Interfaces working?

example/src/main.nub

@@ -1,27 +1,32 @@
+extern func puts(fmt: cstring)
+
 interface Printable
 {
     func print()
 }
 
-struct Human : Printable {
+struct Human : Printable
+{
     name: cstring
 
-    func print_name()
-    {
-        puts(this^.name)
-    }
-
     func print()
     {
-        puts("example")
+        puts(this^.name)
     }
 }
 
 func main(args: []cstring): i64
 {
-    let human: Human = alloc Human {
+    let human = alloc Human {
         name = "oliver"
     }
+
     human.print()
+    print_printable(human)
     return 0
 }
+
+func print_printable(printable: Printable)
+{
+    printable.print()
+}

src/compiler/NubLang/Generation/QBE/QBEGenerator.Expression.cs

@@ -19,6 +19,7 @@ public partial class QBEGenerator
             BinaryExpressionNode binaryExpression => EmitBinaryExpression(binaryExpression),
             FuncCallNode funcCallExpression => EmitFuncCall(funcCallExpression),
             InterfaceFuncAccessNode interfaceFuncAccess => EmitInterfaceFuncAccess(interfaceFuncAccess),
+            InterfaceInitializerNode interfaceInitializer => EmitInterfaceInitializer(interfaceInitializer),
             ExternFuncIdentNode externFuncIdent => EmitExternFuncIdent(externFuncIdent),
             LocalFuncIdentNode localFuncIdent => EmitLocalFuncIdent(localFuncIdent),
             VariableIdentNode variableIdent => EmitVariableIdent(variableIdent),
@@ -329,15 +330,14 @@ public partial class QBEGenerator
         {
             destination = TmpName();
             var size = SizeOf(structInitializer.StructType);
-
-            if (structDef.InterfaceImplementations.Any())
-            {
-                size += 8;
-            }
-
             _writer.Indented($"{destination} =l alloc8 {size}");
         }
 
+        // if (structDef.InterfaceImplementations.Any())
+        // {
+        //     _writer.Indented($"storel {destination}, {StructVtableName(structDef.Name)}");
+        // }
+
         foreach (var field in structDef.Fields)
         {
             if (!structInitializer.Initializers.TryGetValue(field.Name, out var valueExpression))
@@ -424,15 +424,50 @@ public partial class QBEGenerator
     private Val EmitStructFuncAccess(StructFuncAccessNode structFuncAccess)
     {
         var target = EmitExpression(structFuncAccess.Target);
+        Debug.Assert(target.Kind == ValKind.Pointer);
+
         var structDef = _definitionTable.LookupStruct(structFuncAccess.StructType.Name);
         var func = StructFuncName(structDef.Name, structFuncAccess.Func);
 
-        return new Val(func, structFuncAccess.Type, ValKind.Direct, target);
+        return new Val(func, structFuncAccess.Type, ValKind.Direct, target.Name);
     }
 
     private Val EmitInterfaceFuncAccess(InterfaceFuncAccessNode interfaceFuncAccess)
     {
-        throw new NotImplementedException();
+        var target = EmitUnwrap(EmitExpression(interfaceFuncAccess.Target));
+
+        var interfaceDef = _definitionTable.LookupInterface(interfaceFuncAccess.InterfaceType.Name);
+        var functionIndex = interfaceDef.Functions.ToList().FindIndex(x => x.Name == interfaceFuncAccess.FuncName);
+        var offset = functionIndex * 8;
+
+        var vtable = TmpName();
+        _writer.Indented($"{vtable} =l loadl {target}");
+
+        var funcOffset = TmpName();
+        _writer.Indented($"{funcOffset} =l add {vtable}, {offset}");
+
+        var func = TmpName();
+        _writer.Indented($"{func} =l loadl {funcOffset}");
+
+        var data = TmpName();
+        _writer.Indented($"{data} =l add {target}, 8");
+
+        return new Val(func, interfaceFuncAccess.Type, ValKind.Direct, data);
+    }
+
+    private Val EmitInterfaceInitializer(InterfaceInitializerNode interfaceInitializer)
+    {
+        var implementation = EmitUnwrap(EmitExpression(interfaceInitializer.Implementation));
+
+        var result = TmpName();
+        _writer.Indented($"{result} =l alloc8 16");
+        _writer.Indented($"storel {StructVtableName(interfaceInitializer.StructType.Name)}, {result}");
+
+        var objectPointer = TmpName();
+        _writer.Indented($"{objectPointer} =l add {result}, 8");
+        _writer.Indented($"storel {implementation}, {objectPointer}");
+
+        return new Val(result, interfaceInitializer.InterfaceType, ValKind.Direct);
     }
 
