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:
@@ -1548,7 +1551,8 @@ pub:
 @[minify]
 pub struct DeferStmt {
 pub:
-	pos token.Pos
+	pos   token.Pos
+	scope &Scope
 pub mut:
 	stmts      []Stmt
 	defer_vars []Ident

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/gen/c/cgen.v

@@ -2549,6 +2549,11 @@ fn (mut g Gen) stmt(node ast.Stmt) {
 				}
 			}
 			g.stmts(node.stmts)
+			if g.pref.scoped_defer {
+				if node.scope != unsafe { nil } {
+					g.write_defer_stmts_when_needed(node.scope, false)
+				}
+			}
 			g.writeln('}')
 			if node.is_unsafe {
 				g.unsafe_level--
@@ -2655,7 +2660,9 @@ fn (mut g Gen) stmt(node ast.Stmt) {
 		ast.DeferStmt {
 			mut defer_stmt := node
 			defer_stmt.ifdef = g.defer_ifdef
-			g.writeln('${g.defer_flag_var(defer_stmt)} = true;')
+			if !g.pref.scoped_defer {
+				g.writeln('${g.defer_flag_var(defer_stmt)} = true;')
+			}
 			g.defer_stmts << defer_stmt
 		}
 		ast.EnumDecl {
@@ -2762,30 +2769,6 @@ fn (mut g Gen) stmt(node ast.Stmt) {
 	// `foo('a' + 'b')` => `tmp := 'a' + 'b'; foo(tmp); string_free(&tmp);`
 }
 
