Improve code handling

backend_wat.go

@@ -4,7 +4,6 @@ import (
 	"errors"
 	"fmt"
 	"strconv"
-	"strings"
 	"unicode"
 )
 
@@ -50,37 +49,37 @@ func safeASCIIIdentifier(identifier string) string {
 	return ascii
 }
 
-func getTypeCast(primitive PrimitiveType) string {
+func getTypeCast(primitive PrimitiveType) Code {
 	switch primitive {
 	case Primitive_I8:
-		return "i32.extend8_s\n"
+		return ofInstruction("i32.extend8_s")
 	case Primitive_U8:
-		return "i32.const 255\ni32.and\n"
+		return ofInstruction("i32.const 255", "i32.and")
 	case Primitive_I16:
-		return "i32.extend16_s\n"
+		return ofInstruction("i32.extend16_s")
 	case Primitive_U16:
-		return "i32.const 65535\ni32.and\n"
+		return ofInstruction("i32.const 65535", "i32.and")
 	case Primitive_Bool:
-		return "i32.const 0\ni32.ne\n"
+		return ofInstruction("i32.const 0", "i32.ne")
 	}
 
-	return ""
+	return emptyCode()
 }
 
-func pushConstantNumberWAT(primitive PrimitiveType, value any) string {
+func pushConstantNumberWAT(primitive PrimitiveType, value any) Code {
 	switch primitive {
 	case Primitive_I8, Primitive_I16, Primitive_I32:
-		return "i32.const " + strconv.FormatInt(value.(int64), 10) + "\n"
+		return ofInstruction("i32.const " + strconv.FormatInt(value.(int64), 10))
 	case Primitive_U8, Primitive_U16, Primitive_U32:
-		return "i32.const " + strconv.FormatUint(value.(uint64), 10) + "\n"
+		return ofInstruction("i32.const " + strconv.FormatUint(value.(uint64), 10))
 	case Primitive_I64:
-		return "i64.const " + strconv.FormatInt(value.(int64), 10) + "\n"
+		return ofInstruction("i64.const " + strconv.FormatInt(value.(int64), 10))
 	case Primitive_U64:
-		return "i64.const " + strconv.FormatUint(value.(uint64), 10) + "\n"
+		return ofInstruction("i64.const " + strconv.FormatUint(value.(uint64), 10))
 	case Primitive_F32:
-		return "f32.const " + strconv.FormatFloat(value.(float64), 'f', -1, 32) + "\n"
+		return ofInstruction("f32.const " + strconv.FormatFloat(value.(float64), 'f', -1, 32))
 	case Primitive_F64:
-		return "f64.const " + strconv.FormatFloat(value.(float64), 'f', -1, 64) + "\n"
+		return ofInstruction("f64.const " + strconv.FormatFloat(value.(float64), 'f', -1, 64))
 	}
 
 	panic(fmt.Sprintf("invalid type passed to pushConstantNumberWAT(): %s", primitive))
@@ -143,38 +142,39 @@ func (c *Compiler) getTypeSizeBytes(t Type) int {
 	panic(fmt.Sprintf("unhandled type in getTypeSizeBytes(): %s", t))
 }
 
-func castPrimitiveWAT(from PrimitiveType, to PrimitiveType) (string, error) {
+func castPrimitiveWAT(from PrimitiveType, to PrimitiveType) (Code, error) {
 	if from == to {
-		return "", nil
+		return emptyCode(), nil
 	}
 
 	if from == Primitive_Bool || to == Primitive_Bool {
-		return "", errors.New("cannot upcast from or to bool")
+		return emptyCode(), errors.New("cannot upcast from or to bool")
 	}
 
 	fromFloat := isFloatingPoint(from)
 	toFloat := isFloatingPoint(to)
 	if fromFloat && toFloat {
 		if to == Primitive_F32 {
-			return "f32.demote_f64\n", nil
+			return ofInstruction("f32.demote_f64"), nil
 		} else {
-			return "f64.promote_f32\n", nil
+			return ofInstruction("f64.promote_f32"), nil
 		}
 	}
 
 	if toFloat {
-		suffix := ""
+		var suffix string
+
 		if isUnsignedInt(to) {
 			suffix = "u"
 		} else {
 			suffix = "s"
 		}
 
-		return getPrimitiveWATType(to) + ".convert_" + getPrimitiveWATType(from) + "_" + suffix + "\n", nil
+		return ofInstruction(getPrimitiveWATType(to) + ".convert_" + getPrimitiveWATType(from) + "_" + suffix), nil
 	}
 
 	if fromFloat {
-		suffix := ""
+		var suffix string
 
 		if isUnsignedInt(to) {
 			suffix = "u"
@@ -182,11 +182,11 @@ func castPrimitiveWAT(from PrimitiveType, to PrimitiveType) (string, error) {
 			suffix = "s"
 		}
 
