[ConstraintSystem] Add a special locator element for implicit @dynamicCallable calls

Author: xedin

lib/Sema/ConstraintLocator.cpp

@@ -113,6 +113,7 @@ unsigned LocatorPathElt::getNewSummaryFlags() const {
   case ConstraintLocator::KeyPathValue:
   case ConstraintLocator::KeyPathComponentResult:
   case ConstraintLocator::Condition:
+  case ConstraintLocator::DynamicCallable:
     return 0;
 
   case ConstraintLocator::FunctionArgument:
@@ -453,6 +454,10 @@ void ConstraintLocator::dump(SourceManager *sm, raw_ostream &out) const {
     case Condition:
       out << "condition expression";
       break;
+
+    case DynamicCallable:
+      out << "implicit call to @dynamicCallable method";
+      break;
     }
   }
   out << ']';

lib/Sema/ConstraintLocatorPathElts.def

@@ -167,6 +167,8 @@ CUSTOM_LOCATOR_PATH_ELT(Witness)
 /// The condition associated with 'if' expression or ternary operator.
 SIMPLE_LOCATOR_PATH_ELT(Condition)
 
+SIMPLE_LOCATOR_PATH_ELT(DynamicCallable)
+
 #undef LOCATOR_PATH_ELT
 #undef CUSTOM_LOCATOR_PATH_ELT
 #undef SIMPLE_LOCATOR_PATH_ELT

lib/Sema/ConstraintSystem.cpp

@@ -3066,6 +3066,11 @@ void constraints::simplifyLocator(Expr *&anchor,
       break;
     }
 
+    case ConstraintLocator::DynamicCallable: {
+      path = path.slice(1);
+      continue;
+    }
+
     case ConstraintLocator::ApplyFunction:
       // Extract application function.
       if (auto applyExpr = dyn_cast<ApplyExpr>(anchor)) {