Stage 1 for a workaround for ooc-lang#239/ooc-lang#311: A warning for…

… varargs-inside-ternary-expressions-or-boolean-binaryops.

source/rock/middle/FunctionCall.ooc

@@ -4,7 +4,7 @@ import Visitor, Expression, FunctionDecl, Argument, Type, VariableAccess,
        TypeDecl, Node, VariableDecl, AddressOf, CommaSequence, BinaryOp,
        InterfaceDecl, Cast, NamespaceDecl, BaseType, FuncType, Return,
        TypeList, Scope, Block, InlineContext, StructLiteral, NullLiteral,
-       IntLiteral
+       IntLiteral, Ternary
 import tinker/[Response, Resolver, Trail, Errors]
 
 /**
@@ -816,6 +816,24 @@ FunctionCall: class extends Expression {
         Response OK
     }
 
+    /** print an appropriate warning if the user tries to use vararg functions in binary/ternary expressions.
+        See bug #311 for details. */
+    printVarargExpressionWarning: func (trail: Trail) {
+        i := trail getSize() - 1
+        while(i >= 0) {
+            node := trail data get(i) as Node
+            // boolean binary ops and ternary ops are the problem!
+            if((node instanceOf?(BinaryOp) && node as BinaryOp isBooleanOp()) \
+               || node instanceOf?(Ternary)) {
+                token formatMessage("Found a vararg function call inside a binary/ternary expression. Please unwrap this expression. See https://github.com/nddrylliog/rock/issues/311 for details", "WARNING") println()
+            } else if(node instanceOf?(Scope)) {
+                // we're not part of the same expression anymore!
+                break;
+            }
+            i -= 1
+        }
+    }
+
     /**
      * Resolve ooc variable arguments
      */
@@ -826,6 +844,7 @@ FunctionCall: class extends Expression {
         match (lastArg := ref args last()) {
             case vararg: VarArg =>
                 if(vararg name != null) {
+                    // ooc varargs have names!
                     numVarArgs := (args size - (ref args size - 1))
 
                     if(!args empty?()) {
@@ -874,6 +893,8 @@ FunctionCall: class extends Expression {
                         args removeAt(args lastIndex())
                     )
                     args add(VariableAccess new(vaDecl, token))
+                    // print a warning if needed
+                    printVarargExpressionWarning(trail)
                 }
         }