-fn (mut g Gen) write_defer_stmts() {
-	for i := g.defer_stmts.len - 1; i >= 0; i-- {
-		defer_stmt := g.defer_stmts[i]
-		if !g.pref.is_prod {
-			g.writeln('// Defer begin')
-		}
-		g.writeln('if (${g.defer_flag_var(defer_stmt)}) {')
-
-		//		g.indent++
-		if defer_stmt.ifdef.len > 0 {
-			g.writeln(defer_stmt.ifdef)
-			g.stmts(defer_stmt.stmts)
-			g.writeln2('', '#endif')
-		} else {
-			g.stmts(defer_stmt.stmts)
-		}
-		//		g.indent--
-		g.writeln('}')
-		if !g.pref.is_prod {
-			g.writeln('// Defer end')
-		}
-	}
-}
-
 struct SumtypeCastingFn {
 	fn_name string
 	got     ast.Type
@@ -5036,6 +5019,9 @@ fn (mut g Gen) lock_expr(node ast.LockExpr) {
 	if node.is_expr {
 		g.writeln(';')
 	}
+	if g.pref.scoped_defer {
+		g.write_defer_stmts(node.scope, false)
+	}
 	g.writeln('}')
 	g.unlock_locks()
 	if node.is_expr {
@@ -6029,6 +6015,9 @@ fn (mut g Gen) branch_stmt(node ast.BranchStmt) {
 			}
 			else {}
 		}
+		if g.pref.scoped_defer {
+			g.write_defer_stmts(node.scope, false)
+		}
 		// continue or break
 		if g.is_autofree && !g.is_builtin_mod {
 			g.trace_autofree('// free before continue/break')
@@ -6081,7 +6070,7 @@ fn (mut g Gen) return_stmt(node ast.Return) {
 		&& !fn_ret_type.has_option_or_result()
 	mut has_semicolon := false
 	if exprs_len == 0 {
-		g.write_defer_stmts_when_needed()
+		g.write_defer_stmts_when_needed(node.scope, true)
 		if fn_return_is_option || fn_return_is_result {
 			styp := g.styp(fn_ret_type)
 			if g.is_autofree {
@@ -6109,10 +6098,10 @@ fn (mut g Gen) return_stmt(node ast.Return) {
 			g.write('${ret_typ} ${tmpvar} = ')
 			g.expr(expr0)
 			g.writeln(';')
-			g.write_defer_stmts_when_needed()
+			g.write_defer_stmts_when_needed(node.scope, true)
 			g.writeln('return ${tmpvar};')
 		} else {
-			g.write_defer_stmts_when_needed()
+			g.write_defer_stmts_when_needed(node.scope, true)
 			g.write('return ')
 			g.expr(expr0)
 			g.writeln(';')
@@ -6135,7 +6124,7 @@ fn (mut g Gen) return_stmt(node ast.Return) {
 				g.write('${ret_typ} ${test_error_var} = ')
 				g.gen_option_error(fn_ret_type, expr0)
 				g.writeln(';')
-				g.write_defer_stmts_when_needed()
+				g.write_defer_stmts_when_needed(node.scope, true)
 				g.gen_failing_return_error_for_test_fn(node, test_error_var)
 				return
 			}
@@ -6158,7 +6147,7 @@ fn (mut g Gen) return_stmt(node ast.Return) {
 						}
 					}
 				}
-				g.write_defer_stmts_when_needed()
+				g.write_defer_stmts_when_needed(node.scope, true)
 				g.writeln('return ${tmpvar};')
 			}
 			return
@@ -6174,7 +6163,7 @@ fn (mut g Gen) return_stmt(node ast.Return) {
 				g.write('${ret_typ} ${test_error_var} = ')
 				g.gen_result_error(fn_ret_type, expr0)
 				g.writeln(';')
-				g.write_defer_stmts_when_needed()
+				g.write_defer_stmts_when_needed(node.scope, true)
 				g.gen_failing_return_error_for_test_fn(node, test_error_var)
 				return
 			}
@@ -6186,7 +6175,7 @@ fn (mut g Gen) return_stmt(node ast.Return) {
 			g.gen_result_error(fn_ret_type, expr0)
 			g.writeln(';')
 			if use_tmp_var {
-				g.write_defer_stmts_when_needed()
+				g.write_defer_stmts_when_needed(node.scope, true)
 				g.writeln('return ${tmpvar};')
 			}
 			return
@@ -6199,7 +6188,7 @@ fn (mut g Gen) return_stmt(node ast.Return) {
 			g.write('${ret_typ} ${tmpvar} = ')
 			g.expr(expr0)
 			g.writeln(';')
-			g.write_defer_stmts_when_needed()
+			g.write_defer_stmts_when_needed(node.scope, true)
 			g.writeln('return ${tmpvar};')
 			return
 		}
@@ -6301,10 +6290,10 @@ fn (mut g Gen) return_stmt(node ast.Return) {
 		g.write('}')
 		if fn_return_is_option {
 			g.writeln(' }, (${option_name}*)(&${tmpvar}), sizeof(${styp}));')
-			g.write_defer_stmts_when_needed()
+			g.write_defer_stmts_when_needed(node.scope, true)
 		} else if fn_return_is_result {
 			g.writeln(' }, (${result_name}*)(&${tmpvar}), sizeof(${styp}));')
-			g.write_defer_stmts_when_needed()
+			g.write_defer_stmts_when_needed(node.scope, true)
 		}
 		// Make sure to add our unpacks
 		if multi_unpack != '' {
@@ -6318,7 +6307,7 @@ fn (mut g Gen) return_stmt(node ast.Return) {
 			if !has_semicolon {
 				g.writeln(';')
 			}
-			g.write_defer_stmts_when_needed()
+			g.write_defer_stmts_when_needed(node.scope, true)
 			g.writeln('return ${tmpvar};')
 			has_semicolon = true
 		} else if fn_return_is_option || fn_return_is_result {
@@ -6381,7 +6370,7 @@ fn (mut g Gen) return_stmt(node ast.Return) {
 				}
 				g.writeln(' }, (${option_name}*)(&${tmpvar}), sizeof(${styp}));')
 			}
-			g.write_defer_stmts_when_needed()
+			g.write_defer_stmts_when_needed(node.scope, true)
 			if g.is_autofree {
 				g.detect_used_var_on_return(expr0)
 			}
@@ -6429,7 +6418,7 @@ fn (mut g Gen) return_stmt(node ast.Return) {
 				}
 				g.writeln(' }, (${result_name}*)(&${tmpvar}), sizeof(${styp}));')
 			}
-			g.write_defer_stmts_when_needed()
+			g.write_defer_stmts_when_needed(node.scope, true)
 			if g.is_autofree {
 				g.detect_used_var_on_return(expr0)
 			}
@@ -6539,7 +6528,7 @@ fn (mut g Gen) return_stmt(node ast.Return) {
 		if use_tmp_var {
 			g.writeln(';')
 			has_semicolon = true
-			g.write_defer_stmts_when_needed()
+			g.write_defer_stmts_when_needed(node.scope, true)
 			if !g.is_builtin_mod {
 				g.autofree_scope_vars(node.pos.pos - 1, node.pos.line_nr, true)
 			}
@@ -7419,7 +7408,9 @@ fn (mut g Gen) or_block(var_name string, or_block ast.OrExpr, return_type ast.Ty
 			// `opt() or { return err }`
 			// Since we *do* return, first we have to ensure that
 			// the deferred statements are generated.
-			g.write_defer_stmts()
+			if or_block.scope != unsafe { nil } {
+				g.write_defer_stmts(or_block.scope, true)
+			}
 			// Now that option types are distinct we need a cast here
 			if g.fn_decl == unsafe { nil } || g.fn_decl.return_type == ast.void_type {
 				g.writeln('\treturn;')
@@ -7453,7 +7444,9 @@ fn (mut g Gen) or_block(var_name string, or_block ast.OrExpr, return_type ast.Ty
 			// `opt() or { return err }`
 			// Since we *do* return, first we have to ensure that
 			// the deferred statements are generated.
-			g.write_defer_stmts()
+			if or_block.scope != unsafe { nil } {
+				g.write_defer_stmts(or_block.scope, true)
+			}
 			// Now that option types are distinct we need a cast here
 			if g.fn_decl == unsafe { nil } || g.fn_decl.return_type == ast.void_type {
 				g.writeln('\treturn;')

