...

example/src/main.nub

@@ -1,19 +1,30 @@
 // c
 extern func puts(text: cstring)
 
-struct Human {
+interface Printable
+{
+    func print()
+}
+
+struct Human : Printable
+{
     name: cstring
     age: u32
+
+    func print()
+    {
+        puts(this.name)
+    }
 }
 
 func main(args: []cstring): i64
 {
-    let x: Human = struct {
+    let x: Printable = struct Human {
         name = "Oliver"
         age = 23
     } 
 
-    puts(x.name)
+    x.print()
 
     return 0
 }

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

@@ -136,7 +136,7 @@ public class QBEGenerator
         _writer.Indented($"{store} {value}, {destination}");
     }
 
-    private Val EmitLoad(TypeNode type, string from)
+    private string EmitLoad(TypeNode type, string from)
     {
         string load;
 
@@ -164,7 +164,7 @@ public class QBEGenerator
 
         _writer.Indented($"{into} {QBEAssign(type)} {load} {from}");
 
-        return new Val(into, type, ValKind.Direct);
+        return into;
     }
 
     private void EmitMemcpy(string source, string destination, string length)
@@ -203,7 +203,7 @@ public class QBEGenerator
         {
             case ArrayInitializerNode arrayInitializer:
             {
-                EmitStore(source.Type, EmitUnwrap(EmitArrayInitializer(arrayInitializer)), destinationPointer);
+                EmitStore(source.Type, EmitArrayInitializer(arrayInitializer), destinationPointer);
                 return true;
             }
             case StructInitializerNode structInitializer:
@@ -218,7 +218,7 @@ public class QBEGenerator
             }
             case LiteralNode { Kind: LiteralKind.String } literal:
             {
-                EmitStore(source.Type, EmitUnwrap(EmitLiteral(literal)), destinationPointer);
+                EmitStore(source.Type, EmitLiteral(literal), destinationPointer);
                 return true;
             }
         }
@@ -368,7 +368,7 @@ public class QBEGenerator
 
         foreach (var parameter in funcDef.Signature.Parameters)
         {
-            scope.Declare(parameter.Name, new Val("%" + parameter.Name, parameter.Type, ValKind.Direct));
+            scope.Declare(parameter.Name, new Val("%" + parameter.Name, parameter.Type, false));
         }
 
         EmitBlock(funcDef.Body, scope);
@@ -410,10 +410,10 @@ public class QBEGenerator
 
             var scope = new Scope();
 
-            scope.Declare("this", new Val("%this", structDef.Type, ValKind.Direct));
+            scope.Declare("this", new Val("%this", structDef.Type, false));
             foreach (var parameter in function.Signature.Parameters)
             {
-                scope.Declare(parameter.Name, new Val("%" + parameter.Name, parameter.Type, ValKind.Direct));
+                scope.Declare(parameter.Name, new Val("%" + parameter.Name, parameter.Type, false));
             }
 
             EmitBlock(function.Body, scope);
@@ -531,12 +531,12 @@ public class QBEGenerator
 
     private void EmitAssignment(AssignmentNode assignment)
     {
-        var destination = EmitExpression(assignment.Target);
+        if (!assignment.Target.IsLValue)
-        if (destination.Kind != ValKind.Pointer)
         {
-            throw new UnreachableException("Destination of assignment must be a pointer. This should be caught in the type checker");
+            throw new UnreachableException("Destination of assignment must be an lvalue. This should have been caught in the type checker");
         }
 
+        var destination = EmitExpression(assignment.Target);
         EmitCopyIntoOrInitialize(assignment.Value, destination.Name);
     }
 
@@ -600,7 +600,7 @@ public class QBEGenerator
             EmitStore(variableDeclaration.Assignment.Value.Type, value, name);
         }
 