-		return getPrimitiveWATType(to) + ".trunc_" + getPrimitiveWATType(from) + "_" + suffix + "\n", nil
+		return ofInstruction(getPrimitiveWATType(to) + ".trunc_" + getPrimitiveWATType(from) + "_" + suffix), nil
 	}
 
 	if getBits(from) == getBits(to) {
-		return "", nil
+		return emptyCode(), nil
 	}
 
 	if getPrimitiveWATType(from) == getPrimitiveWATType(to) {
@@ -194,36 +194,41 @@ func castPrimitiveWAT(from PrimitiveType, to PrimitiveType) (string, error) {
 			return getTypeCast(to), nil
 		}
 
-		return "", nil
+		return emptyCode(), nil
 	}
 
 	if getBits(from) < 64 && getBits(to) == 64 {
-		suffix := ""
+		var suffix string
+
 		if isUnsignedInt(from) {
 			suffix = "u"
 		} else {
 			suffix = "s"
 		}
 
-		return "i64.extend_i32_" + suffix + "\n", nil
+		return ofInstruction("i64.extend_i32_" + suffix), nil
 	}
 
-	return "i32.wrap_i64\n" + getTypeCast(to), nil
+	code := ofInstruction("i32.wrap_i64")
+	code.addAll(getTypeCast(to))
+	return code, nil
 }
 
-func (c *Compiler) compileAssignmentExpressionWAT(assignment AssignmentExpression) (string, error) {
+func (c *Compiler) compileAssignmentExpressionWAT(assignment AssignmentExpression) (Code, error) {
 	lhs := assignment.Lhs
 
 	exprWAT, err := c.compileExpressionWAT(assignment.Value)
 	if err != nil {
-		return "", err
+		return emptyCode(), err
 	}
 
 	switch lhs.Type {
 	case Expression_VariableReference:
 		ref := lhs.Value.(VariableReferenceExpression)
 		local := strconv.Itoa(getLocal(c.CurrentBlock, ref.Variable).Index)
-		return exprWAT + "local.tee $" + local + "\n", nil
+
+		exprWAT.add("local.tee $" + local)
+		return exprWAT, nil
 	case Expression_ArrayAccess:
 		array := lhs.Value.(ArrayAccessExpression)
 
@@ -238,63 +243,72 @@ func (c *Compiler) compileAssignmentExpressionWAT(assignment AssignmentExpressio
 
 		arrayWAT, err := c.compileExpressionWAT(array.Array)
 		if err != nil {
-			return "", err
+			return emptyCode(), err
 		}
 
-		arrayWAT += "local.set $" + strconv.Itoa(localArray.Index) + "\n"
+		arrayWAT.add("local.set $" + strconv.Itoa(localArray.Index))
 
 		indexWAT, err := c.compileExpressionWAT(array.Index)
 		if err != nil {
-			return "", err
+			return emptyCode(), err
 		}
 
 		if !c.Wasm64 {
 			cast, err := castPrimitiveWAT(Primitive_I64, Primitive_I32)
 			if err != nil {
-				return "", err
+				return emptyCode(), err
 			}
 
-			indexWAT += cast
+			indexWAT.addAll(cast)
 		}
 
-		indexWAT += "local.set $" + strconv.Itoa(localIndex.Index) + "\n"
+		indexWAT.add("local.set $" + strconv.Itoa(localIndex.Index))
 
-		wat := arrayWAT + indexWAT
+		wat := concat(arrayWAT, indexWAT)
 
 		if _, ok := c.CompileOptions[COMPILE_OPTION_NO_BOUNDS_CHECK]; !ok {
 			// Error if index < 0
-			wat += "block\n"
+			wat.add(
-			wat += "local.get $" + strconv.Itoa(localIndex.Index) + "\n"
+				"block",
-			wat += c.getAddressWATType() + ".const 0\n"
+				"local.get $"+strconv.Itoa(localIndex.Index),
-			wat += c.getAddressWATType() + ".ge_s\n"
+				c.getAddressWATType()+".const 0",
-			wat += "br_if 0\n"
+				c.getAddressWATType()+".ge_s",
-			wat += "call $__builtin_panic\n"
+				"br_if 0",
-			wat += "end\n"
+				"call $__builtin_panic",
+				"end",
+			)
 
 			// Error if index >= array length
-			wat += "block\n"
+			wat.add(
-			wat += "local.get $" + strconv.Itoa(localIndex.Index) + "\n"
+				"block",
-			wat += "local.get $" + strconv.Itoa(localArray.Index) + "\n"
+				"local.get $"+strconv.Itoa(localIndex.Index),
-			wat += "i32.load\n" // Load array length
+				"local.get $"+strconv.Itoa(localArray.Index),
-			wat += c.getAddressWATType() + ".lt_s\n"
+				"i32.load", // Load array length
-			wat += "br_if 0\n"
+				c.getAddressWATType()+".lt_s",
-			wat += "call $__builtin_panic\n"
+				"br_if 0",
-			wat += "end\n"
+				"call $__builtin_panic",
+				"end",
+			)
 		}
 
