Made check more readable

Author: Arthur Ozga

src/compiler/checker.ts

@@ -4875,17 +4875,19 @@ namespace ts {
  let targetReturnType = getReturnTypeOfSignature(target);
  if (targetReturnType === voidType) return result;
  let sourceReturnType = getReturnTypeOfSignature(source);
- 
- let targetReturnDecl = targetReturnType.symbol && getDeclarationOfKind(targetReturnType.symbol, SyntaxKind.ClassDeclaration);
+
  let sourceReturnDecl = sourceReturnType.symbol && getDeclarationOfKind(sourceReturnType.symbol, SyntaxKind.ClassDeclaration);
- 
- if(sourceReturnDecl && sourceReturnDecl.flags & NodeFlags.Abstract && (!targetReturnDecl || !(targetReturnDecl.flags & NodeFlags.Abstract))) {
- if(reportErrors) {
+ let targetReturnDecl = targetReturnType.symbol && getDeclarationOfKind(targetReturnType.symbol, SyntaxKind.ClassDeclaration);
+ let sourceIsAbstract = sourceReturnDecl && sourceReturnDecl.flags & NodeFlags.Abstract;
+ let targetIsAbstract = targetReturnDecl && targetReturnDecl.flags & NodeFlags.Abstract;
+
+ if (sourceIsAbstract && !targetIsAbstract) {
+ if (reportErrors) {
  reportError(Diagnostics.Cannot_assign_an_abstract_constructor_type_to_a_non_abstract_constructor_type);
  }
  return Ternary.False;
  }
- 
+
  return result & isRelatedTo(sourceReturnType, targetReturnType, reportErrors);
  }