package typechecker
import (
"path/filepath"
"github.com/marzeq/quokka/parser"
"github.com/marzeq/quokka/shared"
"github.com/marzeq/quokka/tokeniser"
)
type (
Node = parser.Node
Type = shared.Type
)
type VarSig struct {
Type Type
Mutable bool
}
type FunctionSig struct {
ArgTypes []shared.Pair[string, Type]
RetType Type
}
type (
VarTable = *shared.SymbolTable[*VarSig]
FuncTable = *shared.SymbolTable[*FunctionSig]
)
type TypeChecker struct {
VarTable VarTable
FuncTable FuncTable
}
func NewTypeChecker() *TypeChecker {
return &TypeChecker{
VarTable: shared.NewSymbolTable[*VarSig](),
FuncTable: shared.NewSymbolTable[*FunctionSig](),
}
}
func (tc *TypeChecker) TypeCheck(root *Node) (*Node, error) {
loaded := make(map[string]*Node)
recStack := make(map[string]bool)
mergedRoot, err := tc.processImports(root, loaded, recStack)
if err != nil {
return nil, err
}
root = mergedRoot
for _, node := range root.Children {
if node.Type != parser.NODE_TYPE_FUNCTION_DEF {
continue
}
fname, funcSig, err := extractFunctionSig(node)
if err != nil {
return nil, err
}
if ok := tc.FuncTable.Define(fname, funcSig); !ok {
return nil, shared.NewError(node.Loc, "function '%s' is already defined", fname)
}
}
for _, node := range root.Children {
if node.Type != parser.NODE_TYPE_FUNCTION_DEF {
continue
}
name := identToStr(node.Value.(*parser.FunctionValue).Name)
sig, _ := tc.FuncTable.Lookup(name)
tc.enterScope()
if err := tc.typeCheckFunction(node, sig); err != nil {
return nil, err
}
tc.exitScope()
}
return mergedRoot, nil
}
func (tc *TypeChecker) processImports(root *Node, loaded map[string]*Node, recStack map[string]bool) (*Node, error) {
filePath := root.Loc.FilePath
if recStack[filePath] {
return nil, shared.NewError(root.Loc, "import cycle detected for file '%s'", filePath)
}
if merged, ok := loaded[filePath]; ok {
return merged, nil
}
recStack[filePath] = true
merged := &Node{
Type: root.Type,
Loc: root.Loc,
Children: []*Node{},
}
for _, node := range root.Children {
if node.Type != parser.NODE_TYPE_IMPORT {
continue
}
importPath := node.Right.Value.(string)
resolvedPath := filepath.Join(filepath.Dir(filePath), importPath)
t, err := tokeniser.NewTokeniserFromFile(resolvedPath)
if err != nil {
switch err.(type) {
case shared.Error:
return nil, err
default:
return nil, shared.NewError(node.Loc, "import failed: %v", err)
}
}
toks, err := t.Tokenise()
if err != nil {
return nil, err
}
p := parser.NewParser(toks)
ast, err := p.Parse()
if err != nil {
return nil, err
}
importedMerged, err := tc.processImports(ast, loaded, recStack)
if err != nil {
return nil, err
}
merged.Children = append(merged.Children, importedMerged.Children...)
