parser: prepare for better VLS integration, more accurate parser errors (#7119)

cmd/tools/check-md.v

@@ -191,14 +191,12 @@ fn (mut f MDFile) check_examples() (int, int) {
 		mut should_cleanup_vfile := true
 		// eprintln('>>> checking example $vfile ...')
 		vcontent := e.text.join('\n')
-		os.write_file(vfile, vcontent) or {
+		os.write_file(vfile, vcontent) or { panic(err) }
-			panic(err)
-		}
 		mut acommands := e.command.split(' ')
 		for command in acommands {
 			match command {
 				'compile' {
-					res := os.system('"$vexe" -silent -o x.c $vfile')
+					res := os.system('"$vexe" -w -Wfatal-errors -o x.c $vfile')
 					os.rm('x.c') or { }
 					if res != 0 {
 						eprintln(eline(f.path, e.sline, 0, 'example failed to compile'))
@@ -210,7 +208,7 @@ fn (mut f MDFile) check_examples() (int, int) {
 					oks++
 				}
 				'live' {
-					res := os.system('"$vexe" -silent -live -o x.c $vfile')
+					res := os.system('"$vexe" -w -Wfatal-errors -live -o x.c $vfile')
 					if res != 0 {
 						eprintln(eline(f.path, e.sline, 0, 'example failed to compile with -live'))
 						eprintln(vcontent)
@@ -221,7 +219,7 @@ fn (mut f MDFile) check_examples() (int, int) {
 					oks++
 				}
 				'failcompile' {
-					res := os.system('"$vexe" -silent -o x.c $vfile')
+					res := os.system('"$vexe" -w -Wfatal-errors -o x.c $vfile')
 					os.rm('x.c') or { }
 					if res == 0 {
 						eprintln(eline(f.path, e.sline, 0, '`failcompile` example compiled'))
@@ -233,7 +231,7 @@ fn (mut f MDFile) check_examples() (int, int) {
 					oks++
 				}
 				'oksyntax' {
-					res := os.system('"$vexe" -silent -check-syntax $vfile')
+					res := os.system('"$vexe" -w -Wfatal-errors -check-syntax $vfile')
 					if res != 0 {
 						eprintln(eline(f.path, e.sline, 0, '`oksyntax` example with invalid syntax'))
 						eprintln(vcontent)
@@ -244,7 +242,7 @@ fn (mut f MDFile) check_examples() (int, int) {
 					oks++
 				}
 				'badsyntax' {
-					res := os.system('"$vexe" -silent -check-syntax $vfile')
+					res := os.system('"$vexe" -w -Wfatal-errors -check-syntax $vfile')
 					if res == 0 {
 						eprintln(eline(f.path, e.sline, 0, '`badsyntax` example can be parsed fine'))
 						eprintln(vcontent)
@@ -262,9 +260,7 @@ fn (mut f MDFile) check_examples() (int, int) {
 			}
 		}
 		if should_cleanup_vfile {
-			os.rm(vfile) or {
+			os.rm(vfile) or { panic(err) }
-				panic(err)
-			}
 		}
 	}
 	return errors, oks

cmd/v/help/build.txt

@@ -125,6 +125,9 @@ The build flags are shared by the build and run commands:
    -W
       Treat all warnings as errors, even in development builds.
    
+   -Wfatal-errors
+      Unconditionally exit with exit(1) after the first error. Useful for scripts/tooling that calls V.
+
 For C-specific build flags, use `v help build-c`.
 
 See also:

doc/docs.md

@@ -297,8 +297,7 @@ In development mode the compiler will warn you that you haven't used the variabl
 In production mode (enabled by passing the `-prod` flag to v – `v -prod foo.v`)
 it will not compile at all (like in Go).
 
-<!-- this should be `failcompile`, but it compiles -->
+```v failcompile
-```v
 fn main() {
     a := 10
     if true {
@@ -1736,9 +1735,9 @@ color = .green
 println(color) // "green"
 
 match color {
-    .red { ... }
+    .red { println('the color was red') }
-    .green { ... }
+    .green { println('the color was green') }
-    .blue { ... }
+    .blue { println('the color was blue') }
 }
 
 ```

vlib/v/checker/checker.v

@@ -4391,6 +4391,9 @@ fn (mut c Checker) warn_or_error(message string, pos token.Position, warn bool)
 		return
 	}
 	if !warn {
+		if c.pref.fatal_errors {
+			exit(1)
+		}
 		c.nr_errors++
 		if pos.line_nr !in c.error_lines {
 			err := errors.Error{

vlib/v/parser/assign.v

@@ -11,33 +11,34 @@ fn (mut p Parser) assign_stmt() ast.Stmt {
 	return p.partial_assign_stmt(exprs, comments)
 }
 
-fn (mut p Parser) check_undefined_variables(exprs []ast.Expr, val ast.Expr) {
+fn (mut p Parser) check_undefined_variables(exprs []ast.Expr, val ast.Expr) ? {
 	match val {
 		ast.Ident {
 			for expr in exprs {
 				if expr is ast.Ident {
 					if expr.name == val.name {
 						p.error_with_pos('undefined variable: `$val.name`', val.pos)
+						return error('undefined variable: `$val.name`')
 					}
 				}
 			}
 		}
 		ast.InfixExpr {
-			p.check_undefined_variables(exprs, val.left)
+			p.check_undefined_variables(exprs, val.left) ?
-			p.check_undefined_variables(exprs, val.right)
+			p.check_undefined_variables(exprs, val.right) ?
 		}
 		ast.ParExpr {
-			p.check_undefined_variables(exprs, val.expr)
+			p.check_undefined_variables(exprs, val.expr) ?
 		}
 		ast.PostfixExpr {
-			p.check_undefined_variables(exprs, val.expr)
+			p.check_undefined_variables(exprs, val.expr) ?
 		}
 		ast.PrefixExpr {
-			p.check_undefined_variables(exprs, val.right)
+			p.check_undefined_variables(exprs, val.right) ?
