gen: implement labelled break and continue (#6880)

vlib/v/ast/ast.v

@@ -284,8 +284,9 @@ pub mut:
 // break, continue
 pub struct BranchStmt {
 pub:
-	kind token.Kind
-	pos  token.Position
+	kind  token.Kind
+	label string
+	pos   token.Position
 }
 
 pub struct CallExpr {
@@ -626,6 +627,8 @@ pub:
 	stmts  []Stmt
 	is_inf bool // `for {}`
 	pos    token.Position
+pub mut:
+	label  string // `label: for {`
 }
 
 pub struct ForInStmt {
@@ -644,6 +647,7 @@ pub mut:
 	val_type   table.Type
 	cond_type  table.Type
 	kind       table.Kind // array/map/string
+	label      string // `label: for {`
 }
 
 pub struct ForCStmt {
@@ -656,6 +660,8 @@ pub:
 	has_inc  bool
 	stmts    []Stmt
 	pos      token.Position
+pub mut:
+	label    string // `label: for {`
 }
 
 // #include etc

vlib/v/checker/checker.v

@@ -2410,6 +2410,7 @@ fn (mut c Checker) stmt(node ast.Stmt) {
 			if c.in_for_count == 0 {
 				c.error('$node.kind.str() statement not within a loop', node.pos)
 			}
+			// TODO: check any node.label is in scope for goto
 		}
 		ast.CompFor {
 			// node.typ = c.expr(node.expr)
@@ -2577,7 +2578,9 @@ fn (mut c Checker) stmt(node ast.Stmt) {
 			}
 		}
 		ast.GotoLabel {}
-		ast.GotoStmt {}
+		ast.GotoStmt {
+			// TODO: check label doesn't bypass variable declarations
+		}
 		ast.HashStmt {
 			c.hash_stmt(mut node)
 		}

vlib/v/gen/cgen.v

@@ -821,9 +821,17 @@ fn (mut g Gen) stmt(node ast.Stmt) {
 		}
 		ast.BranchStmt {
 			g.write_v_source_line_info(node.pos)
-			// continue or break
-			g.write(node.kind.str())
-			g.writeln(';')
+			if node.label.len > 0 {
+				if node.kind == .key_break {
+					g.writeln('goto $node.label\__break;')
+				} else {
+					assert node.kind == .key_continue
+					g.writeln('goto $node.label\__continue;')
+				}
+			} else {
+				// continue or break
+				g.writeln('$node.kind;')
+			}
 		}
 		ast.ConstDecl {
 			g.write_v_source_line_info(node.pos)
@@ -930,6 +938,9 @@ fn (mut g Gen) stmt(node ast.Stmt) {
 		ast.ForCStmt {
 			g.write_v_source_line_info(node.pos)
 			g.is_vlines_enabled = false
+			if node.label.len > 0 {
+				g.writeln('$node.label:')
+			}
 			g.write('for (')
 			if !node.has_init {
 				g.write('; ')
@@ -952,7 +963,13 @@ fn (mut g Gen) stmt(node ast.Stmt) {
 			g.writeln(') {')
 			g.is_vlines_enabled = true
 			g.stmts(node.stmts)
+			if node.label.len > 0 {
+				g.writeln('$node.label\__continue: {}')
+			}
 			g.writeln('}')
+			if node.label.len > 0 {
+				g.writeln('$node.label\__break: {}')
+			}
 		}
 		ast.ForInStmt {
 			g.write_v_source_line_info(node.pos)
@@ -961,6 +978,9 @@ fn (mut g Gen) stmt(node ast.Stmt) {
 		ast.ForStmt {
 			g.write_v_source_line_info(node.pos)
 			g.is_vlines_enabled = false
+			if node.label.len > 0 {
+				g.writeln('$node.label:')
+			}
 			g.writeln('for (;;) {')
 			if !node.is_inf {
 				g.indent++
@@ -972,7 +992,13 @@ fn (mut g Gen) stmt(node ast.Stmt) {
 			}
 			g.is_vlines_enabled = true
 			g.stmts(node.stmts)
+			if node.label.len > 0 {
+				g.writeln('\t$node.label\__continue: {}')
+			}
 			g.writeln('}')
+			if node.label.len > 0 {
+				g.writeln('$node.label\__break: {}')
+			}
 		}
 		ast.GlobalDecl {
 			g.global_decl(node)
@@ -1097,6 +1123,9 @@ fn (mut g Gen) write_defer_stmts() {
 }
 
