parser: disallow statements after a return, branch check $if, $else, switch, and loops correctly

compiler/cgen.v

@@ -263,7 +263,6 @@ fn build_thirdparty_obj_file(flag string) {
 	cc := if os.user_os() == 'windows' { 'gcc' } else { 'cc' } // TODO clang support on Windows  
 	res := os.exec('$cc -fPIC -c -o $obj_path $cfiles') or {
 		panic(err)
-		return // TODO remove return
 	}
 	println(res) 
 } 

compiler/comptime.v

@@ -39,6 +39,20 @@ fn (p mut Parser) comp_time() {
 			println(SupportedPlatforms)
 			p.error('unknown platform `$name`')
 		}
+		if_returns := p.returns
+		p.returns = false
+		p.gen('/* returns $p.returns */')
+		if p.tok == .dollar && p.peek() == .key_else {
+			p.next()
+			p.next()
+			p.check(.lcbr)
+			p.genln('#else')
+			p.statements_no_rcbr()
+			p.genln('#endif')
+			else_returns := p.returns
+			p.returns = if_returns && else_returns
+		p.gen('/* returns $p.returns */')
+		}
 	}
 	else if p.tok == .key_for {
 		p.next()
@@ -65,13 +79,6 @@ fn (p mut Parser) comp_time() {
 		p.check(.rcbr)
 		// }
 	}
-	else if p.tok == .key_else {
-		p.next()
-		p.check(.lcbr)
-		p.genln('#else')
-		p.statements_no_rcbr()
-		p.genln('#endif')
-	}
 	// $vweb.html() 
 	// Compile vweb html template to V code, parse that V code and embed the resulting V functions
 	// that returns an html string 

compiler/fn.v

@@ -124,6 +124,7 @@ fn (p mut Parser) fn_decl() {
 		p.next()
 	}
 	p.returns = false
+		p.gen('/* returns $p.returns */')
 	p.next()
 	mut f := new_fn(p.mod, is_pub)
 	// Method receiver

compiler/main.v

@@ -139,14 +139,12 @@ fn main() {
 			vexec := os.args[0] 
 			_ := os.exec('$vexec vget.v') or {
 				panic(err)
-				return // TODO remove return
 			}
 			//println('Done.') 
 		}
 		println('Installing module ${mod}...') 
 		_ := os.exec('$vget $mod') or {
 			panic(err)
-			return // TODO remove return
 		}
 		return 
 	} 
@@ -891,7 +889,6 @@ mut args := ''
 		}
 		panic('C error. This should never happen. ' +
 			'Please create a GitHub issue: https://github.com/vlang/v/issues/new/choose')
-		return // TODO remove return
 	}
 	diff := time.ticks() - ticks 
 	// Print the C command
@@ -914,7 +911,6 @@ mut args := ''
 		' /usr/lib/x86_64-linux-gnu/libc.so ' +
 		'/usr/lib/x86_64-linux-gnu/crtn.o') or {
 			panic(err)
-			return // TODO remove return
 		}
 		println(ress)
 		println('linux cross compilation done. resulting binary: "$v.out_name"')
@@ -1226,7 +1222,7 @@ fn new_v(args[]string) *V {
  
 	}  else {
 		println('vlib not found. It should be next to the V executable. ')  
-		println('Go to https://vlang.io to install V.') 
+		println('Go to https://vlang.io to install V.')
 		exit(1) 
 	} 
 	mut out_name_c := out_name.all_after('/') + '.c'
@@ -1327,7 +1323,6 @@ fn run_repl() []string {
 			os.write_file(file, source_code)
 			s := os.exec('$vexe run $file -repl') or {
 				panic(err)
-				break // TODO remove break
 			}
 			vals := s.split('\n')
 			for i:=0; i < vals.len; i++ {
@@ -1345,7 +1340,6 @@ fn run_repl() []string {
 			os.write_file(temp_file, temp_source_code)
 			s := os.exec('$vexe run $temp_file -repl') or {
 				panic(err)
-				break // TODO remove break
 			}
 			lines << line
 			vals := s.split('\n')
@@ -1411,20 +1405,17 @@ fn update_v() {
 	vroot := os.dir(os.executable()) 
 	s := os.exec('git -C "$vroot" pull --rebase origin master') or {
 		panic(err)
-		return // TODO remove return
 	}
 	println(s) 
 	$if windows { 
 		os.mv('$vroot/v.exe', '$vroot/v_old.exe') 
 		s2 := os.exec('$vroot/make.bat') or {
 			panic(err)
-			return // TODO remove return
 		}
 		println(s2) 
 	} $else { 
 		s2 := os.exec('make -C "$vroot"') or {
 			panic(err)
-			return // TODO remove return
 		}
 		println(s2) 
 	} 

compiler/msvc_win.v

@@ -28,37 +28,40 @@ const (
 	KEY_ENUMERATE_SUB_KEYS = (0x0008)
 )
 