 		elementType := array.Array.ValueType.Value.(ArrayType).ElementType
-		wat += "local.get $" + strconv.Itoa(localIndex.Index) + "\n"
+		wat.add(
-		wat += c.getAddressWATType() + ".const " + strconv.Itoa(c.getTypeSizeBytes(elementType)) + "\n"
+			"local.get $"+strconv.Itoa(localIndex.Index),
-		wat += c.getAddressWATType() + ".mul\n"
+			c.getAddressWATType()+".const "+strconv.Itoa(c.getTypeSizeBytes(elementType)),
-		wat += "local.get $" + strconv.Itoa(localArray.Index) + "\n"
+			c.getAddressWATType()+".mul",
-		wat += c.getAddressWATType() + ".add\n"
+			"local.get $"+strconv.Itoa(localArray.Index),
-		wat += c.getAddressWATType() + ".const 4\n" // first 4 bytes = length
+			c.getAddressWATType()+".add",
-		wat += c.getAddressWATType() + ".add\n"
+			c.getAddressWATType()+".const 4", // first 4 bytes = length
+			c.getAddressWATType()+".add",
+		)
 
-		wat += exprWAT
+		wat.addAll(exprWAT)
-		wat += "local.tee $" + strconv.Itoa(localElement.Index) + "\n"
+
-		wat += c.getWATType(elementType) + ".store\n" // TODO: use load8/load16(_s/u) for smaller types
+		wat.add(
-		wat += "local.get $" + strconv.Itoa(localElement.Index) + "\n"
+			"local.tee $"+strconv.Itoa(localElement.Index),
+			c.getWATType(elementType)+".store", // TODO: use load8/load16(_s/u) for smaller types
+			"local.get $"+strconv.Itoa(localElement.Index),
+		)
 
 		return wat, nil
 	case Expression_RawMemoryReference:
@@ -309,20 +323,25 @@ func (c *Compiler) compileAssignmentExpressionWAT(assignment AssignmentExpressio
 
 		addrWAT, err := c.compileExpressionWAT(raw.Address)
 		if err != nil {
-			return "", err
+			return emptyCode(), err
 		}
 
 		// TODO: should leave a copy of the stored value on the stack
-		return addrWAT + exprWAT +
+		code := addrWAT.clone()
-			"local.tee $" + strconv.Itoa(local.Index) + "\n" +
+		code.addAll(exprWAT)
-			c.getWATType(raw.Type) + ".store\n" +
+		code.add(
-			"local.get $" + strconv.Itoa(local.Index) + "\n", nil
+			"local.tee $"+strconv.Itoa(local.Index),
+			c.getWATType(raw.Type)+".store",
+			"local.get $"+strconv.Itoa(local.Index),
+		)
+
+		return code, nil
 	}
 
 	panic("assignment expr not implemented")
 }
 
-func (c *Compiler) compileAssignmentUpdateExpressionWAT(lhs Expression, updateWAT string, evaluateToOldValue bool) (string, error) {
+func (c *Compiler) compileAssignmentUpdateExpressionWAT(lhs Expression, updateWAT Code, evaluateToOldValue bool) (Code, error) {
 	switch lhs.Type {
 	case Expression_VariableReference:
 		ref := lhs.Value.(VariableReferenceExpression)
@@ -330,25 +349,27 @@ func (c *Compiler) compileAssignmentUpdateExpressionWAT(lhs Expression, updateWA
 
 		exprWAT, err := c.compileExpressionWAT(lhs)
 		if err != nil {
-			return "", err
+			return emptyCode(), err
 		}
 
 		var tmpLocal Local
-		wat := exprWAT
+		wat := exprWAT.clone()
 		if evaluateToOldValue {
 			tmpLocal = Local{Name: "", Type: *lhs.ValueType, IsParameter: false, Index: len(c.CurrentFunction.Locals)}
 			c.CurrentFunction.Locals = append(c.CurrentFunction.Locals, tmpLocal)
 
-			wat += "local.tee $" + strconv.Itoa(tmpLocal.Index) + "\n"
+			wat.add("local.tee $" + strconv.Itoa(tmpLocal.Index))
 		}
 
-		wat += updateWAT
+		wat.addAll(updateWAT)
 
 		if evaluateToOldValue {
-			wat += "local.set $" + local + "\n"
+			wat.add(
-			wat += "local.get $" + strconv.Itoa(tmpLocal.Index) + "\n"
+				"local.set $"+local,
+				"local.get $"+strconv.Itoa(tmpLocal.Index),
+			)
 		} else {
-			wat += "local.tee $" + local + "\n"
+			wat.add("local.tee $" + local)
 		}
 
 		return wat, nil
@@ -369,29 +390,33 @@ func (c *Compiler) compileAssignmentUpdateExpressionWAT(lhs Expression, updateWA
 
 		addrWAT, err := c.compileExpressionWAT(raw.Address)
 		if err != nil {
-			return "", err
+			return emptyCode(), err
 		}
 
 		wat := addrWAT
 
 		// dup address
-		wat += "local.tee $" + strconv.Itoa(localAddress.Index) + "\n"
+		wat.add(
-		wat += "local.get $" + strconv.Itoa(localAddress.Index) + "\n"
+			"local.tee $"+strconv.Itoa(localAddress.Index),
+			"local.get $"+strconv.Itoa(localAddress.Index),
+		)
 
