From 032cdc6462ad575f62b349152f31e87b187e974d Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sat, 25 Apr 2026 10:33:55 +0100
Subject: Generate struct type for struct definition

---
 .../compiler/typechecker/TypeChecker.java          | 34 ++++++++++++++++----
 .../compiler/typechecker/TypeCheckerContext.java   | 19 +++++++++--
 .../typechecker/TypeCheckerContextArb.java         |  2 +-
 .../TypeCheckerStructDefinitionTests.java          | 37 ++++++++++++++++++++++
 4 files changed, 83 insertions(+), 9 deletions(-)
 create mode 100644 src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerStructDefinitionTests.java

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 cfce407..0a301c6 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java
@@ -1,11 +1,8 @@
 package org.zwobble.hobgoblin.compiler.typechecker;
 
-import org.zwobble.hobgoblin.compiler.ast.typed.TypedNamespaceNode;
-import org.zwobble.hobgoblin.compiler.ast.typed.TypedTypeLevelExpressionNode;
-import org.zwobble.hobgoblin.compiler.ast.typed.TypedTypeLevelReferenceNode;
-import org.zwobble.hobgoblin.compiler.ast.untyped.UntypedNamespaceNode;
-import org.zwobble.hobgoblin.compiler.ast.untyped.UntypedTypeLevelExpressionNode;
-import org.zwobble.hobgoblin.compiler.ast.untyped.UntypedTypeLevelReferenceNode;
+import org.zwobble.hobgoblin.compiler.ast.typed.*;
+import org.zwobble.hobgoblin.compiler.ast.untyped.*;
+import org.zwobble.hobgoblin.compiler.types.StructType;
 import org.zwobble.hobgoblin.compiler.types.TypeLevelValue;
 import org.zwobble.hobgoblin.compiler.types.TypeLevelValueType;
 import org.zwobble.hobgoblin.compiler.types.TypeSet;
@@ -27,6 +24,31 @@ public class TypeChecker {
         );
     }
 
+    static TypedNamespaceStatementNode typeCheckNamespaceStatement(
+        UntypedNamespaceStatementNode untyped,
+        TypeCheckerContext context
+    ) {
+        return switch (untyped) {
+            case UntypedStructDefinitionNode untypedStructDefinition ->
+                typeCheckStructDefinition(untypedStructDefinition, context);
+        };
+    }
+
+    private static TypedStructDefinitionNode typeCheckStructDefinition(
+        UntypedStructDefinitionNode untyped,
+        TypeCheckerContext context
+    ) {
+        // TODO: better error when not in namespace
+        var namespaceName = context.namespaceName().orElseThrow();
+        var structType = new StructType(namespaceName, untyped.name());
+
+        return new TypedStructDefinitionNode(
+            structType,
+            List.of(),
+            untyped.source()
+        );
+    }
+
     static TypedTypeLevelExpressionNode<? extends TypeLevelValue> typeCheckTypeLevelExpression(
         UntypedTypeLevelExpressionNode untyped,
         TypeCheckerContext context
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerContext.java b/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerContext.java
index b80246a..e1109f9 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerContext.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerContext.java
@@ -1,5 +1,6 @@
 package org.zwobble.hobgoblin.compiler.typechecker;
 
+import org.zwobble.hobgoblin.compiler.types.NamespaceName;
 import org.zwobble.hobgoblin.compiler.types.Type;
 
 import java.util.HashMap;
@@ -7,10 +8,20 @@ import java.util.Map;
 import java.util.Optional;
 
 public class TypeCheckerContext {
-    private final Map<String, Variable> variables = new HashMap<>();
+    private Optional<NamespaceName> namespaceName;
+    private final Map<String, Variable> variables;
+
+    private TypeCheckerContext(Optional<NamespaceName> namespaceName, Map<String, Variable> variables) {
+        this.namespaceName = namespaceName;
+        this.variables = variables;
+    }
 
     public static TypeCheckerContext initial() {
-        return new TypeCheckerContext();
+        return new TypeCheckerContext(Optional.empty(), new HashMap<>());
+    }
+
+    public Optional<NamespaceName> namespaceName() {
+        return this.namespaceName;
     }
 
     public void declare(String name) {
@@ -26,4 +37,8 @@ public class TypeCheckerContext {
     public Optional<Variable> lookup(String name) {
         return Optional.ofNullable(this.variables.get(name));
     }
+
+    public void enterNamespace(NamespaceName namespaceName) {
+        this.namespaceName = Optional.of(namespaceName);
+    }
 }
diff --git a/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerContextArb.java b/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerContextArb.java
index 98d8064..b917ba4 100644
--- a/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerContextArb.java
+++ b/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerContextArb.java
@@ -5,6 +5,6 @@ public class TypeCheckerContextArb {
     }
 
     public static TypeCheckerContext context() {
-        return new TypeCheckerContext();
+        return TypeCheckerContext.initial();
     }
 }
diff --git a/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerStructDefinitionTests.java b/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerStructDefinitionTests.java
new file mode 100644
index 0000000..86f78ae
--- /dev/null
+++ b/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerStructDefinitionTests.java
@@ -0,0 +1,37 @@
+package org.zwobble.hobgoblin.compiler.typechecker;
+
+import org.junit.jupiter.api.Test;
+import org.zwobble.hobgoblin.compiler.ast.typed.TypedStructDefinitionNode;
+import org.zwobble.hobgoblin.compiler.ast.untyped.UntypedStructDefinitionNode;
+import org.zwobble.hobgoblin.compiler.sources.NullSource;
+import org.zwobble.hobgoblin.compiler.types.NamespaceName;
+import org.zwobble.hobgoblin.compiler.types.StructType;
+
+import java.util.List;
+
+import static org.zwobble.precisely.AssertThat.assertThat;
+import static org.zwobble.precisely.Matchers.*;
+
+public class TypeCheckerStructDefinitionTests {
+    @Test
+    public void structHasNamespaceFromContext() {
+        var untyped = new UntypedStructDefinitionNode(
+            "X",
+            List.of(),
+            NullSource.INSTANCE
+        );
+        var context = TypeCheckerContextArb.context();
+        context.enterNamespace(NamespaceName.of("a", "b"));
+
+        var typed = TypeChecker.typeCheckNamespaceStatement(untyped, context);
+
+        assertThat(typed, instanceOf(
+            TypedStructDefinitionNode.class,
+            has(
+                "type",
+                TypedStructDefinitionNode::type,
+                equalTo(new StructType(NamespaceName.of("a", "b"), "X"))
+            )
+        ));
+    }
+}
-- 
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