[CSStep] Add message to list possible type variables that will be attempted next.

Author: Amritpan Kaur

lib/Sema/CSStep.cpp

@@ -370,6 +370,21 @@ StepResult ComponentStep::take(bool prevFailed) {
       log.indent(2);
       log << ")" << '\n';
       log.indent(0);
+      
+      if (CS.getTypeVariables().size() > 1) {
+        auto &log = getDebugLogger();
+        log << "(selecting next type variable to attempt from [";
+        auto typeVars = CS.getTypeVariables();
+        PrintOptions PO;
+        PO.PrintTypesForDebugging = true;
+        interleave(typeVars, [&](TypeVariableType *typeVar) {
+                     Type(typeVar).print(log, PO);
+                   },
+                   [&] {
+                     log << ", ";
+                   });
+        log << "])" << '\n';
+      }
     }
   }