-		wat += c.getWATType(raw.Type) + ".load\n"
+		wat.add(c.getWATType(raw.Type) + ".load")
 
 		if evaluateToOldValue {
-			wat += "local.tee $" + strconv.Itoa(localValue.Index) + "\n"
+			wat.add("local.tee $" + strconv.Itoa(localValue.Index))
 		}
 
-		wat += updateWAT
+		wat.addAll(updateWAT)
 
 		if !evaluateToOldValue {
-			wat += "local.tee $" + strconv.Itoa(localValue.Index) + "\n"
+			wat.add("local.tee $" + strconv.Itoa(localValue.Index))
 		}
 
-		wat += c.getWATType(raw.Type) + ".store\n"
+		wat.add(
-		wat += "local.get $" + strconv.Itoa(localValue.Index) + "\n"
+			c.getWATType(raw.Type)+".store",
+			"local.get $"+strconv.Itoa(localValue.Index),
+		)
 
 		return wat, nil
 	}
@@ -399,7 +424,7 @@ func (c *Compiler) compileAssignmentUpdateExpressionWAT(lhs Expression, updateWA
 	panic("assignment expr not implemented")
 }
 
-func (c *Compiler) compileExpressionWAT(expr Expression) (string, error) {
+func (c *Compiler) compileExpressionWAT(expr Expression) (Code, error) {
 	var err error
 
 	switch expr.Type {
@@ -412,12 +437,13 @@ func (c *Compiler) compileExpressionWAT(expr Expression) (string, error) {
 
 		watRight, err := c.compileExpressionWAT(ass.Value)
 		if err != nil {
-			return "", err
+			return emptyCode(), err
 		}
 
 		updateOp := c.compileOperationWAT(ass.Operation, ass.Lhs.ValueType.Value.(PrimitiveType))
+		watRight.addAll(updateOp)
 
-		return c.compileAssignmentUpdateExpressionWAT(ass.Lhs, watRight+updateOp, false)
+		return c.compileAssignmentUpdateExpressionWAT(ass.Lhs, watRight, false)
 	case Expression_Literal:
 		lit := expr.Value.(LiteralExpression)
 		switch lit.Literal.Type {
@@ -425,9 +451,9 @@ func (c *Compiler) compileExpressionWAT(expr Expression) (string, error) {
 			return pushConstantNumberWAT(lit.Literal.Primitive, lit.Literal.Value), nil
 		case Literal_Boolean:
 			if lit.Literal.Value.(bool) {
-				return "i32.const 1\n", nil
+				return ofInstruction("i32.const 1"), nil
 			} else {
-				return "i32.const 0\n", nil
+				return ofInstruction("i32.const 0"), nil
 			}
 		case Literal_String:
 			panic("not implemented")
@@ -435,13 +461,17 @@ func (c *Compiler) compileExpressionWAT(expr Expression) (string, error) {
 	case Expression_VariableReference:
 		ref := expr.Value.(VariableReferenceExpression)
 
-		cast := ""
+		cast := emptyCode()
 		if expr.ValueType.Type == Type_Primitive {
 			// TODO: technically only needed for function parameters because functions can be called from outside WASM so they might not be fully type checked
 			cast = getTypeCast(expr.ValueType.Value.(PrimitiveType))
 		}
 
-		return "local.get $" + strconv.Itoa(getLocal(c.CurrentBlock, ref.Variable).Index) + "\n" + cast, nil
+		code := emptyCode()
+		code.add("local.get $" + strconv.Itoa(getLocal(c.CurrentBlock, ref.Variable).Index))
+		code.addAll(cast)
+
+		return code, nil
 	case Expression_Binary:
 		binary := expr.Value.(BinaryExpression)
 
@@ -451,39 +481,39 @@ func (c *Compiler) compileExpressionWAT(expr Expression) (string, error) {
 
 		watLeft, err := c.compileExpressionWAT(binary.Left)
 		if err != nil {
-			return "", err
+			return emptyCode(), err
 		}
 
 		watRight, err := c.compileExpressionWAT(binary.Right)
 		if err != nil {
-			return "", err
+			return emptyCode(), err
 		}
 
 		op := c.compileOperationWAT(binary.Operation, operandType)
 
-		return watLeft + watRight + op + getTypeCast(exprType), nil
+		return concat(watLeft, watRight, op, getTypeCast(exprType)), nil
 	case Expression_Tuple:
 		tuple := expr.Value.(TupleExpression)
 
-		wat := ""
+		wat := emptyCode()
 		for _, member := range tuple.Members {
 			memberWAT, err := c.compileExpressionWAT(member)
 			if err != nil {
-				return "", err
+				return emptyCode(), err
 			}
 
-			wat += memberWAT
+			wat.addAll(memberWAT)
 		}
 
 		return wat, nil
 	case Expression_FunctionCall:
 		fc := expr.Value.(FunctionCallExpression)
 
-		wat := ""
+		wat := emptyCode()
 		if fc.Parameters != nil {
 			wat, err = c.compileExpressionWAT(*fc.Parameters)
 			if err != nil {
-				return "", err
+				return emptyCode(), err
 			}
 		}
 