-        Scope.Declare(variableDeclaration.Name, new Val(name, variableDeclaration.Type, ValKind.Pointer));
+        Scope.Declare(variableDeclaration.Name, new Val(name, variableDeclaration.Type, true));
     }
 
     private void EmitWhile(WhileNode whileStatement)
@@ -626,7 +626,7 @@ public class QBEGenerator
 
     private Val EmitExpression(ExpressionNode expression)
     {
-        return expression switch
+        var value = expression switch
         {
             ArrayInitializerNode arrayInitializer => EmitArrayInitializer(arrayInitializer),
             StructInitializerNode structInitializer => EmitStructInitializer(structInitializer),
@@ -646,9 +646,11 @@ public class QBEGenerator
             ArrayIndexAccessNode arrayIndex => EmitArrayIndexAccess(arrayIndex),
             _ => throw new ArgumentOutOfRangeException(nameof(expression))
         };
+
+        return new Val(value, expression.Type, expression.IsLValue);
     }
 
-    private Val EmitArrayIndexAccess(ArrayIndexAccessNode arrayIndexAccess)
+    private string EmitArrayIndexAccess(ArrayIndexAccessNode arrayIndexAccess)
     {
         var array = EmitUnwrap(EmitExpression(arrayIndexAccess.Target));
         var index = EmitUnwrap(EmitExpression(arrayIndexAccess.Index));
@@ -661,7 +663,7 @@ public class QBEGenerator
         _writer.Indented($"{pointer} =l mul {index}, {SizeOf(elementType)}");
         _writer.Indented($"{pointer} =l add {pointer}, 8");
         _writer.Indented($"{pointer} =l add {array}, {pointer}");
-        return new Val(pointer, arrayIndexAccess.Type, ValKind.Pointer);
+        return pointer;
     }
 
     private void EmitArraysCheck(string array, string index)
@@ -688,7 +690,7 @@ public class QBEGenerator
         _writer.Indented(notOobLabel);
     }
 
-    private Val EmitArrayInitializer(ArrayInitializerNode arrayInitializer)
+    private string EmitArrayInitializer(ArrayInitializerNode arrayInitializer)
     {
         var capacity = EmitUnwrap(EmitExpression(arrayInitializer.Capacity));
         var elementSize = SizeOf(arrayInitializer.ElementType);
@@ -706,26 +708,26 @@ public class QBEGenerator
         _writer.Indented($"{dataPointer} =l add {arrayPointer}, 8");
         _writer.Indented($"call $nub_memset(l {dataPointer}, w 0, l {capacityInBytes})");
 
-        return new Val(arrayPointer, arrayInitializer.Type, ValKind.Direct);
+        return arrayPointer;
     }
 
-    private Val EmitDereference(DereferenceNode dereference)
+    private string EmitDereference(DereferenceNode dereference)
     {
         return EmitLoad(dereference.Type, EmitUnwrap(EmitExpression(dereference.Expression)));
     }
 
-    private Val EmitAddressOf(AddressOfNode addressOf)
+    private string EmitAddressOf(AddressOfNode addressOf)
     {
         var value = EmitExpression(addressOf.Expression);
-        if (value.Kind != ValKind.Pointer)
+        if (!value.IsLValue)
         {
-            throw new UnreachableException("Tried to take address of non-pointer type. This should have been caught in the type checker");
+            throw new UnreachableException("Tried to take address of rvalue. This should have been caught in the type checker");
         }
 
-        return new Val(value.Name, addressOf.Type, ValKind.Direct);
+        return value.Name;
     }
 
-    private Val EmitBinaryExpression(BinaryExpressionNode binaryExpression)
+    private string EmitBinaryExpression(BinaryExpressionNode binaryExpression)
     {
         var left = EmitUnwrap(EmitExpression(binaryExpression.Left));
         var right = EmitUnwrap(EmitExpression(binaryExpression.Right));
@@ -735,7 +737,7 @@ public class QBEGenerator
         var instruction = EmitBinaryInstructionFor(binaryExpression.Operator, binaryExpression.Left.Type, left, right);
 
         _writer.Indented($"{outputName} {QBEAssign(binaryExpression.Left.Type)} {instruction} {left}, {right}");
-        return new Val(outputName, binaryExpression.Type, ValKind.Direct);
+        return outputName;
     }
 
     private string EmitBinaryInstructionFor(BinaryOperator op, TypeNode type, string left, string right)
@@ -832,24 +834,24 @@ public class QBEGenerator
         };
     }
 