}
for _, node := range root.Children {
if node.Type != parser.NODE_TYPE_IMPORT {
merged.Children = append(merged.Children, node)
}
}
loaded[filePath] = merged
delete(recStack, filePath)
return merged, nil
}
func (tc *TypeChecker) enterScope() {
tc.VarTable.EnterScope()
tc.FuncTable.EnterScope()
}
func (tc *TypeChecker) exitScope() {
tc.VarTable.ExitScope()
tc.FuncTable.ExitScope()
}
func (tc *TypeChecker) typeCheckFunction(funcNode *Node, sig *FunctionSig) error {
val := funcNode.Value.(*parser.FunctionValue)
body := funcNode.Children[0]
name := identToStr(funcNode.Value.(*parser.FunctionValue).Name)
for _, arg := range sig.ArgTypes {
tc.VarTable.Define(arg.L, &VarSig{
Type: arg.R,
Mutable: false,
})
}
if body.Type == parser.NODE_TYPE_BLOCK {
return tc.typeCheckBlock(body, sig, false)
}
exprType, err := tc.typeCheckExpression(body, sig.RetType)
if err != nil {
return err
}
if !shared.CanCoerceTo(exprType, sig.RetType) {
return shared.NewError(val.RetType.Loc, "function '%s' expects return type '%s' but returns '%s'",
name, sig.RetType, exprType)
}
if exprType == shared.BUILTIN_UNTYPED_INT {
body.ExprType = sig.RetType
}
return nil
}
func (tc *TypeChecker) typeCheckBlock(blockNode *Node, sig *FunctionSig, isLoop bool) error {
foundReturn := false
for _, node := range blockNode.Children {
switch node.Type {
case parser.NODE_TYPE_DECLARATION:
varName, varSig, err := tc.typeCheckDeclaration(node)
if err != nil {
return err
}
if ok := tc.VarTable.Define(varName, varSig); !ok {
return shared.NewError(node.Left.Loc, "variable '%s' is already declared in this scope", varName)
}
case parser.NODE_TYPE_FUNCTION_DEF:
fname, fsig, err := extractFunctionSig(node)
if err != nil {
return err
}
if ok := tc.FuncTable.Define(fname, fsig); !ok {
return shared.NewError(node.Loc, "function '%s' is already defined", fname)
}
tc.enterScope()
if err := tc.typeCheckFunction(node, fsig); err != nil {
return err
}
tc.exitScope()
case parser.NODE_TYPE_ASSIGNMENT:
if err := tc.typeCheckAssignment(node); err != nil {
return err
}
case parser.NODE_TYPE_FUNCTION_CALL:
if _, err := tc.typeCheckFunctionCall(node); err != nil {
return err
}
case parser.NODE_TYPE_CONTROL_KEYWORD:
kw := node.Value.(string)
switch kw {
case "return":
retType := shared.BUILTIN_VOID
if node.Right != nil {
var err error
retType, err = tc.typeCheckExpression(node.Right, sig.RetType)
if err != nil {
return err
}
if !shared.CanCoerceTo(retType, sig.RetType) {
return shared.NewError(node.Loc, "wrong return type for function, expected '%s' got '%s'", sig.RetType, retType)
}
if retType == shared.BUILTIN_UNTYPED_INT {
node.Right.ExprType = sig.RetType
}
}
foundReturn = true
case "break", "continue":
if !isLoop {
return shared.NewError(node.Loc, "'%s' statement outside a loop", kw)
}
}
case parser.NODE_TYPE_BLOCK:
tc.enterScope()
if err := tc.typeCheckBlock(node, sig, isLoop); err != nil {
return err
}
tc.exitScope()
case parser.NODE_TYPE_FOR:
if err := tc.typeCheckForLoop(node, sig); err != nil {
return err
}
case parser.NODE_TYPE_IF:
if err := tc.typeCheckIfStatement(node, sig); err != nil {
return err
}
default:
panic("unexpected node in block")
}
}
if !foundReturn && sig.RetType != shared.BUILTIN_VOID {
return shared.NewError(blockNode.Loc, "function with return type '%s' is missing a return statement", sig.RetType)
}
return nil
}
func (tc *TypeChecker) typeCheckExpression(exprNode *Node, expectedType Type) (Type, error) {
switch exprNode.Type {
case parser.NODE_TYPE_IDENTIFIER:
varName := exprNode.Value.(string)
varSig, ok := tc.VarTable.Lookup(varName)
if !ok {
return shared.BUILTIN_VOID, shared.NewError(exprNode.Loc, "undefined variable '%s'", varName)
}
exprNode.ExprType = varSig.Type
return varSig.Type, nil
case parser.NODE_TYPE_NUMBER_LITERAL:
exprType := shared.BUILTIN_UNTYPED_INT
if expectedType != shared.BUILTIN_VOID && shared.CanCoerceTo(exprType, expectedType) {
