Implement (most of) option openjdk#2 from discussion in PR openjdk#25664.

There is still one test failure (SourceTreeScannerTest.java).

Author: archiecobbs

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

@@ -5717,9 +5717,9 @@ private Type capture(Type type) {
     private void setSyntheticVariableType(JCVariableDecl tree, Type type) {
         if (type.isErroneous()) {
             tree.vartype = make.at(tree.pos()).Erroneous();
-        } else if (tree.declaredUsingVar()) {       // set the type's start and end positions to match the "var" keyword
+        } else if (tree.declaredUsingVar()) {
             Assert.check(tree.typePos != Position.NOPOS);
-            tree.vartype = make.at(tree.typePos, tree.typePos + names.var.length(), env.toplevel.endPositions).Type(type);
+            tree.vartype = make.at(tree.typePos).Type(type);
         } else {
             tree.vartype = make.at(tree.pos()).Type(type);
         }

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

@@ -463,15 +463,7 @@ public String toString() {
     /** Set position field and return this tree.
      */
     public JCTree setPos(int pos) {
-        return setPos(pos, Position.NOPOS, null);
-    }
-
-    /** Set start and end position and return this tree.
-     */
-    public JCTree setPos(int pos, int endPos, EndPosTable endPosTable) {
         this.pos = pos;
-        if (endPos != Position.NOPOS && endPosTable != null)
-            endPosTable.storeEnd(this, endPos);
         return this;
     }
 
@@ -1091,7 +1083,13 @@ public boolean declaredUsingVar() {
         @DefinedBy(Api.COMPILER_TREE)
         public JCExpression getNameExpression() { return nameexpr; }
         @DefinedBy(Api.COMPILER_TREE)
-        public JCTree getType() { return vartype; }
+        public JCTree getType() {
+            return switch (declKind) {
+                case EXPLICIT -> vartype;
+                case IMPLICIT -> null;
+                case VAR -> name != null ? new JCIdent(name.table.names.var, sym) : null;
+            };
+        }
         @DefinedBy(Api.COMPILER_TREE)
         public JCExpression getInitializer() {
             return init;