QL: make the alert-message more precise when the type-cast is also redundant

Author: erik-krogh

ql/ql/src/queries/style/CouldBeCast.ql

@@ -11,13 +11,17 @@
 import ql
 import codeql_ql.style.CouldBeCastQuery
 
-from AstNode aggr, VarDecl var, string msg
+from AstNode aggr, VarDecl var, string msg, Expr operand
 where
-  exists(string kind | aggregateCouldBeCast(aggr, _, kind, var, _) |
+  exists(string kind | aggregateCouldBeCast(aggr, _, kind, var, operand) |
     kind = "exists" and
-    msg = "The assignment to $@ in the exists(..) can replaced with an instanceof expression."
+    if operand.getType().getASuperType*() = var.getType()
+    then msg = "The assignment in the exists(..) is redundant."
+    else msg = "The assignment to $@ in the exists(..) can replaced with an instanceof expression."
     or
     kind = "any" and
-    msg = "The assignment to $@ in this any(..) can be replaced with an inline cast."
+    if operand.getType().getASuperType*() = var.getType()
+    then msg = "The assignment in the any(..) is redundant."
+    else msg = "The assignment to $@ in this any(..) can be replaced with an inline cast."
   )
 select aggr, msg, var, var.getName()

ql/ql/test/queries/style/CouldBeCast/CouldBeCast.expected

@@ -1,3 +1,5 @@
 | Foo.qll:3:3:3:24 | Exists | The assignment to $@ in the exists(..) can replaced with an instanceof expression. | Foo.qll:3:10:3:15 | j | j |
 | Foo.qll:7:3:7:21 | Any | The assignment to $@ in this any(..) can be replaced with an inline cast. | Foo.qll:7:7:7:12 | j | j |
 | Foo.qll:9:3:9:25 | Any | The assignment to $@ in this any(..) can be replaced with an inline cast. | Foo.qll:9:7:9:12 | j | j |
+| Foo.qll:15:3:15:20 | Any | The assignment in the any(..) is redundant. | Foo.qll:15:7:15:11 | j | j |
+| Foo.qll:17:3:17:23 | Exists | The assignment in the exists(..) is redundant. | Foo.qll:17:10:17:14 | j | j |

ql/ql/test/queries/style/CouldBeCast/Foo.qll

@@ -11,6 +11,10 @@ predicate foo(int i) {
   any(Even j | j = i | j * 2) = 4 // OK
   or
   any(Even j | j = i and j % 4 = 0 | j) = 4 // OK
+  or
+  any(int j | j = i) = 2 // NOT OK
+  or
+  exists(int j | j = i) // NOT OK
 }
 
 class Even extends int {