8317376: Minor improvements to the 'this' escape analyzer

Reviewed-by: vromero

make/CompileModuleTools.gmk

@@ -53,7 +53,7 @@ $(eval $(call SetupJavaCompilation, BUILD_JIGSAW_TOOLS, \
                 build/tools/jigsaw, \
     COPY := .properties .html, \
     BIN := $(TOOLS_CLASSES_DIR), \
-    DISABLED_WARNINGS := fallthrough this-escape, \
+    DISABLED_WARNINGS := fallthrough, \
     JAVAC_FLAGS := \
         --add-modules jdk.jdeps \
         --add-exports java.base/jdk.internal.module=ALL-UNNAMED \

make/modules/java.net.http/Java.gmk

@@ -1,26 +0,0 @@
-#
-# Copyright (c) 2023, 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
-# under the terms of the GNU General Public License version 2 only, as
-# published by the Free Software Foundation.  Oracle designates this
-# particular file as subject to the "Classpath" exception as provided
-# by Oracle in the LICENSE file that accompanied this code.
-#
-# This code is distributed in the hope that it will be useful, but WITHOUT
-# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
-# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
-# version 2 for more details (a copy is included in the LICENSE file that
-# accompanied this code).
-#
-# You should have received a copy of the GNU General Public License version
-# 2 along with this work; if not, write to the Free Software Foundation,
-# Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
-#
-# Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
-# or visit www.oracle.com if you need additional information or have any
-# questions.
-#
-
-DISABLED_WARNINGS_java += this-escape

make/modules/java.sql.rowset/Java.gmk

@@ -23,8 +23,6 @@
 # questions.
 #
 
-DISABLED_WARNINGS_java += this-escape
-
 DOCLINT += -Xdoclint:all/protected \
     '-Xdoclint/package:java.*,javax.*'
 CLEAN_FILES += $(wildcard \

make/modules/jdk.charsets/Java.gmk

@@ -23,6 +23,4 @@
 # questions.
 #
 
-DISABLED_WARNINGS_java += this-escape
-
 COPY += .dat

make/modules/jdk.compiler/Gendata.gmk

@@ -66,7 +66,7 @@ $(eval $(call SetupJavaCompilation, COMPILE_CREATE_SYMBOLS, \
     SRC := $(TOPDIR)/make/langtools/src/classes, \
     INCLUDES := build/tools/symbolgenerator com/sun/tools/classfile, \
     BIN := $(BUILDTOOLS_OUTPUTDIR)/create_symbols_javac, \
-    DISABLED_WARNINGS := options this-escape, \
+    DISABLED_WARNINGS := options, \
     JAVAC_FLAGS := \
         $(COMPILECREATESYMBOLS_ADD_EXPORTS), \
 ))

make/modules/jdk.crypto.ec/Java.gmk

@@ -1,26 +0,0 @@
-#
-# Copyright (c) 2023, 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
-# under the terms of the GNU General Public License version 2 only, as
-# published by the Free Software Foundation.  Oracle designates this
-# particular file as subject to the "Classpath" exception as provided
-# by Oracle in the LICENSE file that accompanied this code.
-#
-# This code is distributed in the hope that it will be useful, but WITHOUT
-# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
-# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
-# version 2 for more details (a copy is included in the LICENSE file that
-# accompanied this code).
-#
-# You should have received a copy of the GNU General Public License version
-# 2 along with this work; if not, write to the Free Software Foundation,
-# Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
-#
-# Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
-# or visit www.oracle.com if you need additional information or have any
-# questions.
-#
-
-DISABLED_WARNINGS_java += this-escape

make/modules/jdk.javadoc/Gendata.gmk

@@ -56,7 +56,7 @@ $(eval $(call SetupJavaCompilation, COMPILE_CREATE_SYMBOLS, \
         $(TOPDIR)/src/jdk.jdeps/share/classes, \
     INCLUDES := build/tools/symbolgenerator com/sun/tools/classfile, \
     BIN := $(BUILDTOOLS_OUTPUTDIR)/create_symbols_javadoc, \
-    DISABLED_WARNINGS := options this-escape, \
+    DISABLED_WARNINGS := options, \
     JAVAC_FLAGS := \
         $(INTERIM_LANGTOOLS_ARGS) \
         $(COMPILECREATESYMBOLS_ADD_EXPORTS), \

make/modules/jdk.jcmd/Java.gmk

@@ -23,6 +23,4 @@
 # questions.
 #
 
-DISABLED_WARNINGS_java += this-escape
-
 COPY += _options

make/modules/jdk.jconsole/Java.gmk

@@ -23,8 +23,6 @@
 # questions.
 #
 
-DISABLED_WARNINGS_java += this-escape
-
 COPY += .gif .png
 
 CLEAN_FILES += $(wildcard \

make/modules/jdk.jdeps/Gensrc.gmk

@@ -26,8 +26,6 @@
 include GensrcCommon.gmk
 include GensrcProperties.gmk
 
-DISABLED_WARNINGS_java += this-escape
-
 $(eval $(call SetupVersionProperties, JAVAP_VERSION, \
     com/sun/tools/javap/resources/version.properties))
 

