all: remove `it` smartcast and replace with original variable name (#5764)

cmd/tools/check_os_api_parity.v

@@ -98,9 +98,9 @@ fn (app App) gen_api_for_module_in_os(mod_name, os_name string) string {
 	for f in b.parsed_files {
 		for s in f.stmts {
 			if s is ast.FnDecl {
-				if it.is_pub {
+				if s.is_pub {
-					fn_signature := it.stringify(b.table)
+					fn_signature := s.stringify(b.table)
-					fn_mod := it.modname()
+					fn_mod := s.modname()
 					if fn_mod == mod_name {
 						fline := '${fn_mod}: $fn_signature'
 						res << fline

doc/docs.md

@@ -98,7 +98,7 @@ fn main() {
 ```
 Save that snippet into a file `hello.v` . Now do: `v run hello.v` .
 
-> That is assuming you have symlinked your V with `v symlink`, as described 
+> That is assuming you have symlinked your V with `v symlink`, as described
 [here](https://github.com/vlang/v/blob/master/README.md#symlinking).
 If you have not yet, you have to type the path to V manually.
 
@@ -108,7 +108,7 @@ Congratulations - you just wrote your first V program, and executed it!
 See `v help` for all supported commands.
 
 In the above example, you can see that functions are declared with `fn`.
-The return type goes after the function name. In this case `main` doesn't 
+The return type goes after the function name. In this case `main` doesn't
 return anything, so the return type can be omitted.
 
 As in many other languages (such as C, Go and Rust), `main` is an entry point.
@@ -541,6 +541,32 @@ else {
 println(s) // "odd"
 ```
 
+#### Is check
+You can check sum types using `if` like `match`ing them.
+```v
+struct Abc {
+    val string
+}
+struct Xyz {
+    foo string
+}
+type Alphabet = Abc | Xyz
+
+x := Alphabet(Abc{'test'}) // sum type
+if x is Abc {
+    // x is automatically castet to Abc and can be used here
+    println(x)
+}
+```
+
+If you have a struct field which should be checked, there is also a way to name a alias.
+```
+if x.bar is MyStruct as bar {
+    // x.bar cannot be castet automatically, instead you say "as bar" which creates a variable with the MyStruct typing
+    println(bar)
+}
+```
+
 ### In operator
 
 `in` allows to check whether an array or a map contains an element.
@@ -1851,9 +1877,9 @@ eprintln('$vm.name $vm.version\n $vm.description')
 
 ## Performance tuning
 
-The generated C code is usually fast enough, when you compile your code 
+The generated C code is usually fast enough, when you compile your code
-with `-prod`. There are some situations though, where you may want to give 
+with `-prod`. There are some situations though, where you may want to give
-additional hints to the C compiler, so that it can further optimize some 
+additional hints to the C compiler, so that it can further optimize some
 blocks of code.
 
 NB: These are *rarely* needed, and should not be used, unless you
@@ -1862,11 +1888,11 @@ To cite gcc's documentation: "programmers are notoriously bad at predicting
 how their programs actually perform".
 
 `[inline]` - you can tag functions with `[inline]`, so the C compiler will
-try to inline them, which in some cases, may be beneficial for performance, 
+try to inline them, which in some cases, may be beneficial for performance,
 but may impact the size of your executable.
 
-`if _likely_(bool expression) {` this hints the C compiler, that the passed 
+`if _likely_(bool expression) {` this hints the C compiler, that the passed
-boolean expression is very likely to be true, so it can generate assembly 
+boolean expression is very likely to be true, so it can generate assembly
 code, with less chance of branch misprediction. In the JS backend,
 that does nothing.
 
@@ -2106,7 +2132,7 @@ On Unix-like platforms, the file can be run directly after making it executable
 
 V has several attributes that modify the behavior of functions and structs.
 