 		}
 		ast.StringInterLiteral {
 			for expr_ in val.exprs {
-				p.check_undefined_variables(exprs, expr_)
+				p.check_undefined_variables(exprs, expr_) ?
 			}
 		}
 		else {}
@@ -105,6 +106,7 @@ fn (mut p Parser) partial_assign_stmt(left []ast.Expr, left_comments []ast.Comme
 			has_cross_var = p.check_cross_variables(left, r)
 			if op !in [.assign, .decl_assign] {
 				p.error('unexpected $op.str(), expecting := or = or comma')
+				return ast.Stmt{}
 			}
 			if has_cross_var {
 				break
@@ -118,6 +120,7 @@ fn (mut p Parser) partial_assign_stmt(left []ast.Expr, left_comments []ast.Comme
 				if op == .decl_assign {
 					if p.scope.known_var(lx.name) {
 						p.error_with_pos('redefinition of `$lx.name`', lx.pos)
+						return ast.Stmt{}
 					}
 					mut share := table.ShareType(0)
 					if lx.info is ast.IdentVar {
@@ -127,6 +130,7 @@ fn (mut p Parser) partial_assign_stmt(left []ast.Expr, left_comments []ast.Comme
 							if !p.pref.translated {
 								p.error_with_pos('static variables are supported only in -translated mode',
 									lx.pos)
+								return ast.Stmt{}
 							}
 							is_static = true
 						}
@@ -159,6 +163,7 @@ fn (mut p Parser) partial_assign_stmt(left []ast.Expr, left_comments []ast.Comme
 				if op == .decl_assign {
 					p.error_with_pos('non-name `$lx.left[$lx.index]` on left side of `:=`',
 						lx.pos)
+					return ast.Stmt{}
 				}
 				lx.is_setter = true
 			}
@@ -168,6 +173,7 @@ fn (mut p Parser) partial_assign_stmt(left []ast.Expr, left_comments []ast.Comme
 				if op == .decl_assign {
 					p.error_with_pos('struct fields can only be declared during the initialization',
 						lx.pos)
+					return ast.Stmt{}
 				}
 			}
 			else {

vlib/v/parser/comptime.v

@@ -51,12 +51,14 @@ fn (mut p Parser) vweb() ast.ComptimeCall {
 		n := p.check_name() // skip `vweb.html()` TODO
 		if n != 'vweb' {
 			p.error(error_msg)
+			return ast.ComptimeCall{}
 		}
 		p.check(.dot)
 	}
 	n := p.check_name() // (.name)
 	if n != 'html' && n != 'tmpl' {
 		p.error(error_msg)
+		return ast.ComptimeCall{}
 	}
 	is_html := n == 'html'
 	p.check(.lpar)
@@ -85,8 +87,10 @@ fn (mut p Parser) vweb() ast.ComptimeCall {
 		if !os.exists(path) {
 			if is_html {
 				p.error('vweb HTML template "$path" not found')
+				return ast.ComptimeCall{}
 			} else {
 				p.error('template file "$path" not found')
+				return ast.ComptimeCall{}
 			}
 		}
 		// println('path is now "$path"')
@@ -171,6 +175,7 @@ fn (mut p Parser) comp_for() ast.CompFor {
 		kind = .fields
 	} else {
 		p.error('unknown kind `$for_val`, available are: `methods` or `fields`')
+		return ast.CompFor{}
 	}
 	spos := p.tok.position()
 	stmts := p.parse_block()

vlib/v/parser/containers.v

@@ -65,6 +65,7 @@ fn (mut p Parser) array_init() ast.ArrayInit {
 					n := p.check_name()
 					if n != 'init' {
 						p.error_with_pos('expected `init:`, not `$n`', pos)
+						return ast.ArrayInit{}
 					}
 					p.check(.colon)
 					has_default = true
@@ -117,6 +118,7 @@ fn (mut p Parser) array_init() ast.ArrayInit {
 				}
 				else {
 					p.error('wrong field `$key`, expecting `len`, `cap`, or `init`')
+					return ast.ArrayInit{}
 				}
 			}
 			if p.tok.kind != .rcbr {

vlib/v/parser/fn.v

@@ -111,7 +111,7 @@ pub fn (mut p Parser) call_args() []ast.CallArg {
 	for p.tok.kind != .rpar {
 		if p.tok.kind == .eof {
 			p.error_with_pos('unexpected eof reached, while parsing call argument', start_pos)
-			break
+			return []
 		}
 		is_shared := p.tok.kind == .key_shared
 		is_atomic := p.tok.kind == .key_atomic
@@ -197,6 +197,7 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 		rec_type = p.parse_type_with_mut(rec_mut)
 		if is_amp && rec_mut {
 			p.error('use `(mut f Foo)` or `(f &Foo)` instead of `(mut f &Foo)`')
+			return ast.FnDecl{}
 		}
 		if is_shared {
 			rec_type = rec_type.set_flag(.shared_f)
@@ -220,11 +221,13 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 		name = if language == .js { p.check_js_name() } else { p.check_name() }
 		if language == .v && !p.pref.translated && util.contains_capital(name) {
 			p.error('function names cannot contain uppercase letters, use snake_case instead')
+			return ast.FnDecl{}
 		}
 		type_sym := p.table.get_type_symbol(rec_type)
 		// interfaces are handled in the checker, methods can not be defined on them this way
 		if is_method && (type_sym.has_method(name) && type_sym.kind != .interface_) {
 			p.error('duplicate method `$name`')
+			return ast.FnDecl{}
 		}
 	}
 	if p.tok.kind in [.plus, .minus, .mul, .div, .mod] {
@@ -245,7 +248,7 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 		for param in params {
