Further fixes in overlap checking.

Rhss of code dispatching on overlapping structs are no longer
considered dead, and as such, are now typechecked.

Had to fix a test that passed only because some not-really-dead code
was not being typechecked.

original commit: 4d5b50dee9e04aee167a7e04fbbe23526131fcad

collects/tests/typed-scheme/fail/dead-substruct.rkt

@@ -0,0 +1,16 @@
+#;
+(exn-pred 1)
+#lang typed/scheme
+
+(define-struct: parent ((x : Integer)))
+(define-struct: (child1 parent) ((y : Integer)))
+(define-struct: (child2 parent) ((y : Float)))
+
+(: f (parent -> Integer))
+(define (f x)
+  (cond [(child1? x) (+ "a" "b")] ; rhs was considered dead code
+        [(child2? x) 2]
+        [else (error "eh?")]))
+
+(f (make-child1 1 2))
+(f (make-child2 1 2.0))

collects/tests/typed-scheme/optimizer/generic/dead-substructs.rkt

@@ -0,0 +1,17 @@
+#lang typed/scheme #:optimize
+
+;; originally from nucleic3
+;; cond on substructs, branches were considered dead
+
+(define-struct: parent ((x : Integer)))
+(define-struct: (child1 parent) ((y : Integer)))
+(define-struct: (child2 parent) ((y : Float)))
+
+(: f (parent -> Integer))
+(define (f x)
+  (cond [(child1? x) 1]
+        [(child2? x) 2]
+        [else (error "eh?")]))
+
+(f (make-child1 1 2))
+(f (make-child2 1 2.0))

collects/tests/typed-scheme/succeed/priority-queue.scm

@@ -65,15 +65,15 @@
 ;; "bug" found - handling of empty heaps
 (pdefine: (a) (find-min [pq : (priority-queue a)]) : a 
 	  (let ([h (heap pq)])
-	    (if (heap:heap-node? h)
-		(elm (heap:find-min h))
-		(error "priority queue empty"))))
+            (if (heap:empty? h)
+                (error "priority queue empty")
+                (elm (heap:find-min h)))))
 
 (pdefine: (a) (find-min-priority [pq : (priority-queue a)]) : number
 	  (let ([h (heap pq)])
-	    (if (heap:heap-node? h)
-		(pri (heap:find-min h))
-		(error "priority queue empty"))))
+	    (if (heap:empty? h)
+		(error "priority queue empty")
+                (pri (heap:find-min h)))))
 
 (pdefine: (a) (insert [x : a] [p : number] [pq : (priority-queue a)]) : (priority-queue a)
 	  (make (heap:insert (cons p x) (heap pq))))
@@ -84,9 +84,9 @@
 
 (pdefine: (a) (delete-min [pq : (priority-queue a)]) : (priority-queue a)
 	  (let ([h (heap pq)])
-	    (if (heap:heap-node? h)
-		(make (heap:delete-min h))
-		(error "priority queue empty"))))
+	    (if (heap:empty? h)
+                (error "priority queue empty")
+		(make (heap:delete-min h)))))
 
 
 (pdefine: (a) (size [pq : (priority-queue a)]) : number

collects/typed-scheme/types/remove-intersect.rkt

@@ -24,7 +24,8 @@
          [(list (F: _) _) #t]
          [(list _ (F: _)) #t]
          [(list (Name: n) (Name: n*)) 
-          (overlap (resolve-once t1) (resolve-once t2))]
+          (or (free-identifier=? n n*)
+              (overlap (resolve-once t1) (resolve-once t2)))]
          [(list (? Mu?) _) (overlap (unfold t1) t2)]
          [(list _ (? Mu?)) (overlap t1 (unfold t2))]
          [(list (Union: e) t)
@@ -73,8 +74,8 @@
                 (and t2 (Struct: n* p* flds* _ _ _ _ _)))
           (let ([p1 (if (Name? p) (resolve-name p) p)]
                 [p2 (if (Name? p*) (resolve-name p*) p*)])
-            (or (overlap t1 p2)
-                (overlap t2 p1)
+            (or (and p2 (overlap t1 p2))
+                (and p1 (overlap t2 p1))
                 (and (= (length flds) (length flds*)) 
                      (for/and ([f flds] [f* flds*]) 
                        (match* (f f*)