     private Val EmitFuncCall(FuncCallNode funcCall)
@@ -444,8 +479,7 @@ public partial class QBEGenerator
 
         if (expression.ThisArg != null)
         {
-            Debug.Assert(expression.ThisArg.Kind == ValKind.Pointer);
+            parameterStrings.Add($"l {expression.ThisArg}");
-            parameterStrings.Add($"l {expression.ThisArg.Name}");
         }
 
         foreach (var parameter in funcCall.Parameters)

src/compiler/NubLang/Generation/QBE/QBEGenerator.cs

@@ -346,11 +346,6 @@ public partial class QBEGenerator
             return StructTypeName(structType.Name);
         }
 
-        if (complexType is InterfaceTypeNode interfaceType)
-        {
-            return InterfaceTypeName(interfaceType.Name);
-        }
-
         return "l";
     }
 
@@ -434,11 +429,6 @@ public partial class QBEGenerator
                 return StructTypeName(structType.Name);
             }
 
-            if (complexType is InterfaceTypeNode interfaceType)
-            {
-                return InterfaceTypeName(interfaceType.Name);
-            }
-
             return "l";
         }
     }
@@ -496,10 +486,10 @@ public partial class QBEGenerator
     {
         var offset = 0;
 
-        if (structType.InterfaceImplementations.Any())
+        // if (structType.InterfaceImplementations.Any())
-        {
+        // {
-            offset = 8;
+        //     offset = 8;
-        }
+        // }
 
         foreach (var field in structType.Fields)
         {
@@ -561,10 +551,10 @@ public partial class QBEGenerator
     {
         var offset = 0;
 
-        if (structDef.InterfaceImplementations.Any())
+        // if (structDef.InterfaceImplementations.Any())
-        {
+        // {
-            offset = 8;
+        //     offset = 8;
-        }
+        // }
 
         foreach (var field in structDef.Fields)
         {
@@ -619,11 +609,6 @@ public partial class QBEGenerator
         return $":{name}";
     }
 
-    private string InterfaceTypeName(string name)
-    {
-        return $":{name}";
-    }
-
     private string StructFuncName(string structName, string funcName)
     {
         return $"${structName}_{funcName}";
@@ -649,7 +634,7 @@ public class CStringLiteral(string value, string name)
     public string Name { get; } = name;
 }
 
-public record Val(string Name, TypeNode Type, ValKind Kind, Val? ThisArg = null);
+public record Val(string Name, TypeNode Type, ValKind Kind, string? ThisArg = null);
 
 public class Scope(Scope? parent = null)
 {

src/compiler/NubLang/TypeChecking/Node/ExpressionNode.cs

@@ -55,3 +55,5 @@ public record InterfaceFuncAccessNode(TypeNode Type, InterfaceTypeNode Interface
 public record StructInitializerNode(StructTypeNode StructType, Dictionary<string, ExpressionNode> Initializers) : ExpressionNode(StructType);
 
 public record DereferenceNode(TypeNode Type, ExpressionNode Expression) : ExpressionNode(Type);
+
+public record InterfaceInitializerNode(TypeNode Type, InterfaceTypeNode InterfaceType, StructTypeNode StructType, ExpressionNode Implementation) : ExpressionNode(Type);

src/compiler/NubLang/TypeChecking/TypeChecker.cs

@@ -204,22 +204,36 @@ public sealed class TypeChecker
     {
         TypeNode? type = null;
 
-        var assignment = Optional<ExpressionNode>.Empty();
-        if (statement.Assignment.HasValue)
-        {
-            var boundValue = CheckExpression(statement.Assignment.Value, type);
-            assignment = boundValue;
-            type = boundValue.Type;
-        }
-
         if (statement.ExplicitType.HasValue)
         {
             type = CheckType(statement.ExplicitType.Value);
         }
 