exprNode.ExprType = expectedType
return expectedType, nil
}
return exprType, nil
case parser.NODE_TYPE_BOOL_LITERAL:
exprNode.ExprType = shared.BUILTIN_BOOL
return shared.BUILTIN_BOOL, nil
case parser.NODE_TYPE_FUNCTION_CALL:
return tc.typeCheckFunctionCall(exprNode)
case parser.NODE_TYPE_UNARY_OP:
var op string
switch v := exprNode.Value.(type) {
case string:
if v != "not" {
return shared.BUILTIN_VOID, shared.NewError(exprNode.Loc, "invalid unary operator '%s'", v)
}
op = v
case tokeniser.TokenType:
if v == tokeniser.TOKEN_TYPE_MINUS {
op = "-"
} else {
return shared.BUILTIN_VOID, shared.NewError(exprNode.Loc, "invalid unary operator token '%v'", v)
}
default:
return shared.BUILTIN_VOID, shared.NewError(exprNode.Loc, "invalid unary operator type '%T'", exprNode.Value)
}
operandType, err := tc.typeCheckExpression(exprNode.Right, shared.BUILTIN_VOID)
if err != nil {
return shared.BUILTIN_VOID, err
}
if expectedType != shared.BUILTIN_VOID && operandType == shared.BUILTIN_UNTYPED_INT && shared.IsNumericType(expectedType) {
exprNode.Right.ExprType = expectedType
operandType = expectedType
}
switch op {
case "not":
if operandType != shared.BUILTIN_BOOL {
return shared.BUILTIN_VOID, shared.NewError(exprNode.Right.Loc, "unary operator 'not' expects a boolean operand, found '%s'", operandType)
}
return shared.BUILTIN_BOOL, nil
case "-":
if !shared.IsNumericType(operandType) {
return shared.BUILTIN_VOID, shared.NewError(exprNode.Right.Loc, "unary operator '-' requires numeric operand, found '%s'", operandType)
}
return operandType, nil
default:
return shared.BUILTIN_VOID, shared.NewError(exprNode.Loc, "unknown unary operator '%s'", op)
}
case parser.NODE_TYPE_BINARY_OP:
var op string
switch v := exprNode.Value.(type) {
case string:
if v != "and" && v != "or" {
return shared.BUILTIN_VOID, shared.NewError(exprNode.Loc, "invalid binary operator '%s'", v)
}
op = v
case tokeniser.TokenType:
op = tokenTypeToOperator(v)
if op == "" {
return shared.BUILTIN_VOID, shared.NewError(exprNode.Loc, "unsupported binary operator token '%v'", v)
}
default:
return shared.BUILTIN_VOID, shared.NewError(exprNode.Loc, "invalid binary operator type '%T'", exprNode.Value)
}
leftType, err := tc.typeCheckExpression(exprNode.Left, shared.BUILTIN_VOID)
if err != nil {
return shared.BUILTIN_VOID, err
}
rightType, err := tc.typeCheckExpression(exprNode.Right, shared.BUILTIN_VOID)
if err != nil {
return shared.BUILTIN_VOID, err
}
if expectedType != shared.BUILTIN_VOID {
if leftType == shared.BUILTIN_UNTYPED_INT && shared.IsNumericType(expectedType) {
exprNode.Left.ExprType = expectedType
leftType = expectedType
}
if rightType == shared.BUILTIN_UNTYPED_INT && shared.IsNumericType(expectedType) {
exprNode.Right.ExprType = expectedType
rightType = expectedType
}
}
switch op {
case "and", "or":
if leftType != shared.BUILTIN_BOOL || rightType != shared.BUILTIN_BOOL {
return shared.BUILTIN_VOID, shared.NewError(exprNode.Loc, "operator '%s' expects boolean operands, found '%s' and '%s'", op, leftType, rightType)
}
return shared.BUILTIN_BOOL, nil
case "==", "!=", "<", ">", "<=", ">=":
compatible, _ := shared.AreCompatibleNumericTypes(leftType, rightType)
if !compatible {
return shared.BUILTIN_VOID, shared.NewError(exprNode.Loc, "operator '%s' cannot be applied to operands of type '%s' and '%s'", op, leftType, rightType)
}
return shared.BUILTIN_BOOL, nil
case "+", "-", "*", "/":
compatible, commonType := shared.AreCompatibleNumericTypes(leftType, rightType)
if !compatible {
return shared.BUILTIN_VOID, shared.NewError(exprNode.Loc, "operator '%s' requires numeric operands, found '%s' and '%s'", op, leftType, rightType)
}
return commonType, nil
default:
return shared.BUILTIN_VOID, shared.NewError(exprNode.Loc, "unknown binary operator '%s'", op)
}
case parser.NODE_TYPE_IF_EXPR:
ifExpr := exprNode.Value.(*parser.IfNodeValue)
