From 51f3d868199b411a4b0a010c0a26585b5718e0fb Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sat, 21 Oct 2023 00:10:50 +0100
Subject: Support type checking field access on namespace

---
 .../shedlang/compiler/typechecker/TypeChecker.java | 30 ++++++++++++++++------
 .../compiler/typechecker/TypeCheckerContext.java   |  5 ++++
 .../errors/MissingNamespaceTypeInfoError.java      | 18 +++++++++++++
 .../shedlang/compiler/types/NamespaceTypeInfo.java |  6 +++++
 .../java/org/shedlang/compiler/types/Types.java    |  2 +-
 5 files changed, 52 insertions(+), 9 deletions(-)
 create mode 100644 src/main/java/org/shedlang/compiler/typechecker/errors/MissingNamespaceTypeInfoError.java

(limited to 'src/main/java')

diff --git a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
index 9157356d..30121611 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
@@ -430,14 +430,12 @@ public class TypeChecker {
         var typedReceiver = typedReceiverResult.value();
         context = typedReceiverResult.context();
 
-        if (!(typedReceiver.type() instanceof StructType receiverType)) {
-            throw new NoSuchFieldError(typedReceiver.type(), untyped.fieldName(), untyped.source());
-        }
-
-        var structTypeInfo = context.structTypeInfo(receiverType, untyped.source());
-
-        var fieldType = structTypeInfo.fieldType(untyped.fieldName())
-            .orElseThrow(() -> new NoSuchFieldError(receiverType, untyped.fieldName(), untyped.source()));
+        var fieldType = fieldType(
+            typedReceiver.type(),
+            untyped.fieldName(),
+            untyped.source(),
+            context
+        );
 
         return context.toResult(new TypedFieldAccessNode(
             typedReceiver,
@@ -447,6 +445,22 @@ public class TypeChecker {
         ));
     }
 
+    private static Type fieldType(Type receiverType, String fieldName, Source source, TypeCheckerContext context) {
+        if (receiverType instanceof StructType receiverTypeStruct) {
+            var structTypeInfo = context.structTypeInfo(receiverTypeStruct, source);
+
+            return structTypeInfo.fieldType(fieldName)
+                .orElseThrow(() -> new NoSuchFieldError(receiverTypeStruct, fieldName, source));
+        } else if (receiverType instanceof NamespaceType receiverTypeNamespace) {
+            var namespaceTypeInfo = context.namespaceTypeInfo(receiverTypeNamespace, source);
+
+            return namespaceTypeInfo.fieldType(fieldName)
+                .orElseThrow(() -> new NoSuchFieldError(receiverTypeNamespace, fieldName, source));
+        } else {
+            throw new NoSuchFieldError(receiverType, fieldName, source);
+        }
+    }
+
     private static TypeCheckSteps<TypedFunctionDefinitionNode> typeCheckStepsFunctionDefinition(
         UntypedFunctionDefinitionNode untyped
     ) {
diff --git a/src/main/java/org/shedlang/compiler/typechecker/TypeCheckerContext.java b/src/main/java/org/shedlang/compiler/typechecker/TypeCheckerContext.java
index 2fc19b80..8787be9a 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/TypeCheckerContext.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/TypeCheckerContext.java
@@ -357,6 +357,11 @@ public class TypeCheckerContext {
         );
     }
 
+    public NamespaceTypeInfo namespaceTypeInfo(NamespaceType type, Source source) {
+        return this.typeInfos.namespaceTypeInfo(type.namespaceName())
+            .orElseThrow(() -> new MissingNamespaceTypeInfoError(type, source));
+    }
+
     public TypeCheckerContext addStructTypeInfo(
         StructType structType,
         StructTypeInfo structTypeInfo
diff --git a/src/main/java/org/shedlang/compiler/typechecker/errors/MissingNamespaceTypeInfoError.java b/src/main/java/org/shedlang/compiler/typechecker/errors/MissingNamespaceTypeInfoError.java
new file mode 100644
index 00000000..922b08f9
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/typechecker/errors/MissingNamespaceTypeInfoError.java
@@ -0,0 +1,18 @@
+package org.shedlang.compiler.typechecker.errors;
+
+import org.shedlang.compiler.errors.InternalCompilerError;
+import org.shedlang.compiler.sources.Source;
+import org.shedlang.compiler.types.NamespaceType;
+
+public class MissingNamespaceTypeInfoError extends InternalCompilerError {
+    private final NamespaceType type;
+
+    public MissingNamespaceTypeInfoError(NamespaceType type, Source source) {
+        super("Missing type info for namespace " + type, source);
+        this.type = type;
+    }
+
+    public NamespaceType type() {
+        return type;
+    }
+}
diff --git a/src/main/java/org/shedlang/compiler/types/NamespaceTypeInfo.java b/src/main/java/org/shedlang/compiler/types/NamespaceTypeInfo.java
index d821f411..3e2b9ab0 100644
--- a/src/main/java/org/shedlang/compiler/types/NamespaceTypeInfo.java
+++ b/src/main/java/org/shedlang/compiler/types/NamespaceTypeInfo.java
@@ -2,6 +2,8 @@ package org.shedlang.compiler.types;
 
 import org.shedlang.compiler.util.POrderedMap;
 
+import java.util.Optional;
+
 public record NamespaceTypeInfo(FieldsInfo fields) {
     public static NamespaceTypeInfo fromFields(POrderedMap<String, Type> fields) {
         return new NamespaceTypeInfo(new FieldsInfo(fields));
@@ -11,6 +13,10 @@ public record NamespaceTypeInfo(FieldsInfo fields) {
         return fields.fieldCount();
     }
 
+    public <T> Optional<Type> fieldType(String fieldName) {
+        return fields.fieldType(fieldName);
+    }
+
     public int fieldIndex(String fieldName) {
         return fields.fieldIndex(fieldName);
     }
diff --git a/src/main/java/org/shedlang/compiler/types/Types.java b/src/main/java/org/shedlang/compiler/types/Types.java
index c349e27e..71c931b3 100644
--- a/src/main/java/org/shedlang/compiler/types/Types.java
+++ b/src/main/java/org/shedlang/compiler/types/Types.java
@@ -14,7 +14,7 @@ public class Types {
     public static final Type TOP = TopType.INSTANCE;
     public static final Type UNIT = UnitType.INSTANCE;
 
-    public static Type namespace(NamespaceName namespaceName) {
+    public static NamespaceType namespace(NamespaceName namespaceName) {
         return new NamespaceType(namespaceName);
     }
 
-- 
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