all: fix immutable fn args

compiler/fn.v

@@ -666,6 +666,7 @@ fn (p mut Parser) fn_args(f mut Fn) {
 		}
 		f.args << int_arg
 	}
+	// `(int, string, int)` 
 	// Just register fn arg types
 	types_only := p.tok == .mul || (p.peek() == .comma && p.table.known_type(p.lit)) || p.peek() == .rpar// (int, string)
 	if types_only {
@@ -684,12 +685,12 @@ fn (p mut Parser) fn_args(f mut Fn) {
 			}
 		}
 	}
-	// (a int, b,c string) syntax
+	// `(a int, b, c string)` syntax
 	for p.tok != .rpar {
 		mut names := [
 		p.check_name()
 		]
-		// a,b,c int syntax
+		// `a,b,c int` syntax
 		for p.tok == .comma {
 			p.check(.comma)
 			p.fspace()

vlib/builtin/string.v

@@ -694,13 +694,13 @@ pub fn (s string) ustring_tmp() ustring {
 	return res
 }
 
-pub fn (u ustring) substr(start, end int) string {
-	start = u.runes[start]
-	if end >= u.runes.len {
-		end = u.s.len
+pub fn (u ustring) substr(_start, _end int) string {
+	start := u.runes[_start]
+	end := if _end >= u.runes.len {
+		u.s.len
 	}
 	else {
-		end = u.runes[end]
+		u.runes[_end]
 	}
 	return u.s.substr(start, end)
 }

vlib/math/math.v

@@ -102,7 +102,8 @@ pub fn exp(a f64) f64 {
 }
 
 // digits returns an array of the digits of n in the given base.
-pub fn digits(n, base int) []int {
+pub fn digits(_n, base int) []int {
+	mut n := _n 
 	mut sign := 1
 	if n < 0 {
 		sign = -1
@@ -132,6 +133,7 @@ pub fn exp2(a f64) f64 {
 }
 
 // factorial calculates the factorial of the provided value.
+// TODO bring back once multiple value functions are implemented 
 fn recursive_product( n int, current_number_ptr &int) int{
     mut m := n / 2
     if (m == 0){

vlib/os/os.v

@@ -337,8 +337,8 @@ fn popen(path string) *FILE {
 }
 
 // exec starts the specified command, waits for it to complete, and returns its output.
-pub fn exec(cmd string) string {
-	cmd = '$cmd 2>&1'
+pub fn exec(_cmd string) string {
+	cmd := '$_cmd 2>&1'
 	f := popen(cmd)
 	if isnil(f) {
 		// TODO optional or error code 
@@ -397,19 +397,19 @@ pub fn unsetenv(name string) int {
 }
 
 // `file_exists` returns true if `path` exists.
-pub fn file_exists(path string) bool {
+pub fn file_exists(_path string) bool {
 	$if windows {
-		path = path.replace('/', '\\')
+		path := _path.replace('/', '\\')
 		return C._waccess(path.to_wide(), 0) != -1
 	} $else {
-		return C.access( path.str, 0 ) != -1
+		return C.access(_path.str, 0 ) != -1
 	}
 }
 
 pub fn dir_exists(path string) bool {
 	$if windows {
-		path = path.replace('/', '\\')
-		attr := int(C.GetFileAttributes(path.to_wide()))
+		_path := path.replace('/', '\\')
+		attr := int(C.GetFileAttributes(_path.to_wide()))
 		if attr == INVALID_FILE_ATTRIBUTES {
 			return false
 		}
@@ -431,13 +431,13 @@ pub fn dir_exists(path string) bool {
 // mkdir creates a new directory with the specified path.
 pub fn mkdir(path string) {
 	$if windows {
-		path = path.replace('/', '\\')
+		_path := path.replace('/', '\\')
 		// Windows doesnt recursively create the folders
 		// so we need to help it out here
-		if path.last_index('\\') != -1 {
-			mkdir(path.all_before_last('\\'))
+		if _path.last_index('\\') != -1 {
+			mkdir(_path.all_before_last('\\'))
 		}
-		C.CreateDirectory(path.to_wide(), 0)
+		C.CreateDirectory(_path.to_wide(), 0)
 	}
 	$else {
 		C.mkdir(path.str, 511)// S_IRWXU | S_IRWXG | S_IRWXO

vlib/strings/builder.v

@@ -34,7 +34,7 @@ pub fn (b Builder) str() string {
 	return string(b.buf, b.len)
 }
 
-pub fn (b Builder) cut(n int) {
+pub fn (b mut Builder) cut(n int) {
 	b.len -= n
 }