8039026: Definitely unassigned field can be accessed

Reviewed-by: vromero, jlahoda

src/share/classes/com/sun/tools/javac/code/Source.java

@@ -191,6 +191,9 @@ public enum Source {
     public boolean allowObjectToPrimitiveCast() {
         return compareTo(JDK1_7) >= 0;
     }
+    public boolean enforceThisDotInit() {
+        return compareTo(JDK1_7) >= 0;
+    }
     public boolean allowPoly() {
         return compareTo(JDK1_8) >= 0;
     }

src/share/classes/com/sun/tools/javac/comp/Flow.java

@@ -197,6 +197,7 @@ public class Flow {
     private final boolean allowImprovedRethrowAnalysis;
     private final boolean allowImprovedCatchAnalysis;
     private final boolean allowEffectivelyFinalInInnerClasses;
+    private final boolean enforceThisDotInit;
 
     public static Flow instance(Context context) {
         Flow instance = context.get(flowKey);
@@ -207,7 +208,7 @@ public class Flow {
 
     public void analyzeTree(Env<AttrContext> env, TreeMaker make) {
         new AliveAnalyzer().analyzeTree(env, make);
-        new AssignAnalyzer(log, syms, lint, names).analyzeTree(env);
+        new AssignAnalyzer(log, syms, lint, names, enforceThisDotInit).analyzeTree(env);
         new FlowAnalyzer().analyzeTree(env, make);
         new CaptureAnalyzer().analyzeTree(env, make);
     }
@@ -239,7 +240,7 @@ public class Flow {
         //related errors, which will allow for more errors to be detected
         Log.DiagnosticHandler diagHandler = new Log.DiscardDiagnosticHandler(log);
         try {
-            new AssignAnalyzer(log, syms, lint, names).analyzeTree(env);
+            new AssignAnalyzer(log, syms, lint, names, enforceThisDotInit).analyzeTree(env);
             LambdaFlowAnalyzer flowAnalyzer = new LambdaFlowAnalyzer();
             flowAnalyzer.analyzeTree(env, that, make);
             return flowAnalyzer.inferredThrownTypes;
@@ -289,6 +290,7 @@ public class Flow {
         allowImprovedRethrowAnalysis = source.allowImprovedRethrowAnalysis();
         allowImprovedCatchAnalysis = source.allowImprovedCatchAnalysis();
         allowEffectivelyFinalInInnerClasses = source.allowEffectivelyFinalInInnerClasses();
+        enforceThisDotInit = source.enforceThisDotInit();
     }
 
     /**
@@ -1427,6 +1429,8 @@ public class Flow {
 
         protected Names names;
 
+        final boolean enforceThisDotInit;
+
         public static class AbstractAssignPendingExit extends BaseAnalyzer.PendingExit {
 
             final Bits inits;
@@ -1449,7 +1453,7 @@ public class Flow {
             }
         }
 
-        public AbstractAssignAnalyzer(Bits inits, Symtab syms, Names names) {
+        public AbstractAssignAnalyzer(Bits inits, Symtab syms, Names names, boolean enforceThisDotInit) {
             this.inits = inits;
             uninits = new Bits();
             uninitsTry = new Bits();
@@ -1459,6 +1463,7 @@ public class Flow {
             uninitsWhenFalse = new Bits(true);
             this.syms = syms;
             this.names = names;
+            this.enforceThisDotInit = enforceThisDotInit;
         }
 
         private boolean isInitialConstructor = false;
@@ -2280,12 +2285,34 @@ public class Flow {
 
         public void visitAssign(JCAssign tree) {
             JCTree lhs = TreeInfo.skipParens(tree.lhs);
-            if (!(lhs instanceof JCIdent)) {
+            if (!isIdentOrThisDotIdent(lhs))
                 scanExpr(lhs);
-            }
             scanExpr(tree.rhs);
             letInit(lhs);
         }
+        private boolean isIdentOrThisDotIdent(JCTree lhs) {
+            if (lhs.hasTag(IDENT))
+                return true;
+            if (!lhs.hasTag(SELECT))
+                return false;
+
+            JCFieldAccess fa = (JCFieldAccess)lhs;
+            return fa.selected.hasTag(IDENT) &&
+                   ((JCIdent)fa.selected).name == names._this;
+        }
+
+        // check fields accessed through this.<field> are definitely
+        // assigned before reading their value
+        public void visitSelect(JCFieldAccess tree) {
+            super.visitSelect(tree);
+            if (enforceThisDotInit &&
+                tree.selected.hasTag(IDENT) &&
+                ((JCIdent)tree.selected).name == names._this &&
+                tree.sym.kind == VAR)
+            {
+                checkInit(tree.pos(), (VarSymbol)tree.sym);
+            }
+        }
 
         public void visitAssignop(JCAssignOp tree) {
             scanExpr(tree.lhs);
@@ -2419,8 +2446,8 @@ public class Flow {
             }
         }
 
-        public AssignAnalyzer(Log log, Symtab syms, Lint lint, Names names) {
-            super(new Bits(), syms, names);
+        public AssignAnalyzer(Log log, Symtab syms, Lint lint, Names names, boolean enforceThisDotInit) {
+            super(new Bits(), syms, names, enforceThisDotInit);
             this.log = log;
             this.lint = lint;
         }

src/share/classes/com/sun/tools/javac/jvm/Gen.java

 /*
- * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 2014, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -2818,7 +2818,7 @@ public class Gen extends JCTree.Visitor {
         }
 
         private LVTAssignAnalyzer(LVTRanges lvtRanges, Symtab syms, Names names) {
-            super(new LVTBits(), syms, names);
+            super(new LVTBits(), syms, names, false);
             lvtInits = (LVTBits)inits;
             this.lvtRanges = lvtRanges;
         }

test/tools/javac/DefiniteAssignment/T8039026.java

+/*
+ * @test /nodynamiccopyright/
+ * @bug 8039026
+ * @summary Definitely unassigned field can be accessed
+ * @compile/fail/ref=T8039026.out -XDrawDiagnostics T8039026.java
+ */
+
+public class T8039026 {
+    final int x,y,z;
+    final int a = this.y;  // <- error
+    {
+        int b = true ? this.x : 0;  // <- error
+        System.out.println(this.x); // <- error
+        this.y = 1;
+    }
+    T8039026() {
+        this.x = 1;      // <- no error!
+        this.y = 1;      // <- error
+        this.z = this.x; // <- no error
+    }
+}

test/tools/javac/DefiniteAssignment/T8039026.out

+T8039026.java:10:23: compiler.err.var.might.not.have.been.initialized: y
+T8039026.java:12:28: compiler.err.var.might.not.have.been.initialized: x
+T8039026.java:18:13: compiler.err.var.might.already.be.assigned: y
+3 errors