 			if p.scope.known_var(param.name) {
 				p.error_with_pos('redefinition of parameter `$param.name`', param.pos)
-				break
+				return ast.FnDecl{}
 			}
 			p.scope.register(ast.Var{
 				name: param.name
@@ -274,6 +277,7 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 		// we could also check if kind is .array,  .array_fixed, .map instead of mod.len
 		if type_sym.mod.len > 0 && type_sym.mod != p.mod && type_sym.language == .v {
 			p.error('cannot define new methods on non-local type $type_sym.name')
+			return ast.FnDecl{}
 		}
 		// p.warn('reg method $type_sym.name . $name ()')
 		type_sym_method_idx = type_sym.register_method(table.Fn{
@@ -329,6 +333,7 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 	p.close_scope()
 	if !no_body && are_args_type_only {
 		p.error_with_pos('functions with type only args can not have bodies', body_start_pos)
+		return ast.FnDecl{}
 	}
 	return ast.FnDecl{
 		name: name
@@ -452,7 +457,7 @@ fn (mut p Parser) fn_args() ([]table.Param, bool, bool) {
 					}
 				} else if is_shared || is_atomic {
 					p.error_with_pos('generic object cannot be `atomic`or `shared`', pos)
-					break
+					return []table.Param{}, false, false
 				}
 				// if arg_type.is_ptr() {
 				// p.error('cannot mut')
@@ -473,7 +478,7 @@ fn (mut p Parser) fn_args() ([]table.Param, bool, bool) {
 				if is_variadic {
 					p.error_with_pos('cannot use ...(variadic) with non-final parameter no $arg_no',
 						pos)
-					break
+					return []table.Param{}, false, false
 				}
 				p.next()
 			}
@@ -488,7 +493,7 @@ fn (mut p Parser) fn_args() ([]table.Param, bool, bool) {
 			arg_no++
 			if arg_no > 1024 {
 				p.error_with_pos('too many args', pos)
-				break
+				return []table.Param{}, false, false
 			}
 		}
 	} else {
@@ -534,7 +539,7 @@ fn (mut p Parser) fn_args() ([]table.Param, bool, bool) {
 				} else if is_shared || is_atomic {
 					p.error_with_pos('generic object cannot be `atomic` or `shared`',
 						pos)
-					break
+					return []table.Param{}, false, false
 				}
 				typ = typ.set_nr_muls(1)
 				if is_shared {
@@ -560,7 +565,7 @@ fn (mut p Parser) fn_args() ([]table.Param, bool, bool) {
 				if is_variadic && p.tok.kind == .comma {
 					p.error_with_pos('cannot use ...(variadic) with non-final parameter $arg_name',
 						arg_pos[i])
-					break
+					return []table.Param{}, false, false
 				}
 			}
 			if p.tok.kind != .rpar {

vlib/v/parser/for.v

@@ -13,6 +13,7 @@ fn (mut p Parser) for_stmt() ast.Stmt {
 	p.inside_for = true
 	if p.tok.kind == .key_match {
 		p.error('cannot use `match` in `for` loop')
+		return ast.Stmt{}
 	}
 	// defer { p.close_scope() }
 	// Infinite loop
@@ -29,6 +30,7 @@ fn (mut p Parser) for_stmt() ast.Stmt {
 		// `for i := 0; i < 10; i++ {`
 		if p.tok.kind == .key_mut {
 			p.error('`mut` is not needed in `for ;;` loops: use `for i := 0; i < n; i ++ {`')
+			return ast.Stmt{}
 		}
 		mut init := ast.Stmt{}
 		mut cond := p.new_true_expr()
@@ -47,6 +49,7 @@ fn (mut p Parser) for_stmt() ast.Stmt {
 			// Disallow `for i := 0; i++; i < ...`
 			if p.tok.kind == .name && p.peek_tok.kind in [.inc, .dec] {
 				p.error('cannot use $p.tok.lit$p.peek_tok.kind as value')
+				return ast.Stmt{}
 			}
 			cond = p.expr(0)
 			has_cond = true
@@ -87,12 +90,15 @@ fn (mut p Parser) for_stmt() ast.Stmt {
 			val_var_name = p.check_name()
 			if key_var_name == val_var_name && key_var_name != '_' {
 				p.error_with_pos('key and value in a for loop cannot be the same', val_var_pos)
+				return ast.Stmt{}
 			}
 			if p.scope.known_var(key_var_name) {
 				p.error('redefinition of key iteration variable `$key_var_name`')
+				return ast.Stmt{}
 			}
 			if p.scope.known_var(val_var_name) {
 				p.error('redefinition of value iteration variable `$val_var_name`')
+				return ast.Stmt{}
 			}
 			p.scope.register(ast.Var{
 				name: key_var_name
@@ -101,10 +107,12 @@ fn (mut p Parser) for_stmt() ast.Stmt {
 			})
 		} else if p.scope.known_var(val_var_name) {
 			p.error('redefinition of value iteration variable `$val_var_name`')
+			return ast.Stmt{}
 		}
 		p.check(.key_in)
 		if p.tok.kind == .name && p.tok.lit in [key_var_name, val_var_name] {
 			p.error('in a `for x in array` loop, the key or value iteration variable `$p.tok.lit` can not be the same as the array variable')
+			return ast.Stmt{}
 		}
 		// arr_expr
 		cond := p.expr(0)
@@ -124,6 +132,7 @@ fn (mut p Parser) for_stmt() ast.Stmt {
 			})
 			if key_var_name.len > 0 {
 				p.error_with_pos('cannot declare index variable with range `for`', key_var_pos)
+				return ast.Stmt{}
 			}
 		} else {
 			// this type will be set in checker

vlib/v/parser/if_match.v

