add redundant inline cast query

Author: erik-krogh

ql/src/codeql_ql/style/RedundantInlineCastQuery.qll

@@ -0,0 +1,35 @@
+import ql
+
+class RedundantInlineCast extends AstNode instanceof InlineCast {
+  Type t;
+
+  RedundantInlineCast() {
+    t = unique( | | super.getType()) and
+    (
+      // The cast is to the type the base expression already has
+      t = unique( | | super.getBase().getType())
+      or
+      // The cast is to the same type as the other expression in an equality comparison
+      exists(ComparisonFormula comp, Expr other | comp.getOperator() = "=" |
+        this = comp.getAnOperand() and
+        other = comp.getAnOperand() and
+        this != other and
+        t = unique( | | other.getType()) and
+        not other instanceof InlineCast // we don't want to risk both sides being "redundant"
+      )
+      or
+      exists(Call call, int i, Predicate target |
+        this = call.getArgument(i) and
+        target = unique( | | call.getTarget()) and
+        t = unique( | | target.getParameterType(i))
+      )
+    ) and
+    // noopt can require explicit casts
+    not exists(Annotation annon | annon = this.getEnclosingPredicate().getAnAnnotation() |
+      annon.getName() = "pragma" and
+      annon.getArgs(0).getValue() = "noopt"
+    )
+  }
+
+  TypeExpr getTypeExpr() { result = super.getTypeExpr() }
+}

ql/src/queries/style/RedundantInlineCast.ql

@@ -0,0 +1,16 @@
+/**
+ * @name Redundant inline cast
+ * @description Redundant inline casts
+ * @kind problem
+ * @problem.severity error
+ * @id ql/redundant-inline-cast
+ * @tags maintainability
+ * @precision high
+ */
+
+import ql
+import codeql_ql.style.RedundantInlineCastQuery
+
+from RedundantInlineCast cast
+select cast, "Redundant cast to $@", cast.getTypeExpr(),
+  cast.getTypeExpr().getResolvedType().getName()