-An attribute is specified inside `[]` right before the function/struct declaration and applies only to the following definition. 
+An attribute is specified inside `[]` right before the function/struct declaration and applies only to the following definition.
 
 ```v
 // Calling this function will result in a deprecation warning
@@ -2132,7 +2158,7 @@ fn bar() {
 }
 
 // For C interop only, tells V that the following struct is defined with `typedef struct` in C
-[typedef] 
+[typedef]
 struct C.Foo { }
 
 // Declare a function with WINAPI

examples/lander.v

@@ -33,7 +33,7 @@ fn wait() {
 
 fn (l Lander) land(w World) {
 	if w is Mars {
-		for it.dust_storm() {
+		for w.dust_storm() {
 			wait()
 		}
 	}

vlib/v/ast/ast.v

@@ -389,13 +389,13 @@ pub fn (i &Ident) var_info() IdentVar {
 
 pub struct InfixExpr {
 pub:
-	op         token.Kind
+	op           token.Kind
-	pos        token.Position
+	pos          token.Position
-	left       Expr
+	left         Expr
-	right      Expr
+	right        Expr
 pub mut:
-	left_type  table.Type
+	left_type    table.Type
-	right_type table.Type
+	right_type   table.Type
 }
 
 pub struct PostfixExpr {
@@ -443,6 +443,7 @@ pub:
 	comments []Comment
 pub mut:
 	smartcast bool // should only be true if cond is `x is sumtype`, it will be set in checker - if_expr
+	left_as_name string // only used in x is SumType check
 }
 
 pub struct LockExpr {

vlib/v/ast/str.v

@@ -279,7 +279,7 @@ pub fn (node Stmt) str() string {
 			mut out := ''
 			for i, left in it.left {
 				if left is Ident {
-					var_info := it.var_info()
+					var_info := left.var_info()
 					if var_info.is_mut {
 						out += 'mut '
 					}

vlib/v/builder/builder.v

@@ -288,8 +288,8 @@ fn (b &Builder) print_warnings_and_errors() {
 			for file in b.parsed_files {
 				for stmt in file.stmts {
 					if stmt is ast.FnDecl {
-						if it.name == fn_name {
+						if stmt.name == fn_name {
-							fline := it.pos.line_nr
+							fline := stmt.pos.line_nr
 							println('$file.path:$fline:')
 						}
 					}

vlib/v/checker/checker.v

@@ -207,17 +207,17 @@ fn (mut c Checker) check_file_in_main(file ast.File) bool {
 			}
 			ast.TypeDecl {
 				if stmt is ast.AliasTypeDecl {
-					if it.is_pub {
+					if stmt.is_pub {
-						c.warn('type alias `$it.name` $no_pub_in_main_warning',
+						c.warn('type alias `$stmt.name` $no_pub_in_main_warning',
-							it.pos)
+							stmt.pos)
 					}
 				} else if stmt is ast.SumTypeDecl {
-					if it.is_pub {
+					if stmt.is_pub {
-						c.warn('sum type `$it.name` $no_pub_in_main_warning', it.pos)
+						c.warn('sum type `$stmt.name` $no_pub_in_main_warning', stmt.pos)
 					}
 				} else if stmt is ast.FnTypeDecl {
-					if it.is_pub {
+					if stmt.is_pub {
-						c.warn('type alias `$it.name` $no_pub_in_main_warning', it.pos)
+						c.warn('type alias `$stmt.name` $no_pub_in_main_warning', stmt.pos)
 					}
 				}
 			}
@@ -1266,25 +1266,25 @@ fn (mut c Checker) type_implements(typ, inter_typ table.Type, pos token.Position
 // return the actual type of the expression, once the optional is handled
 pub fn (mut c Checker) check_expr_opt_call(expr ast.Expr, ret_type table.Type) table.Type {
 	if expr is ast.CallExpr {
-		if it.return_type.has_flag(.optional) {
+		if expr.return_type.has_flag(.optional) {
-			if it.or_block.kind == .absent {
+			if expr.or_block.kind == .absent {
 				if ret_type != table.void_type {
-					c.error('${it.name}() returns an option, but you missed to add an `or {}` block to it',
+					c.error('${expr.name}() returns an option, but you missed to add an `or {}` block to it',
-						it.pos)
+						expr.pos)
 				}
 			} else {
