Check for duplicate record type field names

README.md

@@ -47,10 +47,9 @@ We support [Dhall 15.0.0][dhall-15], including the `with` keyword and record pun
 
 We're running the [Dhall acceptance test suites][dhall-tests] for parsing, normalization,
 [CBOR][cbor] encoding and decoding, hashing, and type inference (everything except imports), and
-currently 1,139 of 1,143 tests are passing. There are three open issues that track the acceptance
+currently 1,140 of 1,143 tests are passing. There are two open issues that track the acceptance
 tests that are not passing or that we're not running yet:
-[#5](https://github.com/travisbrown/dhallj/issues/5),
-[#6](https://github.com/travisbrown/dhallj/issues/6), and
+[#5](https://github.com/travisbrown/dhallj/issues/5) and
 [#8](https://github.com/travisbrown/dhallj/issues/8).
 
 There are several known issues:

modules/core/src/main/java/org/dhallj/core/typechecking/TypeCheck.java

@@ -417,15 +417,24 @@ public final Expr onRecord(Iterable<Entry<String, Expr>> fields, int size) {
   }
 
   public final Expr onRecordType(Iterable<Entry<String, Expr>> fields, int size) {
+    // Need to check for duplicates here; see: https://github.com/travisbrown/dhallj/issues/6
+    Set<String> fieldNamesSeen = new HashSet<>(size);
+
     Universe max = Universe.TYPE;
 
     for (Entry<String, Expr> field : fields) {
+      String fieldName = field.getKey();
+
+      if (!fieldNamesSeen.add(fieldName)) {
+        throw TypeCheckFailure.makeFieldDuplicateError(fieldName);
+      }
+
       Universe universe = Universe.fromExpr(field.getValue().accept(this));
 
       if (universe != null) {
         max = max.max(universe);
       } else {
-        throw TypeCheckFailure.makeFieldTypeError(field.getKey());
+        throw TypeCheckFailure.makeFieldTypeError(fieldName);
       }
     }
 

modules/core/src/main/java/org/dhallj/core/typechecking/TypeCheckFailure.java

@@ -122,6 +122,10 @@ static TypeCheckFailure makeFieldTypeError(String fieldName) {
     return new TypeCheckFailure("Invalid field type");
   }
 
+  static TypeCheckFailure makeFieldDuplicateError(String fieldName) {
+    return new TypeCheckFailure(String.format("duplicate field: %s", fieldName));
+  }
+
   static TypeCheckFailure makeListTypeMismatchError(Expr type1, Expr type2) {
     return new TypeCheckFailure("List elements should all have the same type");
   }

tests/src/test/scala/org/dhallj/tests/acceptance/AcceptanceSuites.scala

@@ -28,10 +28,7 @@ class TypeCheckingOtherSuite extends TypeCheckingSuite("type-inference/success")
   override def ignored = Set("CacheImports", "CacheImportsCanonicalize")
   override def slow = Set("prelude")
 }
-class TypeCheckingFailureUnitSuite extends TypeCheckingFailureSuite("type-inference/failure/unit") {
-  // The spec says we shouldn't have to worry about duplicate fields during type checking.
-  override def ignored = Set("RecordTypeDuplicateField")
-}
+class TypeCheckingFailureUnitSuite extends TypeCheckingFailureSuite("type-inference/failure/unit")
 
 class ParsingUnitSuite extends ParsingSuite("parser/success/unit") {
   override def ignored = Set("SomeXYZ")