Formatted parameters always a variadic parameter

Author: owen-mc

go/ql/lib/semmle/go/StringOps.qll

@@ -304,11 +304,6 @@ module StringOps {
        * Gets the parameter index of the format string.
        */
       abstract int getFormatStringIndex();
-
-      /**
-       * Gets the parameter index of the first parameter to be formatted.
-       */
-      abstract int getFirstFormattedParameterIndex();
     }
 
     /**
@@ -336,7 +331,7 @@ module StringOps {
         formatDirective = this.getComponent(n) and
         formatDirective.charAt(0) = "%" and
         formatDirective.charAt(1) != "%" and
-        result = this.getArgument((n / 2) + f.getFirstFormattedParameterIndex())
+        result = this.getImplicitVarargsArgument((n / 2))
       }
     }
   }

go/ql/lib/semmle/go/frameworks/ElazarlGoproxy.qll

@@ -112,8 +112,6 @@ module ElazarlGoproxy {
     ProxyLogFunction() { this.hasQualifiedName(packagePath(), "ProxyCtx", ["Logf", "Warnf"]) }
 
     override int getFormatStringIndex() { result = 0 }
-
-    override int getFirstFormattedParameterIndex() { result = 1 }
   }
 
   private class ProxyLog extends LoggerCall::Range, DataFlow::MethodCallNode {

go/ql/lib/semmle/go/frameworks/Glog.qll

@@ -39,8 +39,6 @@ module Glog {
     StringFormatter() { this.getName().matches("%f") }
 
     override int getFormatStringIndex() { result = super.getFirstPrintedArg() }
-
-    override int getFirstFormattedParameterIndex() { result = super.getFirstPrintedArg() + 1 }
   }
 
   private class GlogCall extends LoggerCall::Range, DataFlow::CallNode {

go/ql/lib/semmle/go/frameworks/Logrus.qll

@@ -43,7 +43,5 @@ module Logrus {
     }
 
     override int getFormatStringIndex() { result = argOffset }
-
-    override int getFirstFormattedParameterIndex() { result = argOffset + 1 }
   }
 }

go/ql/lib/semmle/go/frameworks/Spew.qll

@@ -31,8 +31,6 @@ module Spew {
     StringFormatter() { this.getName().matches("%f") }
 
     override int getFormatStringIndex() { result = super.getFirstPrintedArg() }
-
-    override int getFirstFormattedParameterIndex() { result = super.getFirstPrintedArg() + 1 }
   }
 
   private class SpewCall extends LoggerCall::Range, DataFlow::CallNode {

go/ql/lib/semmle/go/frameworks/Zap.qll

@@ -32,8 +32,6 @@ module Zap {
     ZapFormatter() { this.getName().matches("%f") }
 
     override int getFormatStringIndex() { result = 0 }
-
-    override int getFirstFormattedParameterIndex() { result = 1 }
   }
 
   /**

go/ql/lib/semmle/go/frameworks/stdlib/Fmt.qll

@@ -66,8 +66,6 @@ module Fmt {
     }
 
     override int getFormatStringIndex() { result = argOffset }
-
-    override int getFirstFormattedParameterIndex() { result = argOffset + 1 }
   }
 
   /** The `Sscan` function or one of its variants. */

go/ql/lib/semmle/go/frameworks/stdlib/Log.qll

@@ -20,8 +20,6 @@ module Log {
     LogFormatter() { this.getName().matches("%f") }
 
     override int getFormatStringIndex() { result = 0 }
-
-    override int getFirstFormattedParameterIndex() { result = 1 }
   }
 
   private class LogCall extends LoggerCall::Range, DataFlow::CallNode {