@@ -35,6 +35,7 @@ fn (mut p Parser) if_expr(is_comptime bool) ast.IfExpr {
 			comments << p.eat_comments()
 			if p.tok.kind == .key_match {
 				p.error('cannot use `match` with `if` statements')
+				return ast.IfExpr{}
 			}
 			if p.tok.kind == .lcbr {
 				// else {
@@ -82,6 +83,7 @@ fn (mut p Parser) if_expr(is_comptime bool) ast.IfExpr {
 		p.check(.key_if)
 		if p.tok.kind == .key_match {
 			p.error('cannot use `match` with `if` statements')
+			return ast.IfExpr{}
 		}
 		comments << p.eat_comments()
 		mut cond := ast.Expr{}
@@ -129,6 +131,7 @@ fn (mut p Parser) if_expr(is_comptime bool) ast.IfExpr {
 		if is_comptime {
 			if p.tok.kind == .key_else {
 				p.error('use `\$else` instead of `else` in compile-time `if` branches')
+				return ast.IfExpr{}
 			}
 			if p.peek_tok.kind == .key_else {
 				p.check(.dollar)
@@ -199,6 +202,7 @@ fn (mut p Parser) match_expr() ast.MatchExpr {
 				if p.tok.kind == .dotdot {
 					p.error_with_pos('match only supports inclusive (`...`) ranges, not exclusive (`..`)',
 						p.tok.position())
+					return ast.MatchExpr{}
 				} else if p.tok.kind == .ellipsis {
 					p.next()
 					expr2 := p.expr(0)
@@ -283,10 +287,12 @@ fn (mut p Parser) select_expr() ast.SelectExpr {
 			if has_timeout {
 				p.error_with_pos('timeout `> t` and `else` are mutually exclusive `select` keys',
 					p.tok.position())
+				return ast.SelectExpr{}
 			}
 			if has_else {
 				p.error_with_pos('at most one `else` branch allowed in `select` block',
 					p.tok.position())
+				return ast.SelectExpr{}
 			}
 			is_else = true
 			has_else = true
@@ -295,10 +301,12 @@ fn (mut p Parser) select_expr() ast.SelectExpr {
 			if has_else {
 				p.error_with_pos('`else` and timeout `> t` are mutually exclusive `select` keys',
 					p.tok.position())
+				return ast.SelectExpr{}
 			}
 			if has_timeout {
 				p.error_with_pos('at most one timeout `> t` branch allowed in `select` block',
 					p.tok.position())
+				return ast.SelectExpr{}
 			}
 			is_timeout = true
 			has_timeout = true
@@ -318,6 +326,7 @@ fn (mut p Parser) select_expr() ast.SelectExpr {
 			exprs, comments := p.expr_list()
 			if exprs.len != 1 {
 				p.error('only one expression allowed as `select` key')
+				return ast.SelectExpr{}
 			}
 			if p.tok.kind in [.assign, .decl_assign] {
 				stmt = p.partial_assign_stmt(exprs, comments)
@@ -335,17 +344,20 @@ fn (mut p Parser) select_expr() ast.SelectExpr {
 				ast.ExprStmt {
 					if !stmt.is_expr {
 						p.error_with_pos('select: invalid expression', stmt.pos)
+						return ast.SelectExpr{}
 					} else {
 						match mut stmt.expr {
 							ast.InfixExpr {
 								if stmt.expr.op != .arrow {
 									p.error_with_pos('select key: `<-` operator expected',
 										stmt.expr.pos)
+									return ast.SelectExpr{}
 								}
 							}
 							else {
 								p.error_with_pos('select key: send expression (`ch <- x`) expected',
 									stmt.pos)
+								return ast.SelectExpr{}
 							}
 						}
 					}
@@ -357,16 +369,19 @@ fn (mut p Parser) select_expr() ast.SelectExpr {
 							if expr.op != .arrow {
 								p.error_with_pos('select key: `<-` operator expected',
 									expr.pos)
+								return ast.SelectExpr{}
 							}
 						}
 						else {
 							p.error_with_pos('select key: receive expression expected',
 								stmt.right[0].position())
+							return ast.SelectExpr{}
 						}
 					}
 				}
 				else {
 					p.error_with_pos('select: transmission statement expected', stmt.position())
+					return ast.SelectExpr{}
 				}
 			}
 		}

vlib/v/parser/parse_type.v

@@ -44,6 +44,7 @@ pub fn (mut p Parser) parse_map_type() table.Type {
 	// if key_type_sym.kind != .string {
 	if key_type.idx() != table.string_type_idx {
 		p.error('maps can only have string keys for now')
+		return 0
 	}
 	p.check(.rsbr)
 	value_type := p.parse_type()
@@ -151,6 +152,7 @@ pub fn (mut p Parser) parse_type() table.Type {
 	}
 	if p.tok.kind == .mul {
 		p.error('use `&Type` instead of `*Type` when declaring references')
+		return 0
 	}
 	mut nr_amps := 0
 	// &Type
@@ -167,6 +169,7 @@ pub fn (mut p Parser) parse_type() table.Type {
 		typ = p.parse_any_type(language, nr_muls > 0, true)
 		if typ == table.void_type {
 			p.error_with_pos('use `?` instead of `?void`', pos)
+			return 0
 		}
 	}
 	if is_optional {
@@ -184,6 +187,7 @@ pub fn (mut p Parser) parse_type() table.Type {
 			p.error('V arrays are already references behind the scenes,
 there is no need to use a reference to an array (e.g. use `[]string` instead of `&[]string`).
 If you need to modify an array in a function, use a mutable argument instead: `fn foo(mut s []string) {}`.')