-				c.check_or_expr(it.or_block, ret_type)
+				c.check_or_expr(expr.or_block, ret_type)
 			}
 			// remove optional flag
 			// return ret_type.clear_flag(.optional)
 			// TODO: currently unwrapped in assign, would need to refactor assign to unwrap here
 			return ret_type
-		} else if it.or_block.kind == .block {
+		} else if expr.or_block.kind == .block {
-			c.error('unexpected `or` block, the function `$it.name` does not return an optional',
+			c.error('unexpected `or` block, the function `$expr.name` does not return an optional',
-				it.pos)
+				expr.pos)
-		} else if it.or_block.kind == .propagate {
+		} else if expr.or_block.kind == .propagate {
-			c.error('unexpected `?`, the function `$it.name`, does not return an optional',
+			c.error('unexpected `?`, the function `$expr.name`, does not return an optional',
-				it.pos)
+				expr.pos)
 		}
 	}
 	return ret_type
@@ -1522,7 +1522,7 @@ pub fn (mut c Checker) assign_stmt(mut assign_stmt ast.AssignStmt) {
 	}
 	if assign_stmt.left.len != right_len {
 		if right_first is ast.CallExpr {
-			c.error('assignment mismatch: $assign_stmt.left.len variable(s) but `${it.name}()` returns $right_len value(s)',
+			c.error('assignment mismatch: $assign_stmt.left.len variable(s) but `${right_first.name}()` returns $right_len value(s)',
 				assign_stmt.pos)
 		} else {
 			c.error('assignment mismatch: $assign_stmt.left.len variable(s) $right_len value(s)',
@@ -2620,27 +2620,30 @@ pub fn (mut c Checker) if_expr(mut node ast.IfExpr) table.Type {
 		// smartcast sumtypes when using `is`
 		if branch.cond is ast.InfixExpr {
 			infix := branch.cond as ast.InfixExpr
-			if infix.op == .key_is && infix.left is ast.Ident && infix.right is ast.Type {
+			if infix.op == .key_is && (infix.left is ast.Ident || infix.left is ast.SelectorExpr) &&  infix.right is ast.Type {
-				left_expr := infix.left as ast.Ident
 				right_expr := infix.right as ast.Type
-				if left_expr.kind == .variable {
+				is_variable := if infix.left is ast.Ident {
-					// Register shadow variable or `as` variable with actual type
+					(infix.left as ast.Ident).kind == .variable
+				} else { true }
+				// Register shadow variable or `as` variable with actual type
+				if is_variable {
 					left_sym := c.table.get_type_symbol(infix.left_type)
-					if left_sym.kind == .sum_type {
+					if left_sym.kind == .sum_type && branch.left_as_name.len > 0 {
+						mut is_mut := false
+						if infix.left is ast.Ident {
+							is_mut = (infix.left as ast.Ident).is_mut
+						} else if infix.left is ast.SelectorExpr {
+							selector := infix.left as ast.SelectorExpr
+							field := c.table.struct_find_field(left_sym, selector.field_name) or { table.Field{} }
+							is_mut = field.is_mut
+						}
 						mut scope := c.file.scope.innermost(branch.body_pos.pos)
-						scope.register('it', ast.Var{
+						scope.register(branch.left_as_name, ast.Var{
-							name: 'it'
+							name: branch.left_as_name
 							typ: right_expr.typ.to_ptr()
-							pos: left_expr.pos
+							pos: infix.left.position()
 							is_used: true
-							is_mut: left_expr.is_mut
+							is_mut: is_mut
-						})
-						scope.register(left_expr.name, ast.Var{
-							name: left_expr.name
-							typ: right_expr.typ.to_ptr()
-							pos: left_expr.pos
-							is_used: true
-							is_mut: left_expr.is_mut
 						})
 						node.branches[i].smartcast = true
 					}

vlib/v/checker/tests/returns/return_missing_simple.vv

@@ -0,0 +1,7 @@
+fn foo() string {
+	if true {
+		return ''
+	} else {
+		
+	}
+}

vlib/v/doc/doc.v

@@ -45,7 +45,7 @@ pub fn merge_comments(stmts []ast.Stmt) string {
 	mut res := []string{}
 	for s in stmts {
