C#: Generalize array logic to params collection like types.

Author: michaelnebel

csharp/ql/lib/semmle/code/csharp/commons/Collections.qll

@@ -97,7 +97,8 @@ private class ParamsConstructedCollectionTypes extends ParamsCollectionTypeImpl
       unboundbase instanceof SystemCollectionsGenericIReadOnlyListTInterface or
       unboundbase instanceof SystemSpanStruct or
       unboundbase instanceof SystemReadOnlySpanStruct
-    )
+    ) and
+    not this instanceof SystemStringClass
   }
 
   override Type getElementType() { result = base.getTypeArgument(0) }

csharp/ql/lib/semmle/code/csharp/frameworks/Format.qll

@@ -250,19 +250,31 @@ class FormatCall extends MethodCall {
   /** Holds if this call has one or more insertions. */
   predicate hasInsertions() { exists(this.getArgument(this.getFirstArgument())) }
 
-  /** Holds if the arguments are supplied in an array, not individually. */
-  predicate hasArrayExpr() {
+  /**
+   * DEPRECATED: use `hasCollectionExpr` instead.
+   *
+   * Holds if the arguments are supplied in an array, not individually.
+   */
+  deprecated predicate hasArrayExpr() {
     this.getNumberOfArguments() = this.getFirstArgument() + 1 and
     this.getArgument(this.getFirstArgument()).getType() instanceof ArrayType
   }
 
+  /**
+   * Holds if the arguments are supplied in a collection, not individually.
+   */
+  predicate hasCollectionExpr() {
+    this.getNumberOfArguments() = this.getFirstArgument() + 1 and
+    this.getArgument(this.getFirstArgument()).getType() instanceof ParamsCollectionType
+  }
+
   /**
    * Gets the number of supplied arguments (excluding the format string and format
    * provider). Does not return a value if the arguments are supplied in an array,
    * in which case we generally can't assess the size of the array.
    */
   int getSuppliedArguments() {
-    not this.hasArrayExpr() and
+    not this.hasCollectionExpr() and
     result = this.getNumberOfArguments() - this.getFirstArgument()
   }