+			return 0
 		}
 	}
 	return typ
@@ -200,6 +204,7 @@ pub fn (mut p Parser) parse_any_type(language table.Language, is_ptr bool, check
 		// /if !(p.tok.lit in p.table.imports) {
 		if !p.known_import(name) {
 			p.error('unknown module `$p.tok.lit`')
+			return 0
 		}
 		if p.tok.lit in p.imports {
 			p.register_used_import(p.tok.lit)
@@ -210,6 +215,7 @@ pub fn (mut p Parser) parse_any_type(language table.Language, is_ptr bool, check
 		name = '${p.imports[name]}.$p.tok.lit'
 		if !p.tok.lit[0].is_capital() {
 			p.error('imported types must start with a capital letter')
+			return 0
 		}
 	} else if p.expr_mod != '' && !p.in_generic_params { // p.expr_mod is from the struct and not from the generic parameter
 		name = p.expr_mod + '.' + name
@@ -231,6 +237,7 @@ pub fn (mut p Parser) parse_any_type(language table.Language, is_ptr bool, check
 			// multiple return
 			if is_ptr {
 				p.error('parse_type: unexpected `&` before multiple returns')
+				return 0
 			}
 			return p.parse_multi_return_type()
 		}
@@ -248,6 +255,7 @@ pub fn (mut p Parser) parse_any_type(language table.Language, is_ptr bool, check
 			if name == '' {
 				// This means the developer is using some wrong syntax like `x: int` instead of `x int`
 				p.error('bad type syntax')
+				return 0
 			}
 			match name {
 				'voidptr' {

vlib/v/parser/parser.v

@@ -359,6 +359,7 @@ pub fn (mut p Parser) parse_block_no_scope(is_top_level bool) []ast.Stmt {
 			if c > 1000000 {
 				p.error_with_pos('parsed over $c statements from fn $p.cur_fn_name, the parser is probably stuck',
 					p.tok.position())
+				return []
 			}
 		}
 	}
@@ -396,8 +397,10 @@ fn (mut p Parser) check(expected token.Kind) {
 	if p.tok.kind != expected {
 		if p.tok.kind == .name {
 			p.error('unexpected name `$p.tok.lit`, expecting `$expected.str()`')
+			return
 		} else {
 			p.error('unexpected `$p.tok.kind.str()`, expecting `$expected.str()`')
+			return
 		}
 	}
 	p.next()
@@ -645,9 +648,11 @@ pub fn (mut p Parser) stmt(is_top_level bool) ast.Stmt {
 					}
 				} else if p.peek_tok.kind == .name {
 					p.error_with_pos('unexpected name `$p.peek_tok.lit`', p.peek_tok.position())
+					return ast.Stmt{}
 				} else if !p.inside_if_expr && !p.inside_match_body && !p.inside_or_expr &&
 					p.peek_tok.kind in [.rcbr, .eof] && !p.mark_var_as_used(p.tok.lit) {
 					p.error_with_pos('`$p.tok.lit` evaluated but not used', p.tok.position())
+					return ast.Stmt{}
 				}
 			}
 			return p.parse_multi_expr(is_top_level)
@@ -761,11 +766,13 @@ fn (mut p Parser) attributes() {
 		attr := p.parse_attr()
 		if p.attrs.contains(attr.name) {
 			p.error_with_pos('duplicate attribute `$attr.name`', start_pos.extend(p.prev_tok.position()))
+			return
 		}
 		if attr.is_ctdefine {
 			if has_ctdefine {
 				p.error_with_pos('only one `[if flag]` may be applied at a time `$attr.name`',
 					start_pos.extend(p.prev_tok.position()))
+				return
 			} else {
 				has_ctdefine = true
 			}
@@ -777,11 +784,13 @@ fn (mut p Parser) attributes() {
 				break
 			}
 			p.error('unexpected `$p.tok.kind.str()`, expecting `;`')
+			return
 		}
 		p.next()
 	}
 	if p.attrs.len == 0 {
 		p.error_with_pos('attributes cannot be empty', p.prev_tok.position().extend(p.tok.position()))
+		return
 	}
 }
 
@@ -808,8 +817,10 @@ fn (mut p Parser) parse_attr() table.Attr {
 		name = p.check_name()
 		if name == 'unsafe_fn' {
 			p.error_with_pos('please use `[unsafe]` instead', p.tok.position())
+			return table.Attr{}
 		} else if name == 'trusted_fn' {
 			p.error_with_pos('please use `[trusted]` instead', p.tok.position())
+			return table.Attr{}
 		}
 		if p.tok.kind == .colon {
 			p.next()
@@ -841,6 +852,9 @@ pub fn (mut p Parser) warn(s string) {
 }
 
 pub fn (mut p Parser) error_with_pos(s string, pos token.Position) {
+	if p.pref.fatal_errors {
+		exit(1)
+	}
 	mut kind := 'error:'
 	if p.pref.output_mode == .stdout {
 		if p.pref.is_verbose {
@@ -902,6 +916,7 @@ fn (mut p Parser) parse_multi_expr(is_top_level bool) ast.Stmt {
 	left0 := left[0]
 	if tok.kind == .key_mut && p.tok.kind != .decl_assign {
 		p.error('expecting `:=` (e.g. `mut x :=`)')
+		return ast.Stmt{}
 	}
 	if p.tok.kind in [.assign, .decl_assign] || p.tok.kind.is_assign() {
 		return p.partial_assign_stmt(left, left_comments)
@@ -910,6 +925,7 @@ fn (mut p Parser) parse_multi_expr(is_top_level bool) ast.Stmt {
 		!(left0 is ast.InfixExpr && (left0 as ast.InfixExpr).op in [.left_shift, .arrow]) && left0 !is
 		ast.ComptimeCall {
 		p.error_with_pos('expression evaluated but not used', left0.position())
+		return ast.Stmt{}
 	}
 	if left.len == 1 {
 		return ast.ExprStmt{
@@ -980,6 +996,7 @@ pub fn (mut p Parser) parse_ident(language table.Language) ast.Ident {
 		}
 	} else {
 		p.error('unexpected token `$p.tok.lit`')
+		return ast.Ident{}
 	}
 	return ast.Ident{}
 }
@@ -1040,9 +1057,11 @@ pub fn (mut p Parser) name_expr() ast.Expr {
 				}
 				'len', 'init' {
 					p.error('`$key` cannot be initialized for `chan`. Did you mean `cap`?')