+        var assignment = Optional<ExpressionNode>.Empty();
+        if (statement.Assignment.HasValue)
+        {
+            var boundValue = CheckExpression(statement.Assignment.Value, type);
+            assignment = boundValue;
+
+            if (type != null)
+            {
+                if (boundValue.Type != type)
+                {
+                    throw new TypeCheckerException(Diagnostic.Error($"{boundValue.Type} is not assignable to {type}").Build());
+                }
+            }
+            else
+            {
                 if (type == null)
                 {
-            throw new NotImplementedException("Diagnostics not implemented");
+                    type = boundValue.Type;
+                }
+            }
+        }
+
+        if (type == null)
+        {
+            throw new TypeCheckerException(Diagnostic.Error($"Unknown type of variable {statement.Name}").Build());
         }
 
         Scope.Declare(new Variable(statement.Name, type));
@@ -234,7 +248,7 @@ public sealed class TypeChecker
 
     private ExpressionNode CheckExpression(ExpressionSyntax node, TypeNode? expectedType = null)
     {
-        return node switch
+        var result = node switch
         {
             AddressOfSyntax expression => CheckAddressOf(expression),
             ArrowFuncSyntax expression => CheckArrowFunc(expression, expectedType),
@@ -250,6 +264,27 @@ public sealed class TypeChecker
             UnaryExpressionSyntax expression => CheckUnaryExpression(expression),
             _ => throw new ArgumentOutOfRangeException(nameof(node))
         };
+
+        if (expectedType != null && result.Type != expectedType)
+        {
+            return CheckConversion(expectedType, result);
+        }
+
+        return result;
+    }
+
+    private ExpressionNode CheckConversion(TypeNode targetType, ExpressionNode expression)
+    {
+        // todo(nub): Add conversions for primitive types such as i32 -> i64 etc.
+        switch (expression.Type)
+        {
+            case StructTypeNode structType when targetType is InterfaceTypeNode interfaceType:
+            {
+                return new InterfaceInitializerNode(interfaceType, interfaceType, structType, expression);
+            }
+        }
+
+        throw new TypeCheckerException(Diagnostic.Error($"Cannot convert {expression.Type} to {targetType}").Build());
     }
 
     private AddressOfNode CheckAddressOf(AddressOfSyntax expression)
@@ -401,14 +436,14 @@ public sealed class TypeChecker
     {
         var boundExpression = CheckExpression(expression.Target);
 
-        if (boundExpression.Type is InterfaceTypeNode customType)
+        if (boundExpression.Type is InterfaceTypeNode interfaceType)
         {
-            var interfaces = _definitionTable.LookupInterface(customType.Name).ToArray();
+            var interfaces = _definitionTable.LookupInterface(interfaceType.Name).ToArray();
             if (interfaces.Length > 0)
             {
                 if (interfaces.Length > 1)
                 {
-                    throw new TypeCheckerException(Diagnostic.Error($"Interface {customType} has multiple definitions").Build());
+                    throw new TypeCheckerException(Diagnostic.Error($"Interface {interfaceType} has multiple definitions").Build());
                 }
 
                 var @interface = interfaces[0];
@@ -418,7 +453,7 @@ public sealed class TypeChecker
                 {
                     if (interfaceFuncs.Length > 1)
                     {
-                        throw new TypeCheckerException(Diagnostic.Error($"Interface {customType} has multiple functions with the name {expression.Member}").Build());
+                        throw new TypeCheckerException(Diagnostic.Error($"Interface {interfaceType} has multiple functions with the name {expression.Member}").Build());
                     }
 
                     var interfaceFunc = interfaceFuncs[0];
@@ -426,7 +461,7 @@ public sealed class TypeChecker
                     var returnType = CheckType(interfaceFunc.Signature.ReturnType);
                     var parameterTypes = interfaceFunc.Signature.Parameters.Select(p => CheckType(p.Type)).ToList();
                     var type = new FuncTypeNode(parameterTypes, returnType);
-                    return new InterfaceFuncAccessNode(type, customType, boundExpression, expression.Member);
+                    return new InterfaceFuncAccessNode(type, interfaceType, boundExpression, expression.Member);
                 }
             }
         }