Cleanup: use TypeSwitchStmt.getAssign, not a raw child accessor

Author: smowton

ql/src/semmle/go/Stmt.qll

@@ -882,6 +882,9 @@ class TypeSwitchStmt extends @typeswitchstmt, SwitchStmt {
   /** Gets the assign statement of this type-switch statement. */
   SimpleAssignStmt getAssign() { result = getChildStmt(1) }
 
+  /** Gets the test statement of this type-switch statement. This is a `SimpleAssignStmt` or `ExprStmt`. */
+  Stmt getTest() { result = getChildStmt(1) }
+
   /** Gets the expression whose type is examined by this `switch` statement. */
   Expr getExpr() { result = getAssign().getRhs() or result = getChildStmt(1).(ExprStmt).getExpr() }
 

ql/src/semmle/go/controlflow/ControlFlowGraphImpl.qll

@@ -1761,7 +1761,7 @@ module CFG {
         or
         first = MkImplicitTrue(this)
         or
-        firstNode(this.(TypeSwitchStmt).getChildStmt(1), first)
+        firstNode(this.(TypeSwitchStmt).getTest(), first)
       )
     }
 
@@ -1775,7 +1775,7 @@ module CFG {
         last = MkImplicitTrue(this) and
         cmpl = Bool(true)
         or
-        lastNode(this.(TypeSwitchStmt).getChildStmt(1), last, cmpl)
+        lastNode(this.(TypeSwitchStmt).getTest(), last, cmpl)
       ) and
       (
         not cmpl.isNormal()
@@ -1811,13 +1811,13 @@ module CFG {
       (
         firstNode(this.(ExpressionSwitchStmt).getExpr(), succ) or
         succ = MkImplicitTrue(this) or
-        firstNode(this.(TypeSwitchStmt).getChildStmt(1), succ)
+        firstNode(this.(TypeSwitchStmt).getTest(), succ)
       )
       or
       (
         lastNode(this.(ExpressionSwitchStmt).getExpr(), pred, normalCompletion()) or
         pred = MkImplicitTrue(this) or
-        lastNode(this.(TypeSwitchStmt).getChildStmt(1), pred, normalCompletion())
+        lastNode(this.(TypeSwitchStmt).getTest(), pred, normalCompletion())
       ) and
       (
         firstNode(getNonDefaultCase(0), succ)