vlib/v/gen/c/defer.v

@@ -0,0 +1,63 @@
+// Copyright (c) 2019-2024 Alexander Medvednikov. All rights reserved.
+// Use of this source code is governed by an MIT license
+// that can be found in the LICENSE file.
+module c
+
+import v.ast
+
+fn (g &Gen) defer_flag_var(stmt &ast.DeferStmt) string {
+	return '${g.last_fn_c_name}_defer_${stmt.idx_in_fn}'
+}
+
+@[inline]
+fn is_same_scope(a &ast.Scope, b &ast.Scope) bool {
+	return a.start_pos == b.start_pos && a.end_pos == b.end_pos
+}
+
+fn (mut g Gen) write_defer_stmts(scope &ast.Scope, lookup bool) {
+	g.indent++
+	for i := g.defer_stmts.len - 1; i >= 0; i-- {
+		defer_stmt := g.defer_stmts[i]
+		if g.pref.scoped_defer {
+			if !((lookup && defer_stmt.scope.start_pos < scope.start_pos
+				&& defer_stmt.scope.end_pos > scope.end_pos)
+				|| is_same_scope(defer_stmt.scope, scope)) {
+				// generate only `defer`s from the current scope
+				continue
+			}
+			g.writeln('{ // defer begin')
+			if defer_stmt.ifdef.len > 0 {
+				g.writeln(defer_stmt.ifdef)
+				g.stmts(defer_stmt.stmts)
+				g.writeln2('', '#endif')
+			} else {
+				g.stmts(defer_stmt.stmts)
+			}
+			g.writeln('} // defer end')
+		} else {
+			g.writeln('if (${g.defer_flag_var(defer_stmt)}) { // defer begin')
+			if defer_stmt.ifdef.len > 0 {
+				g.writeln(defer_stmt.ifdef)
+				g.stmts(defer_stmt.stmts)
+				g.writeln2('', '#endif')
+			} else {
+				g.stmts(defer_stmt.stmts)
+			}
+			g.writeln('} // defer end')
+		}
+	}
+	g.indent--
+}
+
+fn (mut g Gen) write_defer_stmts_when_needed(scope &ast.Scope, lookup bool) {
+	// unlock all mutexes, in case we are in a lock statement. defers are not
+	// allowed in lock statements.
+	g.unlock_locks()
+	if g.defer_stmts.len > 0 {
+		g.write_defer_stmts(scope, lookup)
+	}
+	if g.defer_profile_code.len > 0 {
+		g.writeln2('', '\t// defer_profile_code')
+		g.writeln2(g.defer_profile_code, '')
+	}
+}