if ifExpr.IfBranch == nil {
return shared.BUILTIN_VOID, shared.NewError(exprNode.Loc, "if expression missing if branch")
}
condType, err := tc.typeCheckExpression(ifExpr.IfBranch.Condition, shared.BUILTIN_VOID)
if err != nil {
return shared.BUILTIN_VOID, err
}
if condType != shared.BUILTIN_BOOL {
return shared.BUILTIN_VOID, shared.NewError(ifExpr.IfBranch.Condition.Loc, "if condition must be boolean, found '%s'", condType)
}
ifType, err := tc.typeCheckExpression(ifExpr.IfBranch.Node, expectedType)
if err != nil {
return shared.BUILTIN_VOID, err
}
commonType := ifType
for _, elseIf := range ifExpr.ElseIfBranches {
elseIfCondType, err := tc.typeCheckExpression(elseIf.Condition, shared.BUILTIN_VOID)
if err != nil {
return shared.BUILTIN_VOID, err
}
if elseIfCondType != shared.BUILTIN_BOOL {
return shared.BUILTIN_VOID, shared.NewError(elseIf.Condition.Loc, "else-if condition must be boolean, found '%s'", elseIfCondType)
}
elseIfType, err := tc.typeCheckExpression(elseIf.Node, expectedType)
if err != nil {
return shared.BUILTIN_VOID, err
}
if elseIfType != commonType {
return shared.BUILTIN_VOID, shared.NewError(exprNode.Loc, "all branches must return same type, expected '%s' but found '%s'", commonType, elseIfType)
}
}
if ifExpr.ElseBranch == nil {
return shared.BUILTIN_VOID, shared.NewError(exprNode.Loc, "if expression requires else branch")
}
elseType, err := tc.typeCheckExpression(ifExpr.ElseBranch.Node, expectedType)
if err != nil {
return shared.BUILTIN_VOID, err
}
if elseType != commonType {
return shared.BUILTIN_VOID, shared.NewError(ifExpr.ElseBranch.Node.Loc, "else branch must match type '%s', found '%s'", commonType, elseType)
}
return commonType, nil
default:
return shared.BUILTIN_VOID, shared.NewError(exprNode.Loc, "unsupported expression type: '%s'", exprNode.Type)
}
}
func (tc *TypeChecker) typeCheckFunctionCall(funccallNode *Node) (Type, error) {
nameNode := funccallNode.Value.(*Node)
fname := identToStr(nameNode)
fsig, ok := tc.FuncTable.Lookup(fname)
if !ok {
return shared.BUILTIN_VOID, shared.NewError(nameNode.Loc, "undefined function '%s'", fname)
}
for i, arg := range funccallNode.Children {
fsigArgType := fsig.ArgTypes[i].R
argType, err := tc.typeCheckExpression(arg, fsigArgType)
if err != nil {
return shared.BUILTIN_VOID, err
}
if fsigArgType != argType {
return shared.BUILTIN_VOID, shared.NewError(arg.Loc,
"argument %d of function '%s' has type '%s' but expected '%s'",
i+1, fname, argType, fsig.ArgTypes[i].R,
)
}
}
funccallNode.ExprType = fsig.RetType
return fsig.RetType, nil
}
func (tc *TypeChecker) typeCheckDeclaration(declNode *Node) (string, *VarSig, error) {
varName := identToStr(declNode.Left)
info := declNode.Value.(*parser.DeclarationValue)
mutable := info.Mutable
varType := shared.BUILTIN_VOID
if info.Type != nil {
varTypeStr := identToStr(info.Type)
vt, ok := shared.ResolveType(varTypeStr)
if !ok {
return "", nil, shared.NewError(info.Type.Loc, "variable '%s' has undefined type '%s'", varName, varTypeStr)
}
varType = vt
}
exprType, err := tc.typeCheckExpression(declNode.Right, varType)
if err != nil {
return "", nil, err
}
if varType == shared.BUILTIN_VOID {
varType = exprType
} else if !shared.CanCoerceTo(exprType, varType) {
return "", nil, shared.NewError(declNode.Loc,
"cannot assign value of type '%s' to variable '%s' of type '%s'",
exprType, varName, varType,
)
}
if varType == shared.BUILTIN_UNTYPED_INT {
varType = shared.BUILTIN_I32
}
if exprType == shared.BUILTIN_UNTYPED_INT {
declNode.Right.ExprType = varType
}
return varName, &VarSig{
Type: varType,
Mutable: mutable,
}, nil
}
func (tc *TypeChecker) typeCheckAssignment(asNode *Node) error {
varName := identToStr(asNode.Left)
varSig, ok := tc.VarTable.Lookup(varName)
if !ok {
return shared.NewError(asNode.Left.Loc, "undefined variable '%s'", varName)
}
if !varSig.Mutable {
