Add structured coroutines and explicit error handling

internal/lang/ast.go

@@ -71,6 +71,7 @@ type FunctionSignature struct {
 	Name       string
 	Params     []Param
 	ReturnType string
+	Suspend    bool
 }
 
 type FunctionDecl struct {
@@ -78,6 +79,7 @@ type FunctionDecl struct {
 	Params     []Param
 	ReturnType string
 	Body       []Stmt
+	Suspend    bool
 }
 
 type Param struct {
@@ -290,6 +292,21 @@ type SelectorExpr struct {
 
 func (SelectorExpr) exprNode() {}
 
+type SafeSelectorExpr struct {
+	Receiver Expr
+	Name     string
+}
+
+func (SafeSelectorExpr) exprNode() {}
+
+type NonNullExpr struct{ Value Expr }
+
+func (NonNullExpr) exprNode() {}
+
+type TryExpr struct{ Value Expr }
+
+func (TryExpr) exprNode() {}
+
 type IndexExpr struct {
 	Receiver Expr
 	Index    Expr