@@ -492,39 +522,40 @@ func (c *Compiler) compileExpressionWAT(expr Expression) (string, error) {
 			if !c.Wasm64 {
 				cast, err := castPrimitiveWAT(Primitive_U64, Primitive_U32)
 				if err != nil {
-					return "", err
+					return emptyCode(), err
 				}
 
-				wat += cast
+				wat.addAll(cast)
 			}
 
-			wat += "memory.grow\n"
+			wat.add("memory.grow")
 
 			if !c.Wasm64 {
 				cast, err := castPrimitiveWAT(Primitive_I32, Primitive_I64)
 				if err != nil {
-					return "", err
+					return emptyCode(), err
 				}
 
-				wat += cast
+				wat.addAll(cast)
 			}
 
 			return wat, nil
 		case BUILTIN_MEMORY_SIZE:
-			wat += "memory.size\n"
+			wat.add("memory.size")
 
 			if !c.Wasm64 {
 				cast, err := castPrimitiveWAT(Primitive_U32, Primitive_U64)
 				if err != nil {
-					return "", err
+					return emptyCode(), err
 				}
 
-				wat += cast
+				wat.addAll(cast)
 			}
 
 			return wat, nil
 		default:
-			return wat + "call $" + fc.Function + "\n", nil
+			wat.add("call $" + fc.Function)
+			return wat, nil
 		}
 	case Expression_Unary:
 		unary := expr.Value.(UnaryExpression)
@@ -532,35 +563,46 @@ func (c *Compiler) compileExpressionWAT(expr Expression) (string, error) {
 
 		wat, err := c.compileExpressionWAT(unary.Value)
 		if err != nil {
-			return "", err
+			return emptyCode(), err
 		}
 
 		watType := getPrimitiveWATType(exprType)
 		switch unary.Operation {
 		case UnaryOperation_Negate:
 			if isFloatingPoint(exprType) {
-				return wat + watType + ".neg\n", nil
+				wat.add(watType + ".neg")
+				return wat, nil
 			} else {
-				return watType + ".const 0\n" + wat + watType + ".sub\n" + getTypeCast(exprType), nil
+				code := emptyCode()
+				code.add(watType + ".const 0")
+				code.addAll(wat)
+				code.add(watType + ".sub")
+				code.addAll(getTypeCast(exprType))
+				return code, nil
 			}
 		case UnaryOperation_Nop:
 			return wat, nil
 		case UnaryOperation_BitwiseNot:
 			if getBits(exprType) == 64 {
-				return wat + watType + ".const 0xFFFFFFFFFFFFFFFF\n" + watType + ".xor\n" + getTypeCast(exprType), nil
+				wat.add(watType + ".const 0xFFFFFFFFFFFFFFFF")
 			} else {
-				return wat + watType + ".const 0xFFFFFFFF\n" + watType + ".xor\n" + getTypeCast(exprType), nil
+				wat.add(watType + ".const 0xFFFFFFFF")
 			}
+
+			wat.add(watType + ".xor")
+			wat.addAll(getTypeCast(exprType))
+			return wat, nil
 		case UnaryOperation_LogicalNot:
-			return wat + "i32.eqz\n", nil
+			wat.add("i32.eqz")
+			return wat, nil
 		case UnaryOperation_PreIncrement, UnaryOperation_PreDecrement, UnaryOperation_PostIncrement, UnaryOperation_PostDecrement:
 			valueType := c.getWATType(*unary.Value.ValueType)
 
-			updateWAT := valueType + ".const 1\n"
+			updateWAT := ofInstruction(valueType + ".const 1")
 			if unary.Operation == UnaryOperation_PreIncrement || unary.Operation == UnaryOperation_PostIncrement {
-				updateWAT += valueType + ".add\n"
+				updateWAT.add(valueType + ".add")
 			} else {
-				updateWAT += valueType + ".sub\n"
+				updateWAT.add(valueType + ".sub")
 			}
 
 			return c.compileAssignmentUpdateExpressionWAT(unary.Value, updateWAT, unary.Operation == UnaryOperation_PostIncrement || unary.Operation == UnaryOperation_PostDecrement)
@@ -570,7 +612,7 @@ func (c *Compiler) compileExpressionWAT(expr Expression) (string, error) {
 
 		wat, err := c.compileExpressionWAT(cast.Value)
 		if err != nil {
-			return "", err
+			return emptyCode(), err
 		}
 
 		// TODO: fine, as it is currently only allowed for primitive types
@@ -578,20 +620,20 @@ func (c *Compiler) compileExpressionWAT(expr Expression) (string, error) {
 		toType := cast.Type.Value.(PrimitiveType)
 		castWAT, err := castPrimitiveWAT(fromType, toType)
 		if err != nil {
-			return "", err
+			return emptyCode(), err
 		}
 