 		if s is ast.Comment {
-			res << it.text.trim_left('|')
+			res << s.text.trim_left('|')
 		}
 	}
 	return res.join('\n')
@@ -374,11 +374,11 @@ fn (mut d Doc) generate() ?Doc {
 				continue
 			}
 			if stmt is ast.FnDecl {
-				if it.is_deprecated {
+				if stmt.is_deprecated {
 					continue
 				}
-				if it.receiver.typ != 0 {
+				if stmt.receiver.typ != 0 {
-					node.attrs['parent'] = d.fmt.type_to_str(it.receiver.typ).trim_left('&')
+					node.attrs['parent'] = d.fmt.type_to_str(stmt.receiver.typ).trim_left('&')
 					p_idx := d.contents.index_by_name(node.attrs['parent'])
 					if p_idx == -1 && node.attrs['parent'] != 'void' {
 						d.contents << DocNode{

vlib/v/fmt/fmt.v

@@ -246,7 +246,7 @@ pub fn (mut f Fmt) stmt(node ast.Stmt) {
 		ast.AssignStmt {
 			for i, left in node.left {
 				if left is ast.Ident {
-					var_info := it.var_info()
+					var_info := left.var_info()
 					if var_info.is_mut {
 						f.write('mut ')
 					}
@@ -660,8 +660,8 @@ pub fn (mut f Fmt) prefix_expr_cast_expr(fexpr ast.Expr) {
 	mut is_pe_amp_ce := false
 	mut ce := ast.CastExpr{}
 	if fexpr is ast.PrefixExpr {
-		if it.right is ast.CastExpr && it.op == .amp {
+		if fexpr.right is ast.CastExpr && fexpr.op == .amp {
-			ce = it.right as ast.CastExpr
+			ce = fexpr.right as ast.CastExpr
 			ce.typname = f.table.get_type_symbol(ce.typ).name
 			is_pe_amp_ce = true
 			f.expr(ce)
@@ -1248,16 +1248,16 @@ pub fn (mut f Fmt) call_expr(node ast.CallExpr) {
 		}
 		*/
 		if node.left is ast.Ident {
-			it := node.left as ast.Ident
+			left := node.left as ast.Ident
 			// `time.now()` without `time imported` is processed as a method call with `time` being
 			// a `node.left` expression. Import `time` automatically.
 			// TODO fetch all available modules
-			if it.name in ['time', 'os', 'strings', 'math', 'json', 'base64'] {
+			if left.name in ['time', 'os', 'strings', 'math', 'json', 'base64'] {
-				if it.name !in f.auto_imports {
+				if left.name !in f.auto_imports {
-					f.auto_imports << it.name
+					f.auto_imports << left.name
 					f.file.imports << ast.Import{
-						mod: it.name
+						mod: left.name
-						alias: it.name
+						alias: left.name
 					}
 				}
 				// for imp in f.file.imports {
@@ -1321,7 +1321,7 @@ pub fn (mut f Fmt) match_expr(it ast.MatchExpr) {
 		stmt := branch.stmts[0]
 		if stmt is ast.ExprStmt {
 			// If expressions inside match branches can't be one a single line
-			if !expr_is_single_line(it.expr) {
+			if !expr_is_single_line(stmt.expr) {
 				single_line = false
 				break
 			}

vlib/v/gen/cgen.v

@@ -1213,12 +1213,12 @@ fn (mut g Gen) gen_assign_stmt(assign_stmt ast.AssignStmt) {
 		mut blank_assign := false
 		mut ident := ast.Ident{}
 		if left is ast.Ident {
-			ident = it
+			ident = *left
 			// id_info := ident.var_info()
 			// var_type = id_info.typ
-			blank_assign = ident.kind == .blank_ident
+			blank_assign = left.kind == .blank_ident
-			if ident.info is ast.IdentVar {
+			if left.info is ast.IdentVar {
-				share := (ident.info as ast.IdentVar).share
+				share := (left.info as ast.IdentVar).share
 				if share == .shared_t {
 					var_type = var_type.set_flag(.shared_f)
 				}
@@ -1390,9 +1390,9 @@ fn (mut g Gen) gen_cross_tmp_variable(left []ast.Expr, val ast.Expr) {
 			mut has_var := false
 			for lx in left {
 				if lx is ast.Ident {
-					if val.name == it.name {
+					if val.name == lx.name {
 						g.write('_var_')
-						g.write(it.pos.pos.str())
+						g.write(lx.pos.pos.str())
 						has_var = true
 						break
 					}
@@ -2322,9 +2322,8 @@ fn (mut g Gen) if_expr(node ast.IfExpr) {
 			infix := branch.cond as ast.InfixExpr
