is a local variable named "arguments",
       // this entry will be overwritten in the foreach loop below.
       JSType argumentsType;
@@ -2300,8 +2300,8 @@ private EnvTypePair analyzeSpecializedTypeof(Node typeof, Node typeString,
 
   private EnvTypePair analyzeThisFwd(
       Node expr, TypeEnv inEnv, JSType requiredType, JSType specializedType) {
+    mayWarnAboutGlobalThis(expr, currentScope);
     if (!currentScope.hasThis()) {
-      mayWarnAboutGlobalThis(expr, currentScope);
       return new EnvTypePair(inEnv, UNKNOWN);
     }
     // A trimmed-down version of analyzeNameFwd.
@@ -2935,19 +2935,18 @@ private boolean mayWarnAboutConstProp(
     return false;
   }
 
-  private boolean mayWarnAboutGlobalThis(Node thisExpr, NTIScope currentScope) {
+  private void mayWarnAboutGlobalThis(Node thisExpr, NTIScope currentScope) {
     Preconditions.checkArgument(thisExpr.isThis());
-    Preconditions.checkState(!currentScope.hasThis());
-    Node parent = thisExpr.getParent();
-    if ((parent.isGetProp() || parent.isGetElem())
-        // Don't warn for callbacks. Most of them are not annotated but THIS is
-        // bound to a legitimate object at runtime. They do lose typechecking
-        // for THIS however, but we won't warn.
-        && !NodeUtil.isCallOrNewArgument(currentScope.getRoot())) {
-      warnings.add(JSError.make(thisExpr, GLOBAL_THIS));
-      return true;
+    if (currentScope.isTopLevel() || !currentScope.hasThis()) {
+      Node parent = thisExpr.getParent();
+      if ((parent.isGetProp() || parent.isGetElem())
+          // Don't warn for callbacks. Most of them are not annotated but THIS is
+          // bound to a legitimate object at runtime. They do lose typechecking
+          // for THIS however, but we won't warn.
+          && !NodeUtil.isCallOrNewArgument(currentScope.getRoot())) {
+        warnings.add(JSError.make(thisExpr, GLOBAL_THIS));
+      }
     }
-    return false;
   }
 
   private boolean mayWarnAboutBadIObjectIndex(Node n, JSType iobjectType,
@@ -3902,12 +3901,12 @@ private LValueResultFwd analyzeLValueFwd(
     LValueResultFwd lvalResult = null;
     switch (expr.getToken()) {
       case THIS: {
+        mayWarnAboutGlobalThis(expr, currentScope);
         if (currentScope.hasThis()) {
           lvalResult = new LValueResultFwd(inEnv, envGetType(inEnv, THIS_ID),
               currentScope.getDeclaredTypeOf(THIS_ID),
               new QualifiedName(THIS_ID));
         } else {
-          mayWarnAboutGlobalThis(expr, currentScope);
           lvalResult = new LValueResultFwd(inEnv, UNKNOWN, null, null);
         }
         break;

test/com/google/javascript/jscomp/NewTypeInferenceTest.java

@@ -17838,4 +17838,16 @@ public void testDontCrashWhenDeclaringFunctionOnScalar() {
         "}"),
         NewTypeInference.ADDING_PROPERTY_TO_NON_OBJECT);
   }
+
+  public void testDontTypeGlobalThisAsUknown() {
+    typeCheck(
+        "var /** null */ x = this;",
+        NewTypeInference.MISTYPED_ASSIGN_RHS);
+
+    typeCheck("var /** !Window */ x = this;");
+
+    typeCheck(
+        "var y = this.toString();",
+        NewTypeInference.GLOBAL_THIS);
+  }
 }