-		return wat + castWAT, nil
+		return concat(wat, castWAT), nil
 	case Expression_RawMemoryReference:
 		raw := expr.Value.(RawMemoryReferenceExpression)
 
 		wat, err := c.compileExpressionWAT(raw.Address)
 		if err != nil {
-			return "", err
+			return emptyCode(), err
 		}
 
 		if raw.Type.Type == Type_Primitive {
-			wat += c.getWATType(raw.Type) + ".load\n" // TODO: use load8/load16(_s/u) for smaller types
+			wat.add(c.getWATType(raw.Type) + ".load") // TODO: use load8/load16(_s/u) for smaller types
 		}
 
 		return wat, nil
@@ -606,60 +648,66 @@ func (c *Compiler) compileExpressionWAT(expr Expression) (string, error) {
 
 		arrayWAT, err := c.compileExpressionWAT(array.Array)
 		if err != nil {
-			return "", err
+			return emptyCode(), err
 		}
 
-		arrayWAT += "local.set $" + strconv.Itoa(localArray.Index) + "\n"
+		arrayWAT.add("local.set $" + strconv.Itoa(localArray.Index))
 
 		indexWAT, err := c.compileExpressionWAT(array.Index)
 		if err != nil {
-			return "", err
+			return emptyCode(), err
 		}
 
 		if !c.Wasm64 {
 			cast, err := castPrimitiveWAT(Primitive_I64, Primitive_I32)
 			if err != nil {
-				return "", err
+				return emptyCode(), err
 			}
 
-			indexWAT += cast
+			indexWAT.addAll(cast)
 		}
 
-		indexWAT += "local.set $" + strconv.Itoa(localIndex.Index) + "\n"
+		indexWAT.add("local.set $" + strconv.Itoa(localIndex.Index))
 
-		wat := arrayWAT + indexWAT
+		wat := concat(arrayWAT, indexWAT)
 
 		if _, ok := c.CompileOptions[COMPILE_OPTION_NO_BOUNDS_CHECK]; !ok {
 			// Error if index < 0
-			wat += "block\n"
+			wat.add(
-			wat += "local.get $" + strconv.Itoa(localIndex.Index) + "\n"
+				"block",
-			wat += c.getAddressWATType() + ".const 0\n"
+				"local.get $"+strconv.Itoa(localIndex.Index),
-			wat += c.getAddressWATType() + ".ge_s\n"
+				c.getAddressWATType()+".const 0",
-			wat += "br_if 0\n"
+				c.getAddressWATType()+".ge_s",
-			wat += "call $__builtin_panic\n"
+				"br_if 0",
-			wat += "end\n"
+				"call $__builtin_panic",
+				"end",
+			)
 
 			// Error if index >= array length
-			wat += "block\n"
+			wat.add(
-			wat += "local.get $" + strconv.Itoa(localIndex.Index) + "\n"
+				"block",
-			wat += "local.get $" + strconv.Itoa(localArray.Index) + "\n"
+				"local.get $"+strconv.Itoa(localIndex.Index),
-			wat += "i32.load\n" // Load array length
+				"local.get $"+strconv.Itoa(localArray.Index),
-			wat += c.getAddressWATType() + ".lt_s\n"
+				"i32.load", // Load array length
-			wat += "br_if 0\n"
+				c.getAddressWATType()+".lt_s",
-			wat += "call $__builtin_panic\n"
+				"br_if 0",
-			wat += "end\n"
+				"call $__builtin_panic",
+				"end",
+			)
 		}
 
 		elementType := array.Array.ValueType.Value.(ArrayType).ElementType
-		wat += "local.get $" + strconv.Itoa(localIndex.Index) + "\n"
+		wat.add(
-		wat += c.getAddressWATType() + ".const " + strconv.Itoa(c.getTypeSizeBytes(elementType)) + "\n"
+			"local.get $"+strconv.Itoa(localIndex.Index),
-		wat += c.getAddressWATType() + ".mul\n"
+			c.getAddressWATType()+".const "+strconv.Itoa(c.getTypeSizeBytes(elementType)),
-		wat += "local.get $" + strconv.Itoa(localArray.Index) + "\n"
+			c.getAddressWATType()+".mul",
-		wat += c.getAddressWATType() + ".add\n"
+			"local.get $"+strconv.Itoa(localArray.Index),
-		wat += c.getAddressWATType() + ".const 4\n" // first 4 bytes = length
+			c.getAddressWATType()+".add",
-		wat += c.getAddressWATType() + ".add\n"
+			c.getAddressWATType()+".const 4", // first 4 bytes = length
+			c.getAddressWATType()+".add",
+		)
 
-		wat += c.getWATType(elementType) + ".load\n" // TODO: use load8/load16(_s/u) for smaller types
+		wat.add(c.getWATType(elementType) + ".load") // TODO: use load8/load16(_s/u) for smaller types
 
 		return wat, nil
 	}
@@ -667,10 +715,10 @@ func (c *Compiler) compileExpressionWAT(expr Expression) (string, error) {
 	panic("expr not implemented")
 }
 
-func (c *Compiler) compileOperationWAT(operation Operation, operandType PrimitiveType) string {
+func (c *Compiler) compileOperationWAT(operation Operation, operandType PrimitiveType) Code {
-	op := ""
+	var op string
 