make/modules/jdk.jdeps/Launcher.gmk

@@ -25,8 +25,6 @@
 
 include LauncherCommon.gmk
 
-DISABLED_WARNINGS_java += this-escape
-
 ################################################################################
 ## Build javap
 ################################################################################

make/modules/jdk.jdi/Java.gmk

@@ -23,8 +23,6 @@
 # questions.
 #
 
-DISABLED_WARNINGS_java += this-escape
-
 EXCLUDES += \
     com/sun/tools/example/debug/bdi \
     com/sun/tools/example/debug/event \

make/modules/jdk.jpackage/Java.gmk

@@ -23,8 +23,6 @@
 # questions.
 #
 
-DISABLED_WARNINGS_java += this-escape
-
 COPY += .gif .png .txt .spec .script .prerm .preinst \
     .postrm .postinst .list .sh .desktop .copyright .control .plist .template \
     .icns .scpt .wxs .wxl .wxi .ico .bmp .tiff .service

make/modules/jdk.localedata/Java.gmk

@@ -23,8 +23,6 @@
 # questions.
 #
 
-DISABLED_WARNINGS_java += this-escape
-
 COPY += _dict _th
 # Exclude BreakIterator classes that are just used in compile process to generate
 # data files and shouldn't go in the product

make/modules/jdk.sctp/Java.gmk

@@ -23,8 +23,6 @@
 # questions.
 #
 
-DISABLED_WARNINGS_java += this-escape
-
 # No SCTP implementation on Mac OS X or AIX. These classes should be excluded.
 SCTP_IMPL_CLASSES = \
     $(TOPDIR)/src/jdk.sctp/unix/classes/sun/nio/ch/sctp/AssociationChange.java \

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

@@ -231,7 +231,7 @@ public class Flow {
         new AssignAnalyzer().analyzeTree(env, make);
         new FlowAnalyzer().analyzeTree(env, make);
         new CaptureAnalyzer().analyzeTree(env, make);
-        new ThisEscapeAnalyzer(names, syms, types, log, lint).analyzeTree(env);
+        new ThisEscapeAnalyzer(names, syms, types, rs, log, lint).analyzeTree(env);
     }
 
     public void analyzeLambda(Env<AttrContext> env, JCLambda that, TreeMaker make, boolean speculative) {

src/jdk.compiler/share/classes/com/sun/tools/javac/tree/TreeInfo.java

@@ -182,6 +182,41 @@ public class TreeInfo {
         }
     }
 
+    /** Check if the given tree is an explicit reference to the 'this' instance of the
+     *  class currently being compiled. This is true if tree is:
+     *  - An unqualified 'this' identifier
+     *  - A 'super' identifier qualified by a class name whose type is 'currentClass' or a supertype
+     *  - A 'this' identifier qualified by a class name whose type is 'currentClass' or a supertype
+     *    but also NOT an enclosing outer class of 'currentClass'.
+     */
+    public static boolean isExplicitThisReference(Types types, Type.ClassType currentClass, JCTree tree) {
+        switch (tree.getTag()) {
+            case PARENS:
+                return isExplicitThisReference(types, currentClass, skipParens(tree));
+            case IDENT: {
+                JCIdent ident = (JCIdent)tree;
+                Names names = ident.name.table.names;
+                return ident.name == names._this || ident.name == names._super;
+            }
+            case SELECT: {
+                JCFieldAccess select = (JCFieldAccess)tree;
+                Type selectedType = types.erasure(select.selected.type);
+                if (!selectedType.hasTag(TypeTag.CLASS))
+                    return false;
+                Symbol.ClassSymbol currentClassSym = (Symbol.ClassSymbol)((Type.ClassType)types.erasure(currentClass)).tsym;
+                Symbol.ClassSymbol selectedClassSym = (Symbol.ClassSymbol)((Type.ClassType)selectedType).tsym;
+                Names names = select.name.table.names;
+                return currentClassSym.isSubClass(selectedClassSym, types) &&
+                        (select.name == names._super ||
+                        (select.name == names._this &&
+                            (currentClassSym == selectedClassSym ||
+                            !currentClassSym.isEnclosedBy(selectedClassSym))));
+            }
+            default:
+                return false;
+        }
+    }
+
     /** Is this a call to super?
      */
     public static boolean isSuperCall(JCTree tree) {

test/langtools/tools/javac/warnings/ThisEscape.java

@@ -313,7 +313,7 @@ public class ThisEscape {
                 }
             }
 
-            public class Inner2 {
+            public static class Inner2 {
                 public Inner2() {
                     new Test3().mightLeak();
                 }
@@ -585,6 +585,124 @@ public class ThisEscape {
         }
     }
 
