Move to isBooleanConstant

Author: JarLob

csharp/ql/lib/semmle/code/csharp/controlflow/internal/Completion.qll

@@ -199,6 +199,17 @@ private predicate isBooleanConstant(Expr e, boolean value) {
     value = false
     or
     isConstantComparison(e, value)
+    or
+    exists(Method m, Call c, Expr expr |
+      m = any(SystemStringClass s).getIsNullOrEmptyMethod() and
+      c.getTarget() = m and
+      e = c and
+      expr = c.getArgument(0) and
+      expr.hasValue() and
+      if expr.getValue().length() > 0 and not expr instanceof NullLiteral
+      then value = false
+      else value = true
+    )
   )
 }
 

csharp/ql/src/Bad Practices/Control-Flow/ConstantCondition.ql

@@ -73,30 +73,6 @@ class ConstantIfCondition extends ConstantBooleanCondition {
   }
 }
 
-/** A constant return value from a function with constant input expression. */
-class ConstantReturnValueCondition extends ConstantCondition {
-  boolean b;
-
-  ConstantReturnValueCondition() {
-    exists(Method m, Call c, Expr expr |
-      m = any(SystemStringClass s).getIsNullOrEmptyMethod() and
-      c.getTarget() = m and
-      this = c and
-      expr = c.getArgument(0) and
-      expr.hasValue() and
-      if expr.getValue().length() > 0 and not expr instanceof NullLiteral
-      then b = false
-      else b = true
-    )
-  }
-
-  override string getMessage() {
-    if b = true
-    then result = "Expression is always 'true'."
-    else result = "Expression is always 'false'."
-  }
-}
-
 /** A constant loop condition. */
 class ConstantLoopCondition extends ConstantBooleanCondition {
   ConstantLoopCondition() { this = any(LoopStmt ls).getCondition() }

csharp/ql/test/query-tests/Bad Practices/Control-Flow/ConstantCondition/ConstantCondition.expected

@@ -19,10 +19,10 @@
 | ConstantIfCondition.cs:11:17:11:29 | ... == ... | Condition always evaluates to 'true'. |
 | ConstantIfCondition.cs:14:17:14:21 | false | Condition always evaluates to 'false'. |
 | ConstantIfCondition.cs:17:17:17:26 | ... == ... | Condition always evaluates to 'true'. |
-| ConstantIsNullOrEmpty.cs:10:21:10:54 | call to method IsNullOrEmpty | Expression is always 'false'. |
-| ConstantIsNullOrEmpty.cs:46:21:46:46 | call to method IsNullOrEmpty | Expression is always 'true'. |
-| ConstantIsNullOrEmpty.cs:50:21:50:44 | call to method IsNullOrEmpty | Expression is always 'true'. |
-| ConstantIsNullOrEmpty.cs:54:21:54:45 | call to method IsNullOrEmpty | Expression is always 'false'. |
+| ConstantIsNullOrEmpty.cs:10:21:10:54 | call to method IsNullOrEmpty | Condition always evaluates to 'false'. |
+| ConstantIsNullOrEmpty.cs:46:21:46:46 | call to method IsNullOrEmpty | Condition always evaluates to 'true'. |
+| ConstantIsNullOrEmpty.cs:50:21:50:44 | call to method IsNullOrEmpty | Condition always evaluates to 'true'. |
+| ConstantIsNullOrEmpty.cs:54:21:54:45 | call to method IsNullOrEmpty | Condition always evaluates to 'false'. |
 | ConstantNullCoalescingLeftHandOperand.cs:11:24:11:34 | access to constant NULL_OBJECT | Expression is never 'null'. |
 | ConstantNullCoalescingLeftHandOperand.cs:12:24:12:27 | null | Expression is always 'null'. |
 | ConstantWhileCondition.cs:12:20:12:32 | ... == ... | Condition always evaluates to 'true'. |