-	suffix := ""
+	var suffix string
 	if isUnsignedInt(operandType) {
 		suffix = "u"
 	} else {
@@ -679,41 +727,41 @@ func (c *Compiler) compileOperationWAT(operation Operation, operandType Primitiv
 
 	switch operation {
 	case Operation_Add:
-		op = getPrimitiveWATType(operandType) + ".add\n"
+		op = getPrimitiveWATType(operandType) + ".add"
 	case Operation_Sub:
-		op = getPrimitiveWATType(operandType) + ".sub\n"
+		op = getPrimitiveWATType(operandType) + ".sub"
 	case Operation_Mul:
-		op = getPrimitiveWATType(operandType) + ".mul\n"
+		op = getPrimitiveWATType(operandType) + ".mul"
 	case Operation_Div:
-		op = getPrimitiveWATType(operandType) + ".div_" + suffix + "\n"
+		op = getPrimitiveWATType(operandType) + ".div_" + suffix
 	case Operation_Mod:
-		op = getPrimitiveWATType(operandType) + ".rem_" + suffix + "\n"
+		op = getPrimitiveWATType(operandType) + ".rem_" + suffix
 	case Operation_Greater:
-		op = getPrimitiveWATType(operandType) + ".gt_" + suffix + "\n"
+		op = getPrimitiveWATType(operandType) + ".gt_" + suffix
 	case Operation_Less:
-		op = getPrimitiveWATType(operandType) + ".lt_" + suffix + "\n"
+		op = getPrimitiveWATType(operandType) + ".lt_" + suffix
 	case Operation_GreaterEquals:
-		op = getPrimitiveWATType(operandType) + ".ge_" + suffix + "\n"
+		op = getPrimitiveWATType(operandType) + ".ge_" + suffix
 	case Operation_LessEquals:
-		op = getPrimitiveWATType(operandType) + ".le_" + suffix + "\n"
+		op = getPrimitiveWATType(operandType) + ".le_" + suffix
 	case Operation_NotEquals:
-		op = getPrimitiveWATType(operandType) + ".ne\n"
+		op = getPrimitiveWATType(operandType) + ".ne"
 	case Operation_Equals:
-		op = getPrimitiveWATType(operandType) + ".eq\n"
+		op = getPrimitiveWATType(operandType) + ".eq"
 	default:
 		panic("operation not implemented")
 	}
 
-	return op
+	return ofInstruction(op)
 }
 
-func (c *Compiler) compileStatementWAT(stmt Statement, block *Block) (string, error) {
+func (c *Compiler) compileStatementWAT(stmt Statement, block *Block) (Code, error) {
 	switch stmt.Type {
 	case Statement_Expression:
 		expr := stmt.Value.(ExpressionStatement)
 		wat, err := c.compileExpressionWAT(expr.Expression)
 		if err != nil {
-			return "", err
+			return emptyCode(), err
 		}
 
 		numItems := 0
@@ -725,85 +773,91 @@ func (c *Compiler) compileStatementWAT(stmt Statement, block *Block) (string, er
 			}
 		}
 
-		return wat + strings.Repeat("drop\n", numItems), nil
+		for _ = range numItems {
+			wat.add("drop")
+		}
+
+		return wat, nil
 	case Statement_Block:
 		block := stmt.Value.(BlockStatement)
 		wat, err := c.compileBlockWAT(block.Block)
 		if err != nil {
-			return "", err
+			return emptyCode(), err
 		}
 
 		return wat, nil
 	case Statement_Return:
 		ret := stmt.Value.(ReturnStatement)
 
-		wat := ""
+		wat := emptyCode()
 		if ret.Value != nil {
 			valueWAT, err := c.compileExpressionWAT(*ret.Value)
 			if err != nil {
-				return "", err
+				return emptyCode(), err
 			}
 
-			wat += valueWAT
+			wat.addAll(valueWAT)
 		}
 
-		return wat + "return\n", nil
+		wat.add("return")
+		return wat, nil
 	case Statement_DeclareLocalVariable:
 		dlv := stmt.Value.(DeclareLocalVariableStatement)
 		if dlv.Initializer == nil {
-			return "", nil
+			return emptyCode(), nil
 		}
 
 		wat, err := c.compileExpressionWAT(*dlv.Initializer)
 		if err != nil {
-			return "", err
+			return emptyCode(), err
 		}
 
-		return wat + "local.set $" + strconv.Itoa(block.Locals[dlv.Variable].Index) + "\n", nil
+		wat.add("local.set $" + strconv.Itoa(block.Locals[dlv.Variable].Index))
+		return wat, nil
 	case Statement_If:
 		ifS := stmt.Value.(IfStatement)
 
 		conditionWAT, err := c.compileExpressionWAT(ifS.Condition)
 		if err != nil {
-			return "", err
+			return emptyCode(), err
 		}
 
 		condBlockWAT, err := c.compileBlockWAT(ifS.ConditionalBlock)
 		if err != nil {
-			return "", err
+			return emptyCode(), err
 		}
 
-		wat := ""
+		wat := emptyCode()
 
 		if ifS.ElseBlock != nil {
-			wat += "block\n"
+			wat.add("block")
 		}
 
 		// condition
-		wat += "block\n"
+		wat.add("block")
 
-		wat += conditionWAT
+		wat.addAll(conditionWAT)
-		wat += "i32.eqz\n" // logical not
+		wat.add("i32.eqz") // logical not
-		wat += "br_if 0\n"
+		wat.add("br_if 0")
 