-// Given a root key look for the subkey 'version' and get the path 
-fn find_windows_kit_internal(key RegKey, version string) ?string {
-	required_bytes := 0 // TODO mut 
-	result := C.RegQueryValueExW(key, version.to_wide(), 0, 0, 0, &required_bytes)
+// Given a root key look for one of the subkeys in 'versions' and get the path 
+fn find_windows_kit_internal(key RegKey, versions []string) ?string {
+	for version in versions {
+		required_bytes := 0 // TODO mut 
+		result := C.RegQueryValueExW(key, version.to_wide(), 0, 0, 0, &required_bytes)
 
-	length := required_bytes / 2
+		length := required_bytes / 2
 
-	if result != 0 {
-		return error('')
+		if result != 0 {
+			continue
+		}
+
+		alloc_length := (required_bytes + 2)
+
+		mut value := &u16(malloc(alloc_length))
+		if !value {
+			continue
+		}
+
+		result2 := C.RegQueryValueExW(key, version.to_wide(), 0, 0, value, &alloc_length)
+
+		if result2 != 0 {
+			continue
+		}
+
+		// We might need to manually null terminate this thing
+		// So just make sure that we do that
+		if (value[length - 1] != u16(0)) {
+			value[length] = u16(0)
+		}
+
+		return string_from_wide(value)
 	}
-
-	alloc_length := (required_bytes + 2)
-
-	mut value := &u16(malloc(alloc_length))
-	if !value {
-		return error('')
-	}
-
-	result2 := C.RegQueryValueExW(key, version.to_wide(), 0, 0, value, &alloc_length)
-
-	if result2 != 0 {
-		return error('')
-	}
-
-	// We might need to manually null terminate this thing
-	// So just make sure that we do that
-	if (value[length - 1] != u16(0)) {
-		value[length] = u16(0)
-	}
-
-	return string_from_wide(value)
+	return error('windows kit not found')
 }
 
 struct WindowsKit {
@@ -82,13 +85,8 @@ fn find_windows_kit_root() ?WindowsKit {
 		return error('Unable to open root key')
 	}
 	// Try and find win10 kit
-	kit_root := find_windows_kit_internal(root_key, 'KitsRoot10') or {
-		// Fallback to windows 8
-		k := find_windows_kit_internal(root_key, 'KitsRoot81') or {
-			println('Unable to find windows sdk')
-			return error('Unable to find a windows kit')
-		}
-		k
+	kit_root := find_windows_kit_internal(root_key, ['KitsRoot10', 'KitsRoot81']) or {
+		return error('Unable to find a windows kit')
 	}
 
 	kit_lib := kit_root + 'Lib'
@@ -135,8 +133,7 @@ fn find_vs() ?VsInstallation {
 	// If its not there then end user needs to update their visual studio 
 	// installation!
 	res := os.exec('""%ProgramFiles(x86)%\\Microsoft Visual Studio\\Installer\\vswhere.exe" -latest -products * -requires Microsoft.VisualStudio.Component.VC.Tools.x86.x64 -property installationPath"') or {
-		panic(err)
-		return error(err)// TODO remove return
+		return error(err)
 	}
 	// println('res: "$res"')
 
@@ -347,7 +344,6 @@ pub fn (v mut V) cc_msvc() {
 	_ := os.exec(cmd) or {
 		println(err)
 		panic('msvc error')
-		return // TODO remove return
 	}
 	// println(res)
 	// println('C OUTPUT:')
@@ -391,7 +387,6 @@ fn build_thirdparty_obj_file_with_msvc(flag string) {
 
 	res := os.exec('""$msvc.exe_path\\cl.exe" /volatile:ms /Z7 $include_string /c $cfiles /Fo"$obj_path" /D_UNICODE /DUNICODE"') or {
 		panic(err)
-		return // TODO remove return
 	}
 	println(res)
 } 

compiler/parser.v

@@ -102,7 +102,6 @@ fn platform_postfix_to_ifdefguard(name string) string {
     case '_mac.v': return '#ifdef __APPLE__'
   }
   panic('bad platform_postfix "$name"')
-  return ''
 }
 