+					return ast.Expr{}
 				}
 				else {
 					p.error('wrong field `$key`, expecting `cap`')
+					return ast.Expr{}
 				}
 			}
 			last_pos = p.tok.position()
@@ -1062,12 +1081,14 @@ pub fn (mut p Parser) name_expr() ast.Expr {
 		} else {
 			// don't allow any other string prefix except `r`, `js` and `c`
 			p.error('only `c`, `r`, `js` are recognized string prefixes, but you tried to use `$p.tok.lit`')
+			return ast.Expr{}
 		}
 	}
 	// don't allow r`byte` and c`byte`
 	if p.tok.lit in ['r', 'c'] && p.peek_tok.kind == .chartoken {
 		opt := if p.tok.lit == 'r' { '`r` (raw string)' } else { '`c` (c string)' }
 		p.error('cannot use $opt with `byte` and `rune`')
+		return ast.Expr{}
 	}
 	known_var := p.mark_var_as_used(p.tok.lit)
 	mut is_mod_cast := false
@@ -1321,6 +1342,7 @@ fn (mut p Parser) dot_expr(left ast.Expr) ast.Expr {
 		args := p.call_args()
 		if is_filter && args.len != 1 {
 			p.error('needs exactly 1 argument')
+			return ast.Expr{}
 		}
 		p.check(.rpar)
 		mut or_stmts := []ast.Stmt{}
@@ -1486,6 +1508,7 @@ fn (mut p Parser) string_expr() ast.Expr {
 					p.next()
 				} else {
 					p.error('format specifier may only be one letter')
+					return ast.Expr{}
 				}
 			}
 		}
@@ -1544,13 +1567,16 @@ fn (mut p Parser) module_decl() ast.Module {
 		name = p.check_name()
 		if module_pos.line_nr != pos.line_nr {
 			p.error_with_pos('`module` and `$name` must be at same line', pos)
+			return ast.Module{}
 		}
 		pos = p.tok.position()
 		if module_pos.line_nr == pos.line_nr && p.tok.kind != .comment {
 			if p.tok.kind != .name {
 				p.error_with_pos('`module x` syntax error', pos)
+				return ast.Module{}
 			} else {
 				p.error_with_pos('`module x` can only declare one module', pos)
+				return ast.Module{}
 			}
 		}
 		module_pos = module_pos.extend(pos)
@@ -1584,10 +1610,12 @@ fn (mut p Parser) import_stmt() ast.Import {
 	pos := p.tok.position()
 	if p.tok.kind == .lpar {
 		p.error_with_pos('`import()` has been deprecated, use `import x` instead', pos)
+		return ast.Import{}
 	}
 	mut mod_name := p.check_name()
 	if import_pos.line_nr != pos.line_nr {
 		p.error_with_pos('`import` statements must be a single line', pos)
+		return ast.Import{}
 	}
 	mut mod_alias := mod_name
 	for p.tok.kind == .dot {
@@ -1595,9 +1623,11 @@ fn (mut p Parser) import_stmt() ast.Import {
 		pos_t := p.tok.position()
 		if p.tok.kind != .name {
 			p.error_with_pos('module syntax error, please use `x.y.z`', pos)
+			return ast.Import{}
 		}
 		if import_pos.line_nr != pos_t.line_nr {
 			p.error_with_pos('`import` and `submodule` must be at same line', pos)
+			return ast.Import{}
 		}
 		submod_name := p.check_name()
 		mod_name += '.' + submod_name
@@ -1608,6 +1638,7 @@ fn (mut p Parser) import_stmt() ast.Import {
 		mod_alias = p.check_name()
 		if mod_alias == mod_name.split('.').last() {
 			p.error_with_pos('import alias `$mod_name as $mod_alias` is redundant', p.prev_tok.position())
+			return ast.Import{}
 		}
 	}
 	mut node := ast.Import{
@@ -1623,6 +1654,7 @@ fn (mut p Parser) import_stmt() ast.Import {
 	if import_pos.line_nr == pos_t.line_nr {
 		if p.tok.kind !in [.lcbr, .eof, .comment] {
 			p.error_with_pos('cannot import multiple modules at a time', pos_t)
+			return ast.Import{}
 		}
 	}
 	p.imports[mod_alias] = mod_name
@@ -1639,10 +1671,12 @@ fn (mut p Parser) import_syms(mut parent ast.Import) {
 	pos_t := p.tok.position()
 	if p.tok.kind == .rcbr { // closed too early
 		p.error_with_pos('empty `$parent.mod` import set, remove `{}`', pos_t)
+		return
 	}
 	if p.tok.kind != .name { // not a valid inner name
 		p.error_with_pos('import syntax error, please specify a valid fn or type name',
 			pos_t)
+		return
 	}
 	for p.tok.kind == .name {
 		pos := p.tok.position()
@@ -1697,6 +1731,7 @@ fn (mut p Parser) import_syms(mut parent ast.Import) {
 	}
 	if p.tok.kind != .rcbr {
 		p.error_with_pos('import syntax error, no closing `}`', p.tok.position())
+		return
 	}
 	p.next()
 }
@@ -1739,6 +1774,7 @@ fn (mut p Parser) const_decl() ast.ConstDecl {
 		p.check(.assign)
 		if p.tok.kind == .key_fn {
 			p.error('const initializer fn literal is not a constant')
+			return ast.ConstDecl{}
 		}
 		expr := p.expr(0)
 		field := ast.ConstField{
@@ -1795,12 +1831,14 @@ fn (mut p Parser) global_decl() ast.GlobalDecl {
 		p.mod != 'ui' && p.mod != 'gg2' && p.mod != 'uiold' && !p.pref.enable_globals && !p.pref.is_fmt &&
 		p.mod !in global_enabled_mods {
 		p.error('use `v --enable-globals ...` to enable globals')
+		return ast.GlobalDecl{}
 	}
 	start_pos := p.tok.position()
 	end_pos := p.tok.position()
 	p.check(.key_global)
 	if p.tok.kind != .lpar {
 		p.error('globals must be grouped, e.g. `__global ( a = int(1) )`')
+		return ast.GlobalDecl{}
 	}
 	p.next() // (
 	mut fields := []ast.GlobalField{}
@@ -1819,11 +1857,13 @@ fn (mut p Parser) global_decl() ast.GlobalDecl {