-    private Val EmitExternFuncIdent(ExternFuncIdentNode externFuncIdent)
+    private string EmitExternFuncIdent(ExternFuncIdentNode externFuncIdent)
     {
         var func = _definitionTable.LookupExternFunc(externFuncIdent.Name);
-        return new Val(ExternFuncName(func), externFuncIdent.Type, ValKind.Direct);
+        return ExternFuncName(func);
     }
 
-    private Val EmitLocalFuncIdent(LocalFuncIdentNode localFuncIdent)
+    private string EmitLocalFuncIdent(LocalFuncIdentNode localFuncIdent)
     {
         var func = _definitionTable.LookupLocalFunc(localFuncIdent.Name);
-        return new Val(LocalFuncName(func), localFuncIdent.Type, ValKind.Direct);
+        return LocalFuncName(func);
     }
 
-    private Val EmitVariableIdent(VariableIdentNode variableIdent)
+    private string EmitVariableIdent(VariableIdentNode variableIdent)
     {
-        return Scope.Lookup(variableIdent.Name);
+        return variableIdent.Name;
     }
 
-    private Val EmitLiteral(LiteralNode literal)
+    private string EmitLiteral(LiteralNode literal)
     {
         switch (literal.Kind)
         {
@@ -859,19 +861,19 @@ public class QBEGenerator
                 {
                     var value = float.Parse(literal.Value, CultureInfo.InvariantCulture);
                     var bits = BitConverter.SingleToInt32Bits(value);
-                    return new Val(bits.ToString(), literal.Type, ValKind.Direct);
+                    return bits.ToString();
                 }
 
                 if (literal.Type is FloatTypeNode { Width: 64 })
                 {
                     var value = double.Parse(literal.Value, CultureInfo.InvariantCulture);
                     var bits = BitConverter.DoubleToInt64Bits(value);
-                    return new Val(bits.ToString(), literal.Type, ValKind.Direct);
+                    return bits.ToString();
                 }
 
                 if (literal.Type is IntTypeNode)
                 {
-                    return new Val(literal.Value, literal.Type, ValKind.Direct);
+                    return literal.Value;
                 }
 
                 break;
@@ -880,21 +882,21 @@ public class QBEGenerator
             {
                 if (literal.Type is IntTypeNode)
                 {
-                    return new Val(literal.Value.Split(".").First(), literal.Type, ValKind.Direct);
+                    return literal.Value.Split(".").First();
                 }
 
                 if (literal.Type is FloatTypeNode { Width: 32 })
                 {
                     var value = float.Parse(literal.Value, CultureInfo.InvariantCulture);
                     var bits = BitConverter.SingleToInt32Bits(value);
-                    return new Val(bits.ToString(), literal.Type, ValKind.Direct);
+                    return bits.ToString();
                 }
 
                 if (literal.Type is FloatTypeNode { Width: 64 })
                 {
                     var value = double.Parse(literal.Value, CultureInfo.InvariantCulture);
                     var bits = BitConverter.DoubleToInt64Bits(value);
-                    return new Val(bits.ToString(), literal.Type, ValKind.Direct);
+                    return bits.ToString();
                 }
 
                 break;
@@ -905,14 +907,14 @@ public class QBEGenerator
                 {
                     var stringLiteral = new StringLiteral(literal.Value, StringName());
                     _stringLiterals.Add(stringLiteral);
-                    return new Val(stringLiteral.Name, literal.Type, ValKind.Direct);
+                    return stringLiteral.Name;
                 }
 
                 if (literal.Type is CStringTypeNode)
                 {
                     var cStringLiteral = new CStringLiteral(literal.Value, CStringName());
                     _cStringLiterals.Add(cStringLiteral);
-                    return new Val(cStringLiteral.Name, literal.Type, ValKind.Direct);
+                    return cStringLiteral.Name;
                 }
 
                 break;
@@ -921,7 +923,7 @@ public class QBEGenerator
             {
                 if (literal.Type is BoolTypeNode)
                 {
-                    return new Val(bool.Parse(literal.Value) ? "1" : "0", literal.Type, ValKind.Direct);
+                    return bool.Parse(literal.Value) ? "1" : "0";
                 }
 
                 break;
@@ -931,7 +933,7 @@ public class QBEGenerator
         throw new NotSupportedException($"Cannot create literal of kind '{literal.Kind}' for type {literal.Type}");
     }
 
