FINALLY! Found the cause of a really weird eclipse bug,

where _ANY_ mention of com.sun.tools.javac.tree.TreeMaker,
anywhere in a source file, would disable pretty much every
intelligent part of what makes the 'I' in IDE in eclipse:
No auto-complete, no 'go to declaration', etcetera, but only
since Eclipse Juno (not fixed in Kepler either). It's the
presence of src/stubs/com/sun/tools/javac/util/Context.java.

I've moved Context to a special stubs directory that's only used
for javac (so that we still get the benefit of getting some
warnings and such when making command line builds), and removed
the @Override annotations for where the stubbing is relevant
(for methods that exist in javac7 but not in javac6 on interfaces
we create implementations of). Furthermore, I did some extremely
tricky work in making our version actuall compatible with the
exact class signatures of both javac6- and javac7+'s versions;
generation of synthetic methods for reified type parameters was
causing havoc.

A big stack of 'here be voodoo' comments unfortunately added to
explain it all; necessary evil.

build.xml

@@ -147,6 +147,7 @@ the common tasks and can be called on to run the main aspects of all the sub-scr
 		</ivy:compile>
 		<ivy:compile destdir="build/stubs" source="1.5" target="1.5" includeantruntime="false">
 			<src path="src/stubs" />
+			<src path="src/javac-only-stubs" />
 			<classpath location="build/stubsstubs" />
 		</ivy:compile>
 		

src/utils/lombok/javac/java6/CommentCollectingScannerFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2011 The Project Lombok Authors.
+ * Copyright (C) 2011-2013 The Project Lombok Authors.
  * 
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -28,14 +28,33 @@ import com.sun.tools.javac.util.Context;
 
 public class CommentCollectingScannerFactory extends Scanner.Factory {
 	
+	@SuppressWarnings("all")
 	public static void preRegister(final Context context) {
 		if (context.get(scannerFactoryKey) == null) {
-			context.put(scannerFactoryKey, new Context.Factory<Scanner.Factory>() {
-				public CommentCollectingScanner.Factory make() {
+			// Careful! There is voodoo magic here!
+			//
+			// Context.Factory is parameterized. make() is for javac6 and below; make(Context) is for javac7 and up.
+			// this anonymous inner class definition is intentionally 'raw' - the return type of both 'make' methods is 'T',
+			// which means the compiler will only generate the correct "real" override method (with returntype Object, which is
+			// the lower bound for T, as a synthetic accessor for the make with returntype ScannerFactory) for that make method which
+			// is actually on the classpath (either make() for javac6-, or make(Context) for javac7+).
+			//
+			// We normally solve this issue via src/stubs, with BOTH make methods listed, but for some reason the presence of a stubbed out
+			// Context (or even a complete copy, it doesn't matter) results in a really strange eclipse bug, where any mention of any kind
+			// of com.sun.tools.javac.tree.TreeMaker in a source file disables ALL usage of 'go to declaration' and auto-complete in the entire
+			// source file.
+			//
+			// Thus, in short:
+			// * Do NOT parameterize the anonymous inner class literal.
+			// * Leave the return types as 'j.l.Object'.
+			// * Leave both make methods intact; deleting one has no effect on javac6- / javac7+, but breaks the other. Hard to test for.
+			// * Do not stub com.sun.tools.javac.util.Context or any of its inner types, like Factory.
+			context.put(scannerFactoryKey, new Context.Factory() {
+				public Object make() {
 					return new CommentCollectingScannerFactory(context);
 				}
 				
-				public CommentCollectingScanner.Factory make(Context c) {
+				public Object make(Context c) {
 					return new CommentCollectingScannerFactory(c);
 				}
 			});

src/utils/lombok/javac/java7/CommentCollectingScannerFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2011 The Project Lombok Authors.
+ * Copyright (C) 2011-2013 The Project Lombok Authors.
  * 
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -29,14 +29,35 @@ import com.sun.tools.javac.util.Context;
 
 public class CommentCollectingScannerFactory extends ScannerFactory {
 	
+	@SuppressWarnings("all")
 	public static void preRegister(final Context context) {
 		if (context.get(scannerFactoryKey) == null) {
-			context.put(scannerFactoryKey, new Context.Factory<ScannerFactory>() {
-				public ScannerFactory make() {
+			// Careful! There is voodoo magic here!
+			//
+			// Context.Factory is parameterized. make() is for javac6 and below; make(Context) is for javac7 and up.
+			// this anonymous inner class definition is intentionally 'raw' - the return type of both 'make' methods is 'T',
+			// which means the compiler will only generate the correct "real" override method (with returntype Object, which is
+			// the lower bound for T, as a synthetic accessor for the make with returntype ScannerFactory) for that make method which
+			// is actually on the classpath (either make() for javac6-, or make(Context) for javac7+).
+			//
+			// We normally solve this issue via src/stubs, with BOTH make methods listed, but for some reason the presence of a stubbed out
+			// Context (or even a complete copy, it doesn't matter) results in a really strange eclipse bug, where any mention of any kind
+			// of com.sun.tools.javac.tree.TreeMaker in a source file disables ALL usage of 'go to declaration' and auto-complete in the entire
+			// source file.
+			//
+			// Thus, in short:
+			// * Do NOT parameterize the anonymous inner class literal.
+			// * Leave the return types as 'j.l.Object'.
+			// * Leave both make methods intact; deleting one has no effect on javac6- / javac7+, but breaks the other. Hard to test for.
+			// * Do not stub com.sun.tools.javac.util.Context or any of its inner types, like Factory.
+			context.put(scannerFactoryKey, new Context.Factory() {
+				// This overrides the javac6- version of make.
+				public Object make() {
 					return new CommentCollectingScannerFactory(context);
 				}
 				
-				@Override public ScannerFactory make(Context c) {
+				// This overrides the javac7+ version.
+				public Object make(Context c) {
 					return new CommentCollectingScannerFactory(c);
 				}
 			});