 		typ := p.parse_type()
 		if p.tok.kind == .assign {
 			p.error('global assign must have the type around the value, use `__global ( name = type(value) )`')
+			return ast.GlobalDecl{}
 		}
 		mut expr := ast.Expr{}
 		if has_expr {
 			if p.tok.kind != .lpar {
 				p.error('global assign must have a type and value, use `__global ( name = type(value) )` or `__global ( name type )`')
+				return ast.GlobalDecl{}
 			}
 			p.next() // (
 			expr = p.expr(0)
@@ -1862,6 +1902,7 @@ fn (mut p Parser) enum_decl() ast.EnumDecl {
 	if enum_name.len == 1 {
 		p.error_with_pos('single letter capital names are reserved for generic template types.',
 			end_pos)
+		return ast.EnumDecl{}
 	}
 	name := p.prepend_mod(enum_name)
 	p.check(.lcbr)
@@ -1896,11 +1937,13 @@ fn (mut p Parser) enum_decl() ast.EnumDecl {
 	if is_flag {
 		if fields.len > 32 {
 			p.error('when an enum is used as bit field, it must have a max of 32 fields')
+			return ast.EnumDecl{}
 		}
 		for f in fields {
 			if f.has_expr {
 				p.error_with_pos('when an enum is used as a bit field, you can not assign custom values',
 					f.pos)
+				return ast.EnumDecl{}
 			}
 		}
 		pubfn := if p.mod == 'main' { 'fn' } else { 'pub fn' }
@@ -1950,6 +1993,7 @@ fn (mut p Parser) type_decl() ast.TypeDecl {
 	if name.len == 1 && name[0].is_capital() {
 		p.error_with_pos('single letter capital names are reserved for generic template types.',
 			decl_pos)
+		return ast.TypeDecl{}
 	}
 	mut sum_variants := []ast.SumTypeVariant{}
 	p.check(.assign)
@@ -2155,10 +2199,12 @@ fn (mut p Parser) unsafe_stmt() ast.Stmt {
 	p.next()
 	if p.tok.kind != .lcbr {
 		p.error_with_pos('please use `unsafe {`', p.tok.position())
+		return ast.Stmt{}
 	}
 	p.next()
 	if p.inside_unsafe {
 		p.error_with_pos('already inside `unsafe` block', pos)
+		return ast.Stmt{}
 	}
 	if p.tok.kind == .rcbr {
 		// `unsafe {}`

vlib/v/parser/pratt.v

@@ -50,9 +50,16 @@ pub fn (mut p Parser) expr(precedence int) ast.Expr {
 		}
 		.dollar {
 			match p.peek_tok.kind {
-				.name { return p.vweb() }
+				.name {
-				.key_if { return p.if_expr(true) }
+					return p.vweb()
-				else { p.error_with_pos('unexpected `$`', p.peek_tok.position()) }
+				}
+				.key_if {
+					return p.if_expr(true)
+				}
+				else {
+					p.error_with_pos('unexpected `$`', p.peek_tok.position())
+					return ast.Expr{}
+				}
 			}
 		}
 		.chartoken {
@@ -100,6 +107,7 @@ pub fn (mut p Parser) expr(precedence int) ast.Expr {
 			p.next()
 			if p.inside_unsafe {
 				p.error_with_pos('already inside `unsafe` block', pos)
+				return ast.Expr{}
 			}
 			p.inside_unsafe = true
 			p.check(.lcbr)
@@ -193,9 +201,11 @@ pub fn (mut p Parser) expr(precedence int) ast.Expr {
 					p.next()
 					s := if p.tok.lit != '' { '`$p.tok.lit`' } else { p.tok.kind.str() }
 					p.error_with_pos('unexpected $s, expecting `:`', p.tok.position())
+					return ast.Expr{}
 				} else {
 					p.error_with_pos('unexpected `$p.tok.lit`, expecting struct key',
 						p.tok.position())
+					return ast.Expr{}
 				}
 			}
 			p.check(.rcbr)
@@ -235,6 +245,7 @@ pub fn (mut p Parser) expr(precedence int) ast.Expr {
 				// eof should be handled where it happens
 				p.error_with_pos('invalid expression: unexpected $p.tok.kind.str() token',
 					p.tok.position())
+				return ast.Expr{}
 			}
 		}
 	}

vlib/v/parser/sql.v

@@ -52,6 +52,7 @@ fn (mut p Parser) sql_expr() ast.Expr {
 			p.check_name() // `by`
 		} else {
 			p.error_with_pos('use `order by` in ORM queries', order_pos)
+			return ast.Expr{}
 		}
 		has_order = true
 		order_expr = p.expr(0)
@@ -139,6 +140,7 @@ fn (mut p Parser) sql_stmt() ast.SqlStmt {
 			}
 			else {
 				p.error('can only insert variables')
+				return ast.SqlStmt{}
 			}
 		}
 	}
@@ -147,9 +149,11 @@ fn (mut p Parser) sql_stmt() ast.SqlStmt {
 	mut update_exprs := []ast.Expr{cap: 5}
 	if kind == .insert && n != 'into' {
 		p.error('expecting `into`')
+		return ast.SqlStmt{}
 	} else if kind == .update {
 		if n != 'set' {
 			p.error('expecting `set`')
+			return ast.SqlStmt{}
 		}
 		for {
 			column := p.check_name()
@@ -164,6 +168,7 @@ fn (mut p Parser) sql_stmt() ast.SqlStmt {
 		}
 	} else if kind == .delete && n != 'from' {
 		p.error('expecting `from`')
+		return ast.SqlStmt{}
 	}
 	mut table_type := table.Type(0)
 	mut where_expr := ast.Expr{}
@@ -179,13 +184,13 @@ fn (mut p Parser) sql_stmt() ast.SqlStmt {
 			idx := p.table.find_type_idx(p.prepend_mod(table_name))
 			table_type = table.new_type(idx)
 		}
-		p.check_sql_keyword('where')
+		p.check_sql_keyword('where') or { return ast.SqlStmt{} }
 		where_expr = p.expr(0)
 	} else if kind == .delete {
 		table_type = p.parse_type()
 		sym := p.table.get_type_symbol(table_type)
 		table_name = sym.name
-		p.check_sql_keyword('where')
+		p.check_sql_keyword('where') or { return ast.SqlStmt{} }
 		where_expr = p.expr(0)
 	}