-    private Val EmitStructInitializer(StructInitializerNode structInitializer, string? destination = null)
+    private string EmitStructInitializer(StructInitializerNode structInitializer, string? destination = null)
     {
         var structDef = _definitionTable.LookupStruct(structInitializer.StructType.Name);
 
@@ -959,10 +961,10 @@ public class QBEGenerator
             EmitCopyIntoOrInitialize(valueExpression, offset);
         }
 
-        return new Val(destination, structInitializer.StructType, ValKind.Direct);
+        return destination;
     }
 
-    private Val EmitUnaryExpression(UnaryExpressionNode unaryExpression)
+    private string EmitUnaryExpression(UnaryExpressionNode unaryExpression)
     {
         var operand = EmitUnwrap(EmitExpression(unaryExpression.Operand));
         var outputName = TmpName();
@@ -975,16 +977,16 @@ public class QBEGenerator
                 {
                     case IntTypeNode { Signed: true, Width: 64 }:
                         _writer.Indented($"{outputName} =l neg {operand}");
-                        return new Val(outputName, unaryExpression.Type, ValKind.Direct);
+                        return outputName;
                     case IntTypeNode { Signed: true, Width: 8 or 16 or 32 }:
                         _writer.Indented($"{outputName} =w neg {operand}");
-                        return new Val(outputName, unaryExpression.Type, ValKind.Direct);
+                        return outputName;
                     case FloatTypeNode { Width: 64 }:
                         _writer.Indented($"{outputName} =d neg {operand}");
-                        return new Val(outputName, unaryExpression.Type, ValKind.Direct);
+                        return outputName;
                     case FloatTypeNode { Width: 32 }:
                         _writer.Indented($"{outputName} =s neg {operand}");
-                        return new Val(outputName, unaryExpression.Type, ValKind.Direct);
+                        return outputName;
                 }
 
                 break;
@@ -995,7 +997,7 @@ public class QBEGenerator
                 {
                     case BoolTypeNode:
                         _writer.Indented($"{outputName} =w xor {operand}, 1");
-                        return new Val(outputName, unaryExpression.Type, ValKind.Direct);
+                        return outputName;
                 }
 
                 break;
@@ -1009,7 +1011,7 @@ public class QBEGenerator
         throw new NotSupportedException($"Unary operator {unaryExpression.Operator} for type {unaryExpression.Operand.Type} not supported");
     }
 
-    private Val EmitStructFieldAccess(StructFieldAccessNode structFieldAccess)
+    private string EmitStructFieldAccess(StructFieldAccessNode structFieldAccess)
     {
         var target = EmitUnwrap(EmitExpression(structFieldAccess.Target));
 
@@ -1019,16 +1021,10 @@ public class QBEGenerator
         var output = TmpName();
         _writer.Indented($"{output} =l add {target}, {offset}");
 
-        // If the accessed member is an inline struct, it will not be a pointer
+        return output;
-        if (structFieldAccess.Type is StructTypeNode)
-        {
-            return new Val(output, structFieldAccess.Type, ValKind.Direct);
-        }
-
-        return new Val(output, structFieldAccess.Type, ValKind.Pointer);
     }
 
-    private Val EmitStructFuncCall(StructFuncCallNode structFuncCall)
+    private string EmitStructFuncCall(StructFuncCallNode structFuncCall)
     {
         var structDef = _definitionTable.LookupStruct(structFuncCall.StructType.Name);
         var func = StructFuncName(structDef.Name, structFuncCall.Name);
@@ -1046,17 +1042,17 @@ public class QBEGenerator
         if (structFuncCall.Type is VoidTypeNode)
         {
             _writer.Indented($"call {func}({string.Join(", ", parameterStrings)})");
-            return new Val(string.Empty, structFuncCall.Type, ValKind.Direct);
+            return string.Empty;
         }
         else
         {
             var outputName = TmpName();
             _writer.Indented($"{outputName} {QBEAssign(structFuncCall.Type)} call {func}({string.Join(", ", parameterStrings)})");
-            return new Val(outputName, structFuncCall.Type, ValKind.Direct);
+            return outputName;
         }
     }
 