 fn (mut g Gen) for_in(it ast.ForInStmt) {
+	if it.label.len > 0 {
+		g.writeln('\t$it.label: {}')
+	}
 	if it.is_range {
 		// `for x in 1..10 {`
 		i := if it.val_var == '_' { g.new_tmp_var() } else { c_name(it.val_var) }
@@ -1105,8 +1134,6 @@ fn (mut g Gen) for_in(it ast.ForInStmt) {
 		g.write('; $i < ')
 		g.expr(it.high)
 		g.writeln('; ++$i) {')
-		g.stmts(it.stmts)
-		g.writeln('}')
 	} else if it.kind == .array {
 		// `for num in nums {`
 		g.writeln('// FOR IN array')
@@ -1136,8 +1163,6 @@ fn (mut g Gen) for_in(it ast.ForInStmt) {
 				g.writeln('\t$styp ${c_name(it.val_var)} = $right;')
 			}
 		}
-		g.stmts(it.stmts)
-		g.writeln('}')
 	} else if it.kind == .array_fixed {
 		atmp := g.new_tmp_var()
 		atmp_type := g.typ(it.cond_type)
@@ -1163,8 +1188,6 @@ fn (mut g Gen) for_in(it ast.ForInStmt) {
 			}
 			g.writeln(' = (*$atmp)[$i];')
 		}
-		g.stmts(it.stmts)
-		g.writeln('}')
 	} else if it.kind == .map {
 		// `for key, val in map {`
 		g.writeln('// FOR IN map')
@@ -1201,10 +1224,17 @@ fn (mut g Gen) for_in(it ast.ForInStmt) {
 		if it.key_type == table.string_type && !g.is_builtin_mod {
 			// g.writeln('string_free(&$key);')
 		}
+		if it.label.len > 0 {
+			g.writeln('\t$it.label\__continue: {}')
+		}
 		g.writeln('}')
+		if it.label.len > 0 {
+			g.writeln('\t$it.label\__break: {}')
+		}
 		g.writeln('/*for in map cleanup*/')
 		g.writeln('for (int $idx = 0; $idx < ${keys_tmp}.len; ++$idx) { string_free(&(($key_styp*)${keys_tmp}.data)[$idx]); }')
 		g.writeln('array_free(&$keys_tmp);')
+		return
 	} else if it.cond_type.has_flag(.variadic) {
 		g.writeln('// FOR IN cond_type/variadic')
 		i := if it.key_var in ['', '_'] { g.new_tmp_var() } else { it.key_var }
@@ -1215,8 +1245,6 @@ fn (mut g Gen) for_in(it ast.ForInStmt) {
 		g.write('\t$styp ${c_name(it.val_var)} = ')
 		g.expr(it.cond)
 		g.writeln('.args[$i];')
-		g.stmts(it.stmts)
-		g.writeln('}')
 	} else if it.kind == .string {
 		i := if it.key_var in ['', '_'] { g.new_tmp_var() } else { it.key_var }
 		g.write('for (int $i = 0; $i < ')
@@ -1227,12 +1255,18 @@ fn (mut g Gen) for_in(it ast.ForInStmt) {
 			g.expr(it.cond)
 			g.writeln('.str[$i];')
 		}
-		g.stmts(it.stmts)
-		g.writeln('}')
 	} else {
 		s := g.table.type_to_str(it.cond_type)
 		g.error('for in: unhandled symbol `$it.cond` of type `$s`', it.pos)
 	}
+	g.stmts(it.stmts)
+	if it.label.len > 0 {
+		g.writeln('\t$it.label\__continue: {}')
+	}
+	g.writeln('}')
+	if it.label.len > 0 {
+		g.writeln('\t$it.label\__break: {}')
+	}
 }
 
 // use instead of expr() when you need to cast to union sum type (can add other casts also)

vlib/v/parser/parser.v

@@ -594,6 +594,26 @@ pub fn (mut p Parser) stmt(is_top_level bool) ast.Stmt {
 					spos := p.tok.position()
 					name := p.check_name()
 					p.next()
+					if p.tok.kind == .key_for {
+						mut stmt := p.stmt(is_top_level)
+						match mut stmt {
+							ast.ForStmt {
+								stmt.label = name
+								return *stmt
+							}
+							ast.ForInStmt {
+								stmt.label = name
+								return *stmt
+							}
+							ast.ForCStmt {
+								stmt.label = name
+								return *stmt
+							}
+							else {
+								assert false
+							}
+						}
+					}
 					return ast.GotoLabel{
 						name: name
 						pos: spos.extend(p.tok.position())
@@ -630,9 +650,15 @@ pub fn (mut p Parser) stmt(is_top_level bool) ast.Stmt {
 		}
 		.key_continue, .key_break {
 			tok := p.tok
+			line := p.tok.line_nr
 			p.next()
+			mut label := ''
+			if p.tok.line_nr == line && p.tok.kind == .name {
+				label = p.check_name()
+			}
 			return ast.BranchStmt{
 				kind: tok.kind
+				label: label
 				pos: tok.position()
 			}
 		}

vlib/v/tests/named_break_continue_test.v

@@ -0,0 +1,31 @@
+fn test_labelled_for() {
+	mut i := 4
+	goto L1
+	L1: for {
+		i++
+		for {
+			if i < 7 {continue L1}
+			else {break L1}
+		}
+	}
+	assert i == 7
+
+	goto L2
+	L2: for ;; i++ {
+		for {
+			if i < 17 {continue L2}
+			else {break L2}
+		}
+	}
+	assert i == 17
+
+	goto L3
+	L3: for e in [1,2,3,4] {
+		i = e
+		for {
+			if i < 3 {continue L3}
+			else {break L3}
+		}
+	}
+	assert i == 3
+}