 		// condition is true
-		wat += condBlockWAT
+		wat.addAll(condBlockWAT)
 
 		if ifS.ElseBlock != nil {
-			wat += "br 1\n" // jump over else block
+			wat.add("br 1") // jump over else block
 		}
 
-		wat += "end\n"
+		wat.add("end")
 
 		if ifS.ElseBlock != nil {
 			// condition is false
 			elseWAT, err := c.compileBlockWAT(ifS.ElseBlock)
 			if err != nil {
-				return "", err
+				return emptyCode(), err
 			}
 
-			wat += elseWAT
+			wat.addAll(elseWAT)
-			wat += "end\n"
+			wat.add("end")
 		}
 
 		return wat, nil
@@ -812,26 +866,27 @@ func (c *Compiler) compileStatementWAT(stmt Statement, block *Block) (string, er
 
 		conditionWAT, err := c.compileExpressionWAT(while.Condition)
 		if err != nil {
-			return "", err
+			return emptyCode(), err
 		}
 
 		bodyWAT, err := c.compileBlockWAT(while.Body)
 		if err != nil {
-			return "", err
+			return emptyCode(), err
 		}
 
-		wat := "block\n"
+		wat := emptyCode()
-		wat += "loop\n"
+		wat.add("block")
+		wat.add("loop")
 
-		wat += conditionWAT
+		wat.addAll(conditionWAT)
-		wat += "i32.eqz\n"
+		wat.add("i32.eqz")
-		wat += "br_if 1\n"
+		wat.add("br_if 1")
 
-		wat += bodyWAT
+		wat.addAll(bodyWAT)
-		wat += "br 0\n"
+		wat.add("br 0")
 
-		wat += "end\n"
+		wat.add("end")
-		wat += "end\n"
+		wat.add("end")
 
 		return wat, nil
 	}
@@ -839,17 +894,17 @@ func (c *Compiler) compileStatementWAT(stmt Statement, block *Block) (string, er
 	panic("stmt not implemented")
 }
 
-func (c *Compiler) compileBlockWAT(block *Block) (string, error) {
+func (c *Compiler) compileBlockWAT(block *Block) (Code, error) {
-	blockWAT := ""
+	blockWAT := emptyCode()
 
 	for _, stmt := range block.Statements {
 		c.CurrentBlock = block
 		wat, err := c.compileStatementWAT(stmt, block)
 		if err != nil {
-			return "", err
+			return emptyCode(), err
 		}
 
-		blockWAT += wat
+		blockWAT.addAll(wat)
 	}
 
 	return blockWAT, nil
@@ -890,14 +945,15 @@ func (c *Compiler) compileFunctionWAT(function *ParsedFunction) (string, error)
 		funcWAT += "\t(local $" + strconv.Itoa(local.Index) + " " + c.getWATType(local.Type) + ")\n"
 	}
 
-	return funcWAT + blockWat + ")\n", nil
+	return funcWAT + blockWat.toString() + ")\n", nil
 }
 
 func (c *Compiler) compile() (string, error) {
-	module := "(module (memory $memory 0) (export \"memory\" (memory $memory))\n"
+	module := "(module\n"
+	module += "(memory $memory 0) (export \"memory\" (memory $memory))\n"
 
 	module += "(func $__builtin_panic\n"
-	module += "unreachable\n"
+	module += "\tunreachable\n"
 	module += ")\n"
 
 	for _, file := range c.Files {

compiler.go

@@ -0,0 +1,66 @@
+package main
+
+import "strings"
+
+type Code struct {
+	Instructions []string
+}
+
+func (code *Code) add(instructions ...string) {
+	code.Instructions = append(code.Instructions, instructions...)
+}
+
+func (code *Code) addAll(other Code) {
+	code.Instructions = append(code.Instructions, other.Instructions...)
+}
+
+func ofInstruction(instructions ...string) Code {
+	return Code{Instructions: instructions}
+}
+
+func emptyCode() Code {
+	return Code{Instructions: []string{}}
+}
+
+func clone(code Code) Code {
+	newInstrs := make([]string, len(code.Instructions))
+	copy(newInstrs, code.Instructions)
+	return Code{Instructions: newInstrs}
+}
+
+func concat(code Code, other ...Code) Code {
+	newCode := clone(code)
+
+	for _, o := range other {
+		newCode.addAll(o)
+	}
+
+	return newCode
+}
+
+func (code Code) clone() Code {
+	return clone(code)
+}
+
+func (code *Code) isEmpty() bool {
+	return len(code.Instructions) == 0
+}
+
+func (code *Code) toString() string {
+	text := ""
+
+	indent := 1
+	for _, instr := range code.Instructions {
+		if instr == "end" {
+			indent--
+		}
+
+		text += strings.Repeat("\t", indent) + instr + "\n"
+
+		if instr == "block" || instr == "loop" {
+			indent++
+		}
+	}
+
+	return text
+}

go.mod

@@ -1,3 +1,3 @@
 module git.cringe-studios.com/mr/elysium
 
-go 1.21.7
+go 1.23.2