-    private Val EmitInterfaceFuncCall(InterfaceFuncCallNode interfaceFuncCall)
+    private string EmitInterfaceFuncCall(InterfaceFuncCallNode interfaceFuncCall)
     {
         var target = EmitUnwrap(EmitExpression(interfaceFuncCall.InterfaceExpression));
 
@@ -1087,17 +1083,17 @@ public class QBEGenerator
         if (interfaceFuncCall.Type is VoidTypeNode)
         {
             _writer.Indented($"call {func}({string.Join(", ", parameterStrings)})");
-            return new Val(string.Empty, interfaceFuncCall.Type, ValKind.Direct);
+            return string.Empty;
         }
         else
         {
             var outputName = TmpName();
             _writer.Indented($"{outputName} {QBEAssign(interfaceFuncCall.Type)} call {func}({string.Join(", ", parameterStrings)})");
-            return new Val(outputName, interfaceFuncCall.Type, ValKind.Direct);
+            return outputName;
         }
     }
 
-    private Val EmitInterfaceInitializer(InterfaceInitializerNode interfaceInitializer, string? destination = null)
+    private string EmitInterfaceInitializer(InterfaceInitializerNode interfaceInitializer, string? destination = null)
     {
         var implementation = EmitUnwrap(EmitExpression(interfaceInitializer.Implementation));
 
@@ -1126,10 +1122,10 @@ public class QBEGenerator
         _writer.Indented($"{objectPointer} =l add {destination}, 8");
         _writer.Indented($"storel {implementation}, {objectPointer}");
 
-        return new Val(destination, interfaceInitializer.InterfaceType, ValKind.Direct);
+        return destination;
     }
 
-    private Val EmitFuncCall(FuncCallNode funcCall)
+    private string EmitFuncCall(FuncCallNode funcCall)
     {
         var expression = EmitExpression(funcCall.Expression);
 
@@ -1145,24 +1141,19 @@ public class QBEGenerator
         if (funcCall.Type is VoidTypeNode)
         {
             _writer.Indented($"call {funcPointer}({string.Join(", ", parameterStrings)})");
-            return new Val(string.Empty, funcCall.Type, ValKind.Direct);
+            return string.Empty;
         }
         else
         {
             var outputName = TmpName();
             _writer.Indented($"{outputName} {QBEAssign(funcCall.Type)} call {funcPointer}({string.Join(", ", parameterStrings)})");
-            return new Val(outputName, funcCall.Type, ValKind.Direct);
+            return outputName;
         }
     }
 
     private string EmitUnwrap(Val val)
     {
-        return val.Kind switch
+        return val.Name;
-        {
-            ValKind.Direct => val.Name,
-            ValKind.Pointer => EmitLoad(val.Type, val.Name).Name,
-            _ => throw new ArgumentOutOfRangeException()
-        };
     }
 
     private static int SizeOf(TypeNode type)
@@ -1329,7 +1320,7 @@ public class CStringLiteral(string value, string name)
     public string Name { get; } = name;
 }
 
-public record Val(string Name, TypeNode Type, ValKind Kind);
+public record Val(string Name, TypeNode Type, bool IsLValue);
 
 public class Scope(Scope? parent = null)
 {
@@ -1355,10 +1346,4 @@ public class Scope(Scope? parent = null)
     {
         return new Scope(this);
     }
-}
-
-public enum ValKind
-{
-    Pointer,
-    Direct,
 }

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

@@ -22,36 +22,36 @@ public enum BinaryOperator
     Divide
 }
 
-public abstract record ExpressionNode(TypeNode Type) : Node;
+public abstract record ExpressionNode(TypeNode Type, bool IsLValue) : Node;
 
-public record BinaryExpressionNode(TypeNode Type, ExpressionNode Left, BinaryOperator Operator, ExpressionNode Right) : ExpressionNode(Type);
+public record BinaryExpressionNode(TypeNode Type, ExpressionNode Left, BinaryOperator Operator, ExpressionNode Right) : ExpressionNode(Type, false);
 
-public record UnaryExpressionNode(TypeNode Type, UnaryOperator Operator, ExpressionNode Operand) : ExpressionNode(Type);
+public record UnaryExpressionNode(TypeNode Type, UnaryOperator Operator, ExpressionNode Operand) : ExpressionNode(Type, false);
 