return shared.NewError(asNode.Loc, "cannot assign to immutable variable '%s'", varName)
}
exprType, err := tc.typeCheckExpression(asNode.Right, varSig.Type)
if err != nil {
return err
}
if exprType != varSig.Type {
return shared.NewError(asNode.Loc,
"cannot assign value of type '%s' to variable '%s' of type '%s'",
exprType, varName, varSig.Type,
)
}
return nil
}
func (tc *TypeChecker) typeCheckForLoop(loopNode *Node, sig *FunctionSig) error {
value := loopNode.Value.(*parser.ForLoopValue)
tc.enterScope()
for _, exOrSt := range value.ExprsOrStmts {
if exOrSt.Type.IsStatement() {
if exOrSt.Type == parser.NODE_TYPE_DECLARATION {
varName, varSig, err := tc.typeCheckDeclaration(exOrSt)
if err != nil {
return err
}
tc.VarTable.Define(varName, varSig)
} else if exOrSt.Type == parser.NODE_TYPE_ASSIGNMENT {
if err := tc.typeCheckAssignment(exOrSt); err != nil {
return err
}
} else {
return shared.NewError(exOrSt.Loc, "for loop initializer must be a declaration or assignment statement")
}
} else {
exprType, err := tc.typeCheckExpression(exOrSt, shared.BUILTIN_BOOL)
if err != nil {
return err
}
if exprType != shared.BUILTIN_BOOL {
return shared.NewError(exOrSt.Loc, "for loop condition must be a boolean expression, found '%s'", exprType)
}
}
}
if err := tc.typeCheckBlock(value.Body, sig, true); err != nil {
return err
}
tc.exitScope()
return nil
}
func (tc *TypeChecker) typeCheckIfStatement(ifNode *Node, sig *FunctionSig) error {
value := ifNode.Value.(*parser.IfNodeValue)
ifCondType, err := tc.typeCheckExpression(value.IfBranch.Condition, shared.BUILTIN_BOOL)
if err != nil {
return err
}
if ifCondType != shared.BUILTIN_BOOL {
return shared.NewError(value.ElseBranch.Condition.Loc, "if condition must be boolean, found '%s'", ifCondType)
}
if err := tc.typeCheckBlock(value.IfBranch.Node, sig, false); err != nil {
return err
}
for _, elseIfBranch := range value.ElseIfBranches {
elseIfCondType, err := tc.typeCheckExpression(elseIfBranch.Condition, shared.BUILTIN_BOOL)
if err != nil {
return err
}
if elseIfCondType != shared.BUILTIN_BOOL {
return shared.NewError(elseIfBranch.Condition.Loc, "else-if condition must be boolean, found '%s'", elseIfCondType)
}
if err := tc.typeCheckBlock(elseIfBranch.Node, sig, false); err != nil {
return err
}
}
if value.ElseBranch != nil {
if err := tc.typeCheckBlock(value.ElseBranch.Node, sig, false); err != nil {
return err
}
}
return nil
}
func extractFunctionSig(functionNode *Node) (string, *FunctionSig, error) {
functionVal := functionNode.Value.(*parser.FunctionValue)
name := identToStr(functionVal.Name)
retTypeStr := identToStr(functionVal.RetType)
retType, ok := shared.ResolveType(retTypeStr)
if !ok {
return "", nil, shared.NewError(functionVal.RetType.Loc, "function '%s' has undefined return type '%s'", name, retTypeStr)
}
argTypes := make([]shared.Pair[string, Type], len(functionVal.Args))
for i, arg := range functionVal.Args {
tpe := identToStr(arg.R)
resolved, ok := shared.ResolveType(tpe)
if !ok {
return "", nil, shared.NewError(arg.R.Loc, "parameter '%s' has undefined type '%s'", identToStr(arg.L), tpe)
}
argTypes[i] = shared.Pair[string, Type]{L: identToStr(arg.L), R: resolved}
}
return name, &FunctionSig{
ArgTypes: argTypes,
RetType: retType,
}, nil
}
func identToStr(identNode *Node) string {
return identNode.Value.(string)
}
func tokenTypeToOperator(t tokeniser.TokenType) string {
switch t {
case tokeniser.TOKEN_TYPE_PLUS:
return "+"
case tokeniser.TOKEN_TYPE_MINUS:
return "-"
case tokeniser.TOKEN_TYPE_ASTERISK:
return "*"
case tokeniser.TOKEN_TYPE_SLASH:
return "/"
case tokeniser.TOKEN_TYPE_EQUALS_EQUALS:
return "=="
case tokeniser.TOKEN_TYPE_NOT_EQUALS:
return "!="
case tokeniser.TOKEN_TYPE_LESS:
return "<"
case tokeniser.TOKEN_TYPE_GREATER:
return ">"
case tokeniser.TOKEN_TYPE_LESS_EQUALS:
return "<="
case tokeniser.TOKEN_TYPE_GREATER_EQUALS:
return ">="
default:
panic("how")
}
}