all: change optional to result of io (#16075)

vlib/toml/ast/walker/walker.v

@@ -4,15 +4,15 @@ import toml.ast
 
 // Visitor defines a visit method which is invoked by the walker on each Value node it encounters.
 pub interface Visitor {
-	visit(value &ast.Value) ?
+	visit(value &ast.Value) !
 }
 
 // Modifier defines a modify method which is invoked by the walker on each Value node it encounters.
 pub interface Modifier {
-	modify(mut value ast.Value) ?
+	modify(mut value ast.Value) !
 }
 
-pub type InspectorFn = fn (value &ast.Value, data voidptr) ?
+pub type InspectorFn = fn (value &ast.Value, data voidptr) !
 
 struct Inspector {
 	inspector_callback InspectorFn
@@ -20,48 +20,48 @@ mut:
 	data voidptr
 }
 
-pub fn (i &Inspector) visit(value &ast.Value) ? {
+pub fn (i &Inspector) visit(value &ast.Value) ! {
 	i.inspector_callback(value, i.data) or { return err }
 }
 
 // inspect traverses and checks the AST Value node on a depth-first order and based on the data given
-pub fn inspect(value &ast.Value, data voidptr, inspector_callback InspectorFn) ? {
-	walk(Inspector{inspector_callback, data}, value)?
+pub fn inspect(value &ast.Value, data voidptr, inspector_callback InspectorFn) ! {
+	walk(Inspector{inspector_callback, data}, value)!
 }
 
 // walk traverses the AST using the given visitor
-pub fn walk(visitor Visitor, value &ast.Value) ? {
+pub fn walk(visitor Visitor, value &ast.Value) ! {
 	if value is map[string]ast.Value {
 		value_map := value as map[string]ast.Value
 		for _, val in value_map {
-			walk(visitor, &val)?
+			walk(visitor, &val)!
 		}
 	}
 	if value is []ast.Value {
 		value_array := value as []ast.Value
 		for val in value_array {
-			walk(visitor, &val)?
+			walk(visitor, &val)!
 		}
 	} else {
-		visitor.visit(value)?
+		visitor.visit(value)!
 	}
 }
 
 // walk_and_modify traverses the AST using the given modifier and lets the visitor
 // modify the contents.
-pub fn walk_and_modify(modifier Modifier, mut value ast.Value) ? {
+pub fn walk_and_modify(modifier Modifier, mut value ast.Value) ! {
 	if value is map[string]ast.Value {
 		mut value_map := value as map[string]ast.Value
 		for _, mut val in value_map {
-			walk_and_modify(modifier, mut &val)?
+			walk_and_modify(modifier, mut &val)!
 		}
 	}
 	if value is []ast.Value {
 		mut value_array := value as []ast.Value
 		for mut val in value_array {
-			walk_and_modify(modifier, mut &val)?
+			walk_and_modify(modifier, mut &val)!
 		}
 	} else {
-		modifier.modify(mut value)?
+		modifier.modify(mut value)!
 	}
 }