-public record FuncCallNode(TypeNode Type, ExpressionNode Expression, IReadOnlyList<ExpressionNode> Parameters) : ExpressionNode(Type);
+public record FuncCallNode(TypeNode Type, ExpressionNode Expression, IReadOnlyList<ExpressionNode> Parameters) : ExpressionNode(Type, false);
 
-public record StructFuncCallNode(TypeNode Type, string Name, StructTypeNode StructType, ExpressionNode StructExpression, IReadOnlyList<ExpressionNode> Parameters) : ExpressionNode(Type);
+public record StructFuncCallNode(TypeNode Type, string Name, StructTypeNode StructType, ExpressionNode StructExpression, IReadOnlyList<ExpressionNode> Parameters) : ExpressionNode(Type, false);
 
-public record InterfaceFuncCallNode(TypeNode Type, string Name, InterfaceTypeNode InterfaceType, ExpressionNode InterfaceExpression, IReadOnlyList<ExpressionNode> Parameters) : ExpressionNode(Type);
+public record InterfaceFuncCallNode(TypeNode Type, string Name, InterfaceTypeNode InterfaceType, ExpressionNode InterfaceExpression, IReadOnlyList<ExpressionNode> Parameters) : ExpressionNode(Type, false);
 
-public record VariableIdentNode(TypeNode Type, string Name) : ExpressionNode(Type);
+public record VariableIdentNode(TypeNode Type, string Name) : ExpressionNode(Type, true);
 
-public record LocalFuncIdentNode(TypeNode Type, string Name) : ExpressionNode(Type);
+public record LocalFuncIdentNode(TypeNode Type, string Name) : ExpressionNode(Type, false);
 
-public record ExternFuncIdentNode(TypeNode Type, string Name) : ExpressionNode(Type);
+public record ExternFuncIdentNode(TypeNode Type, string Name) : ExpressionNode(Type, false);
 
-public record ArrayInitializerNode(TypeNode Type, ExpressionNode Capacity, TypeNode ElementType) : ExpressionNode(Type);
+public record ArrayInitializerNode(TypeNode Type, ExpressionNode Capacity, TypeNode ElementType) : ExpressionNode(Type, true);
 
-public record ArrayIndexAccessNode(TypeNode Type, ExpressionNode Target, ExpressionNode Index) : ExpressionNode(Type);
+public record ArrayIndexAccessNode(TypeNode Type, ExpressionNode Target, ExpressionNode Index) : ExpressionNode(Type, true);
 
-public record AddressOfNode(TypeNode Type, ExpressionNode Expression) : ExpressionNode(Type);
+public record AddressOfNode(TypeNode Type, ExpressionNode Expression) : ExpressionNode(Type, false);
 
-public record LiteralNode(TypeNode Type, string Value, LiteralKind Kind) : ExpressionNode(Type);
+public record LiteralNode(TypeNode Type, string Value, LiteralKind Kind) : ExpressionNode(Type, false);
 
-public record StructFieldAccessNode(TypeNode Type, StructTypeNode StructType, ExpressionNode Target, string Field) : ExpressionNode(Type);
+public record StructFieldAccessNode(TypeNode Type, StructTypeNode StructType, ExpressionNode Target, string Field) : ExpressionNode(Type, true);
 
-public record StructInitializerNode(StructTypeNode StructType, Dictionary<string, ExpressionNode> Initializers) : ExpressionNode(StructType);
+public record StructInitializerNode(StructTypeNode StructType, Dictionary<string, ExpressionNode> Initializers) : ExpressionNode(StructType, true);
 
-public record DereferenceNode(TypeNode Type, ExpressionNode Expression) : ExpressionNode(Type);
+public record DereferenceNode(TypeNode Type, ExpressionNode Expression) : ExpressionNode(Type, false);
 
-public record InterfaceInitializerNode(TypeNode Type, InterfaceTypeNode InterfaceType, StructTypeNode StructType, ExpressionNode Implementation) : ExpressionNode(Type);
+public record InterfaceInitializerNode(TypeNode Type, InterfaceTypeNode InterfaceType, StructTypeNode StructType, ExpressionNode Implementation) : ExpressionNode(Type, true);