 fn (v mut V) new_parser(path string, pass Pass) Parser {
@@ -296,7 +295,6 @@ fn (p mut Parser) parse() {
 			if false && !p.first_pass() && p.fileis('main.v') {
 				out := os.create('/var/tmp/fmt.v') or {
 					panic('failed to create fmt.v') 
-					return 
 				} 
 				out.writeln(p.scanner.fmt_out.str())
 				out.close()
@@ -1103,6 +1101,9 @@ fn (p mut Parser) vh_genln(s string) {
 }
 
 fn (p mut Parser) statement(add_semi bool) string {
+	if(p.returns) {
+		p.error('unreachable code')
+	}
 	p.cgen.is_tmp = false
 	tok := p.tok
 	mut q := ''
@@ -1321,6 +1322,7 @@ fn (p mut Parser) var_decl() {
 		if !p.returns && p.prev_tok2 != .key_continue && p.prev_tok2 != .key_break {
 			p.error('`or` block must return/continue/break/panic')
 		}
+		p.returns = false
 	}
 	p.register_var(Var {
 		name: name
@@ -1983,7 +1985,6 @@ fn (p mut Parser) index_expr(typ_ string, fn_ph int) string {
 			p.cgen.insert_before('$typ $tmp = $tmp_val;')
 		}
 		return typ
-		return 'void'
 	}
 	// else if p.pref.is_verbose && p.assigned_var != '' {
 	// p.error('didnt assign')
@@ -2905,7 +2906,6 @@ fn os_name_to_ifdef(name string) string {
 		case 'msvc': return '_MSC_VER' 
 	} 
 	panic('bad os ifdef name "$name"') 
-	return '' 
 } 
 
 fn (p mut Parser) if_st(is_expr bool, elif_depth int) string {
@@ -3167,6 +3167,7 @@ fn (p mut Parser) for_st() {
 	p.statements()
 	p.close_scope()
 	p.for_expr_cnt--
+	p.returns = false // TODO handle loops that are guaranteed to return
 }
 
 fn (p mut Parser) switch_statement() {
@@ -3180,7 +3181,9 @@ fn (p mut Parser) switch_statement() {
 	expr := p.cgen.end_tmp()
 	p.check(.lcbr)
 	mut i := 0
+	mut all_cases_return := true
 	for p.tok == .key_case || p.tok == .key_default || p.peek() == .arrow || p.tok == .key_else { 
+		p.returns = false
 		if p.tok == .key_default || p.tok == .key_else { 
 			p.genln('else  { // default:')
 			if p.tok == .key_default { 
@@ -3191,7 +3194,8 @@ fn (p mut Parser) switch_statement() {
 				p.check(.arrow)
 			} 
 			p.statements()
-			break
+			p.returns = all_cases_return && p.returns
+			return
 		}
 		if i > 0 {
 			p.gen('else ')
@@ -3228,8 +3232,10 @@ fn (p mut Parser) switch_statement() {
 		p.gen(')) {')
 		p.genln('/* case */')
 		p.statements()
+		all_cases_return = all_cases_return && p.returns
 		i++
 	}
+	p.returns = false // only get here when no default, so return is not guaranteed
 }
 
 fn (p mut Parser) assert_statement() {

compiler/scanner.v

@@ -33,7 +33,6 @@ fn new_scanner(file_path string) *Scanner {
 
 	mut raw_text := os.read_file(file_path) or {
 		panic('scanner: failed to open "$file_path"')
-		return &Scanner{}
 	}
 
 	// BOM check

compiler/table.v

@@ -739,8 +739,7 @@ fn (t mut Table) fn_gen_types(fn_name string) []string {
 			return f.types
 		} 
 	} 
-	panic('function $fn_name not found') // TODO panic or return []?
-	return []string // TODO remove return
+	panic('function $fn_name not found')
 } 
 
 // `foo<Bar>()`
@@ -830,7 +829,6 @@ fn (fit mut FileImportTable) register_import(mod string) {
 fn (fit mut FileImportTable) register_alias(alias string, mod string) {
 	if alias in fit.imports { 
 		panic('cannot import $mod as $alias: import name $alias already in use in "${fit.file_path}".')
-		return 
 	}
 	if mod.contains('.internal.') {
 		mod_parts := mod.split('.')

compiler/tests/option_test.v

@@ -19,7 +19,6 @@ fn err_call(ok bool) ?int {
 fn test_option_for_base_type_without_variable() {
 	val := err_call(true) or {
 		panic(err)
-		return
 	}
 	assert val == 42
 }