Throw error on unknown namespace field

4 files changed, 59 insertions, 6 deletions

diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java b/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java
index e9e7e74..78bdc97 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java
@@ -31,7 +31,13 @@ public class TypeChecker {
 
             var importedNamespaceFields = context.namespaceFields(importedNamespace);
             for (var importedName : untypedImport.importedNames()) {
-                namespaceContext.declare(importedName, importedNamespaceFields.get(importedName));
+                var fieldType = importedNamespaceFields.fieldType(importedName)
+                    .orElseThrow(() -> new UnknownNamespaceFieldError(
+                        importedName,
+                        importedNamespace,
+                        untypedImport.source()
+                    ));
+                namespaceContext.declare(importedName, fieldType);
             }
         }
 
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/UnknownNamespaceFieldError.java b/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/UnknownNamespaceFieldError.java
new file mode 100644
index 0000000..52f8b0a
--- /dev/null
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/UnknownNamespaceFieldError.java
@@ -0,0 +1,24 @@
+package org.zwobble.hobgoblin.compiler.typechecker;
+
+import org.zwobble.hobgoblin.compiler.errors.SourceError;
+import org.zwobble.hobgoblin.compiler.sources.Source;
+import org.zwobble.hobgoblin.compiler.types.NamespaceName;
+
+public class UnknownNamespaceFieldError extends SourceError {
+    private final String fieldName;
+    private final NamespaceName namespaceName;
+
+    public UnknownNamespaceFieldError(String fieldName, NamespaceName namespaceName, Source source) {
+        super("Unknown field " + fieldName + " on " + namespaceName, source);
+        this.fieldName = fieldName;
+        this.namespaceName = namespaceName;
+    }
+
+    public String fieldName() {
+        return fieldName;
+    }
+
+    public NamespaceName namespaceName() {
+        return namespaceName;
+    }
+}
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/types/Fields.java b/src/main/java/org/zwobble/hobgoblin/compiler/types/Fields.java
index 4fc364e..013a844 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/types/Fields.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/types/Fields.java
@@ -1,6 +1,7 @@
 package org.zwobble.hobgoblin.compiler.types;
 
 import java.util.List;
+import java.util.Optional;
 
 public class Fields {
     private final List<Field> fields;
@@ -9,12 +10,10 @@ public class Fields {
         this.fields = fields;
     }
 
-    public Type get(String name) {
+    public Optional<Type> fieldType(String name) {
         return fields.stream()
             .filter(field -> field.name().equals(name))
             .findFirst()
-            // TODO: better error handling
-            .orElseThrow()
-            .type();
+            .map(field -> field.type());
     }
 }
diff --git a/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerNamespaceTests.java b/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerNamespaceTests.java
index c4b31b8..3559578 100644
--- a/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerNamespaceTests.java
+++ b/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerNamespaceTests.java
@@ -9,6 +9,7 @@ import org.zwobble.hobgoblin.compiler.types.*;
 import java.util.List;
 import java.util.Optional;
 
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.zwobble.hobgoblin.compiler.types.TypeMatchers.isMetaType;
 import static org.zwobble.precisely.AssertThat.assertThat;
 import static org.zwobble.precisely.Matchers.*;
@@ -42,7 +43,7 @@ public class TypeCheckerNamespaceTests {
             ))
         ));
         assertThat(
-            context.namespaceFields(NamespaceName.of("a", "b")).get("X"),
+            context.namespaceFields(NamespaceName.of("a", "b")).fieldType("X").orElseThrow(),
             isMetaType(new StructType(NamespaceName.of("a", "b"), "X"))
         );
     }
@@ -97,4 +98,27 @@ public class TypeCheckerNamespaceTests {
             )
         );
     }
+
+    @Test
+    public void whenNamespaceHasNoSuchFieldThenErrorIsThrown() {
+        var untyped = UntypedNamespaceNode.arbitrary()
+            .withImports(List.of(
+                UntypedImportNode.arbitrary()
+                    .withAncestorDepth(Optional.empty())
+                    .withNamespaceName(NamespaceName.of("a"))
+                    .withImportedNames(List.of("A"))
+                    .build()
+            ))
+            .build();
+        var context = TypeCheckerContextArb.globalContext();
+        context.defineNamespace(NamespaceName.of("a"), List.of());
+
+        var error = assertThrows(
+            UnknownNamespaceFieldError.class,
+            () -> TypeChecker.typeCheckNamespace(untyped, context)
+        );
+
+        assertThat(error.fieldName(), equalTo("A"));
+        assertThat(error.namespaceName(), equalTo(NamespaceName.of("a")));
+    }
 }