+    // Verify 'this' escape correctly follows outer instances through member classes
+    public static class ThisEscapeOuterRef1 {
+        class Inner {
+            void foo() {
+                ThisEscapeOuterRef1.this.hashCode();
+            }
+        }
+        public ThisEscapeOuterRef1() {
+            new Inner().foo();
+        }
+    }
+
+    // Verify 'this' escape correctly follows outer instances through local classes
+    public static class ThisEscapeOuterRef2 {
+        public ThisEscapeOuterRef2() {
+            class Inner {
+                void foo() {
+                    ThisEscapeOuterRef2.this.hashCode();
+                }
+            }
+            new Inner().foo();
+        }
+    }
+
+    // Verify 'this' escape correctly follows outer instances through anonymous classes
+    public static class ThisEscapeOuterRef3 {
+        public ThisEscapeOuterRef3() {
+            new Runnable() {
+                public void run() {
+                    ThisEscapeOuterRef3.this.hashCode();    // leak here
+                }
+            }.run();
+        }
+    }
+
+    // Verify 'this' escape knows that enhanced for loops invoke iterator(), etc.
+    public static class ThisEscapeForeach1 implements Iterable<Object> {
+        public ThisEscapeForeach1() {
+            for (Object v : this)
+                v.hashCode();           // possible leak here
+        }
+        @Override
+        public final java.util.Iterator<Object> iterator() {
+            return new java.util.Iterator<Object>() {
+                @Override
+                public boolean hasNext() {
+                    return true;
+                }
+                @Override
+                public Object next() {
+                    return ThisEscapeForeach1.this;
+                }
+            };
+        }
+    }
+
+    // Verify 'this' escape tracks deferred return values
+    public static class DeferredReturn {
+
+        public DeferredReturn(int x) {
+            ((Supplier<DeferredReturn>)this::self).get().mightLeak();  // leak here
+        }
+
+        public DeferredReturn(float x) {
+            ((Supplier<DeferredReturn>)() -> this).get().mightLeak();  // leak here
+        }
+
+        private final DeferredReturn self() {
+            return this;
+        }
+
+        protected void mightLeak() {
+        }
+    }
+
+    // Verify 'this' escape properly tracks variable types
+    public static class TypeTracking {
+
+        public TypeTracking() {
+            Runnable r = new Runnable() {
+                public void run() {
+                    TypeTracking.this.mightLeak();
+                }
+            };
+            r.run();        // leak here - we know "r" has type TypeTracking$1
+        }
+
+        protected void mightLeak() {
+        }
+    }
+
+    // Verify 'this' escape doesn't warn for outer instances of anonymous classes that don't use them
+    public static class ThisEscapeOuterRef4 {
+        public ThisEscapeOuterRef4() {
+            new Runnable() {
+                public void run() {
+                    // there is no leak in here
+                }
+            }.run();
+        }
+    }
+
+    // Verify 'this' escape doesn't warn for doubly-outer instance references
+    public static class ThisEscapeDoubleOuter {
+        public class Inner1 {
+
+            public Inner1() {
+                new Inner2().foo();     // NOT a 'this' leak
+            }
+
+            class Inner2 {
+                void foo() {
+                    ThisEscapeDoubleOuter.this.hashCode();
+                }
+            }
+        }
+    }
+
     // Verify 'this' escape detection doesn't warn for sealed classes with local permits
     public static sealed class ThisEscapeSealed permits ThisEscapeSealed.Sub1, ThisEscapeSealed.Sub2 {
 

test/langtools/tools/javac/warnings/ThisEscape.out

@@ -23,4 +23,16 @@ ThisEscape.java:396:17: compiler.warn.possible.this.escape
 ThisEscape.java:401:30: compiler.warn.possible.this.escape.location
 ThisEscape.java:444:28: compiler.warn.possible.this.escape
 ThisEscape.java:473:27: compiler.warn.possible.this.escape
-25 warnings
+ThisEscape.java:596:28: compiler.warn.possible.this.escape
+ThisEscape.java:592:50: compiler.warn.possible.this.escape.location
+ThisEscape.java:608:28: compiler.warn.possible.this.escape
+ThisEscape.java:605:54: compiler.warn.possible.this.escape.location
+ThisEscape.java:619:18: compiler.warn.possible.this.escape
+ThisEscape.java:617:54: compiler.warn.possible.this.escape.location
+ThisEscape.java:627:27: compiler.warn.possible.this.escape
+ThisEscape.java:648:55: compiler.warn.possible.this.escape
+ThisEscape.java:652:55: compiler.warn.possible.this.escape
+ThisEscape.java:672:18: compiler.warn.possible.this.escape
+ThisEscape.java:669:48: compiler.warn.possible.this.escape.location
+ThisEscape.java:726:32: compiler.warn.possible.this.escape
+37 warnings