 	p.check(.rcbr)
@@ -202,8 +207,10 @@ fn (mut p Parser) sql_stmt() ast.SqlStmt {
 	}
 }
 
-fn (mut p Parser) check_sql_keyword(name string) {
+fn (mut p Parser) check_sql_keyword(name string) ?bool {
 	if p.check_name() != name {
 		p.error('orm: expecting `$name`')
+		return none
 	}
+	return true
 }

vlib/v/parser/struct.v

@@ -45,6 +45,7 @@ fn (mut p Parser) struct_decl() ast.StructDecl {
 	if name.len == 1 && name[0].is_capital() {
 		p.error_with_pos('single letter capital names are reserved for generic template types.',
 			name_pos)
+		return ast.StructDecl{}
 	}
 	mut generic_types := []table.Type{}
 	if p.tok.kind == .lt {
@@ -61,13 +62,16 @@ fn (mut p Parser) struct_decl() ast.StructDecl {
 	no_body := p.tok.kind != .lcbr
 	if language == .v && no_body {
 		p.error('`$p.tok.lit` lacks body')
+		return ast.StructDecl{}
 	}
 	if language == .v &&
 		p.mod != 'builtin' && name.len > 0 && !name[0].is_capital() && !p.pref.translated {
 		p.error_with_pos('struct name `$name` must begin with capital letter', name_pos)
+		return ast.StructDecl{}
 	}
 	if name.len == 1 {
 		p.error_with_pos('struct names must have more than one character', name_pos)
+		return ast.StructDecl{}
 	}
 	// println('struct decl $name')
 	mut ast_fields := []ast.StructField{}
@@ -100,6 +104,7 @@ fn (mut p Parser) struct_decl() ast.StructDecl {
 				if p.tok.kind == .key_mut {
 					if pub_mut_pos != -1 {
 						p.error('redefinition of `pub mut` section')
+						return ast.StructDecl{}
 					}
 					p.next()
 					pub_mut_pos = fields.len
@@ -109,6 +114,7 @@ fn (mut p Parser) struct_decl() ast.StructDecl {
 				} else {
 					if pub_pos != -1 {
 						p.error('redefinition of `pub` section')
+						return ast.StructDecl{}
 					}
 					pub_pos = fields.len
 					is_field_pub = true
@@ -119,6 +125,7 @@ fn (mut p Parser) struct_decl() ast.StructDecl {
 			} else if p.tok.kind == .key_mut {
 				if mut_pos != -1 {
 					p.error('redefinition of `mut` section')
+					return ast.StructDecl{}
 				}
 				p.next()
 				p.check(.colon)
@@ -129,6 +136,7 @@ fn (mut p Parser) struct_decl() ast.StructDecl {
 			} else if p.tok.kind == .key_global {
 				if global_pos != -1 {
 					p.error('redefinition of `global` section')
+					return ast.StructDecl{}
 				}
 				p.next()
 				p.check(.colon)
@@ -172,6 +180,7 @@ fn (mut p Parser) struct_decl() ast.StructDecl {
 				field_name = symbol_name
 				if typ in embedded_structs {
 					p.error_with_pos('cannot embed `$field_name` more than once', type_pos)
+					return ast.StructDecl{}
 				}
 				embedded_structs << typ
 			} else {
@@ -275,6 +284,7 @@ fn (mut p Parser) struct_decl() ast.StructDecl {
 	if ret == -1 {
 		p.error_with_pos('cannot register struct `$name`, another type with this name exists',
 			name_pos)
+		return ast.StructDecl{}
 	}
 	p.expr_mod = ''
 	return ast.StructDecl{
@@ -390,6 +400,7 @@ fn (mut p Parser) interface_decl() ast.InterfaceDecl {
 	if reg_idx == -1 {
 		p.error_with_pos('cannot register interface `$interface_name`, another type with this name exists',
 			name_pos)
+		return ast.InterfaceDecl{}
 	}
 	typ := table.new_type(reg_idx)
 	mut ts := p.table.get_type_symbol(typ)
@@ -403,9 +414,11 @@ fn (mut p Parser) interface_decl() ast.InterfaceDecl {
 		name := p.check_name()
 		if ts.has_method(name) {
 			p.error_with_pos('duplicate method `$name`', method_start_pos)
+			return ast.InterfaceDecl{}
 		}
 		if util.contains_capital(name) {
 			p.error('interface methods cannot contain uppercase letters, use snake_case instead')
+			return ast.InterfaceDecl{}
 		}
 		// field_names << name
 		args2, _, _ := p.fn_args() // TODO merge table.Param and ast.Arg to avoid this

vlib/v/pref/pref.v

@@ -123,6 +123,7 @@ pub mut:
 	skip_running        bool // when true, do no try to run the produced file (set by b.cc(), when -o x.c or -o x.js)
 	skip_warnings       bool // like C's "-w"
 	warns_are_errors    bool // -W, like C's "-Werror", treat *every* warning is an error
+	fatal_errors        bool // unconditionally exit after the first error with exit(1)
 	reuse_tmpc          bool // do not use random names for .tmp.c and .tmp.c.rsp files, and do not remove them
 	use_color           ColorOutput // whether the warnings/errors should use ANSI color escapes.
 	is_parallel         bool
@@ -172,6 +173,9 @@ pub fn parse_args(args []string) (&Preferences, string) {
 			'-progress' {
 				// processed by testing tools in cmd/tools/modules/testing/common.v
 			}
+			'-Wfatal-errors' {
+				res.fatal_errors = true
+			}
 			'-silent' {
 				res.output_mode = .silent
 			}

vlib/v/scanner/scanner.v

@@ -1236,6 +1236,9 @@ pub fn (mut s Scanner) error(msg string) {
 		eprintln(util.formatted_error('error:', msg, s.file_path, pos))
 		exit(1)
 	} else {
+		if s.pref.fatal_errors {
+			exit(1)
+		}
 		s.errors << errors.Error{
 			file_path: s.file_path
 			pos: pos