all: implement scoped defer (part 1)

vlib/v/ast/ast.v

@@ -221,6 +221,7 @@ pub struct Block {
 pub:
 	is_unsafe bool
 	pos       token.Pos
+	scope     &Scope
 pub mut:
 	stmts []Stmt
 }
@@ -808,6 +809,7 @@ pub struct BranchStmt {
 pub:
 	kind  token.Kind
 	label string
+	scope &Scope
 	pos   token.Pos
 }
 
@@ -887,6 +889,7 @@ pub mut:
 // function return statement
 pub struct Return {
 pub:
+	scope    &Scope
 	pos      token.Pos
 	comments []Comment
 pub mut:
@@ -1326,6 +1329,7 @@ pub:
 	is_else       bool
 	is_timeout    bool
 	post_comments []Comment
+	scope         &Scope
 pub mut:
 	stmt  Stmt   // `a := <-ch` or `ch <- a`
 	stmts []Stmt // right side
@@ -1542,13 +1546,20 @@ pub:
 	is_markused   bool
 }
 
+pub enum DeferMode {
+	scoped // default
+	function
+}
+
 // TODO: handle this differently
 // v1 excludes non current os ifdefs so
 // the defer's never get added in the first place
 @[minify]
 pub struct DeferStmt {
 pub:
-	pos token.Pos
+	pos   token.Pos
+	scope &Scope
+	mode  DeferMode
 pub mut:
 	stmts      []Stmt
 	defer_vars []Ident

vlib/v/ast/scope.v

@@ -3,6 +3,10 @@
 // that can be found in the LICENSE file.
 module ast
 
+pub const empty_scope = &Scope{
+	parent: unsafe { nil }
+}
+
 @[heap]
 pub struct Scope {
 pub mut:
@@ -251,6 +255,11 @@ pub fn (s &Scope) contains(pos int) bool {
 	return pos >= s.start_pos && pos <= s.end_pos
 }
 
+@[inline]
+pub fn (s &Scope) == (o &Scope) bool {
+	return s.start_pos == o.start_pos && s.end_pos == o.end_pos
+}
+
 pub fn (s &Scope) has_inherited_vars() bool {
 	for _, obj in s.objects {
 		if obj is Var {

vlib/v/checker/fn.v

@@ -502,7 +502,8 @@ fn (mut c Checker) fn_decl(mut node ast.FnDecl) {
 				node.stmts.last().pos
 			}
 			node.stmts << ast.Return{
-				pos: return_pos // node.pos
+				scope: node.scope
+				pos:   return_pos // node.pos
 			}
 		}
 	}
@@ -512,7 +513,8 @@ fn (mut c Checker) fn_decl(mut node ast.FnDecl) {
 		sym := c.table.sym(node.return_type)
 		if sym.kind == .void {
 			node.stmts << ast.Return{
-				pos: node.pos
+				scope: node.scope
+				pos:   node.pos
 			}
 		}
 	}

vlib/v/checker/lambda_expr.v

@@ -70,6 +70,7 @@ pub fn (mut c Checker) lambda_expr(mut node ast.LambdaExpr, exp_typ ast.Type) as
 			}
 		} else {
 			stmts << ast.Return{
+				scope: node.scope
 				pos:   node.pos
 				exprs: [node.expr]
 			}

vlib/v/checker/tests/invalid_defer_mode_err.out

@@ -0,0 +1,6 @@
+vlib/v/checker/tests/invalid_defer_mode_err.vv:4:8: error: unknown `defer` mode: `fn1`
+    2 |     defer {} // ok
+    3 |     defer(fn) {} // ok
+    4 |     defer(fn1) {} // fail
+      |           ~~~
+    5 | }

vlib/v/checker/tests/invalid_defer_mode_err.vv

@@ -0,0 +1,5 @@
+fn main() {
+	defer {} // ok
+	defer(fn) {} // ok
+	defer(fn1) {} // fail
+}

vlib/v/fmt/fmt.v

@@ -981,12 +981,15 @@ pub fn (mut f Fmt) const_decl(node ast.ConstDecl) {
 }
 
 fn (mut f Fmt) defer_stmt(node ast.DeferStmt) {
-	f.write('defer ')
+	f.write('defer')
+	if node.mode == .function {
+		f.write('(fn)')
+	}
 	if node.stmts.len == 0 {
-		f.writeln('{}')
+		f.writeln(' {}')
 	} else if node.stmts.len == 1 && node.pos.line_nr == node.pos.last_line
 		&& stmt_is_single_line(node.stmts[0]) {
-		f.write('{ ')
+		f.write(' { ')
 		// the control stmts (return/break/continue...) print a newline inside them,
 		// so, since this'll all be on one line, trim any possible whitespace
 		str := f.node_str(node.stmts[0]).trim_space()
@@ -1000,7 +1003,7 @@ fn (mut f Fmt) defer_stmt(node ast.DeferStmt) {
 		// f.stmt(node.stmts[0])
 		f.writeln(' }')
 	} else {
-		f.writeln('{')
+		f.writeln(' {')
 		f.stmts(node.stmts)
 		f.writeln('}')
 	}

vlib/v/fmt/tests/defer_mode_expected.vv

@@ -0,0 +1,16 @@
+fn main() {
+	defer(fn) { println('${@FN} - 0 - defer') }
+	{
+		defer { println('${@FN} - 1 - defer') }
+		{
+			defer { println('${@FN} - 2 - defer') }
+			println('exit fn main().scope.2')
+		}
+		println('exit fn main().scope.1')
+	}
+
+	defer(fn) {
+		println('defer(fn)')
+	}
+	println('exit fn main().scope.0')
+}

vlib/v/fmt/tests/defer_mode_input.vv

@@ -0,0 +1,17 @@
+fn main() {
+	defer  (fn) { println('${@FN} - 0 - defer') }
+	{
+		defer { println('${@FN} - 1 - defer') }
+		{
+			defer { println('${@FN} - 2 - defer') }
+			println('exit fn main().scope.2')
+		}
+		println('exit fn main().scope.1')
+	}
+	defer
+	(fn)
+	{
+		println('defer(fn)')
+	}
+	println('exit fn main().scope.0')
+}