Java: Improve precision of SuccessorType labels in CFG.

Author: aschackmull

java/ql/lib/semmle/code/java/ControlFlowGraph.qll

@@ -82,6 +82,7 @@ module;
  */
 
 import java
+private import codeql.controlflow.SuccessorType
 private import codeql.util.Boolean
 private import Completion
 private import controlflow.internal.Preconditions
@@ -124,6 +125,28 @@ module ControlFlow {
       result = succ(this, NormalCompletion())
     }
 
+    /** Gets an immediate successor of this node of a given type, if any. */
+    Node getASuccessor(SuccessorType t) {
+      result = branchSuccessor(this, t.(BooleanSuccessor).getValue())
+      or
+      exists(Completion completion |
+        result = succ(this, completion) and
+        not result = branchSuccessor(this, _)
+      |
+        completion = NormalCompletion() and t instanceof DirectSuccessor
+        or
+        completion = ReturnCompletion() and t instanceof ReturnSuccessor
+        or
+        completion = BreakCompletion(_) and t instanceof BreakSuccessor
+        or
+        completion = YieldCompletion(_) and t instanceof BreakSuccessor
+        or
+        completion = ContinueCompletion(_) and t instanceof ContinueSuccessor
+        or
+        completion = ThrowCompletion(_) and t instanceof ExceptionSuccessor
+      )
+    }
+
     /** Gets the basic block that contains this node. */
     BasicBlock getBasicBlock() { result.getANode() = this }
 

java/ql/lib/semmle/code/java/controlflow/BasicBlocks.qll

@@ -22,20 +22,8 @@ private module Input implements BB::InputSig<Location> {
   /** Gets the CFG scope in which this node occurs. */
   CfgScope nodeGetCfgScope(Node node) { node.getEnclosingCallable() = result }
 
-  private Node getASpecificSuccessor(Node node, SuccessorType t) {
-    node.(ConditionNode).getABranchSuccessor(t.(BooleanSuccessor).getValue()) = result
-    or
-    node.getAnExceptionSuccessor() = result and t instanceof ExceptionSuccessor
-  }
-
   /** Gets an immediate successor of this node. */
-  Node nodeGetASuccessor(Node node, SuccessorType t) {
-    result = getASpecificSuccessor(node, t)
-    or
-    node.getASuccessor() = result and
-    t instanceof DirectSuccessor and
-    not result = getASpecificSuccessor(node, _)
-  }
+  Node nodeGetASuccessor(Node node, SuccessorType t) { result = node.getASuccessor(t) }
 
   /**
    * Holds if `node` represents an entry node to be used when calculating