 			right_type := infix.right as ast.Type
 			left_type := infix.left_type
-			left_expr := infix.left as ast.Ident
 			it_type := g.typ(right_type.typ)
-			g.write('\t$it_type* it = ($it_type*)')
+			g.write('\t$it_type* _sc_tmp_$branch.pos.pos = ($it_type*)')
 			g.expr(infix.left)
 			if left_type.is_ptr() {
 				g.write('->')
@@ -2332,7 +2331,7 @@ fn (mut g Gen) if_expr(node ast.IfExpr) {
 				g.write('.')
 			}
 			g.writeln('obj;')
-			g.writeln('\t$it_type* $left_expr.name = it;')
+			g.writeln('\t$it_type* $branch.left_as_name = _sc_tmp_$branch.pos.pos;')
 		}
 		g.stmts(branch.stmts)
 	}

vlib/v/gen/comptime.v

@@ -12,9 +12,9 @@ fn (g &Gen) comptime_call(node ast.ComptimeCall) {
 		for stmt in node.vweb_tmpl.stmts {
 			if stmt is ast.FnDecl {
 				// insert stmts from vweb_tmpl fn
-				if it.name.starts_with('main.vweb_tmpl') {
+				if stmt.name.starts_with('main.vweb_tmpl') {
 					g.inside_vweb_tmpl = true
-					g.stmts(it.stmts)
+					g.stmts(stmt.stmts)
 					g.inside_vweb_tmpl = false
 					break
 				}

vlib/v/gen/js/js.v

@@ -686,8 +686,8 @@ fn (mut g JsGen) gen_assign_stmt(stmt ast.AssignStmt) {
 			val := stmt.right[i]
 			mut is_mut := false
 			if left is ast.Ident {
-				is_mut = it.is_mut
+				is_mut = left.is_mut
-				if it.kind == .blank_ident || it.name in ['', '_'] {
+				if left.kind == .blank_ident || left.name in ['', '_'] {
 					tmp_var := g.new_tmp_var()
 					// TODO: Can the tmp_var declaration be omitted?
 					g.write('const $tmp_var = ')

vlib/v/parser/assign.v

@@ -15,7 +15,7 @@ fn (mut p Parser) check_undefined_variables(exprs []ast.Expr, val ast.Expr) {
 		ast.Ident {
 			for expr in exprs {
 				if expr is ast.Ident {
-					if it.name == val.name {
+					if expr.name == val.name {
 						p.error_with_pos('undefined variable: `$val.name`', val.pos)
 					}
 				}
@@ -49,7 +49,7 @@ fn (mut p Parser) check_cross_variables(exprs []ast.Expr, val ast.Expr) bool {
 		ast.Ident {
 			for expr in exprs {
 				if expr is ast.Ident {
-					if it.name == val_.name {
+					if expr.name == val_.name {
 						return true
 					}
 				}

vlib/v/parser/comptime.v

@@ -129,13 +129,12 @@ fn (mut p Parser) vweb() ast.ComptimeCall {
 	// copy vars from current fn scope into vweb_tmpl scope
 	for stmt in file.stmts {
 		if stmt is ast.FnDecl {
-			if it.name == 'main.vweb_tmpl_$p.cur_fn_name' {
+			if stmt.name == 'main.vweb_tmpl_$p.cur_fn_name' {
-				fn_decl := it
+				tmpl_scope := file.scope.innermost(stmt.body_pos.pos)
-				tmpl_scope := file.scope.innermost(it.body_pos.pos)
 				for _, obj in p.scope.objects {
 					if obj is ast.Var {
-						mut v := it
+						mut v := obj
-						v.pos = fn_decl.body_pos
+						v.pos = stmt.body_pos
 						tmpl_scope.register(v.name, *v)
 						// set the controller action var to used
 						// if its unused in the template it will warn

vlib/v/parser/fn.v

@@ -555,7 +555,7 @@ fn (mut p Parser) fn_redefinition_error(name string) {
 fn have_fn_main(stmts []ast.Stmt) bool {
 	for stmt in stmts {
 		if stmt is ast.FnDecl {
-			if it.name == 'main.main' && it.mod == 'main' {
+			if stmt.name == 'main.main' && stmt.mod == 'main' {
 				return true
 			}
 		}

vlib/v/parser/if.v

@@ -64,9 +64,25 @@ fn (mut p Parser) if_expr() ast.IfExpr {
 		} else {
 			cond = p.expr(0)
 		}
+		mut left_as_name := ''
+		is_infix := cond is ast.InfixExpr
+		if is_infix {
+			infix := cond as ast.InfixExpr
+			is_is_cast := infix.op == .key_is
+			is_ident := infix.left is ast.Ident
+			left_as_name = if is_is_cast && p.tok.kind == .key_as {
+				p.next()
+				p.check_name()
+			} else if is_ident {
+				ident := infix.left as ast.Ident
+				ident.name
+			} else {
+				''
+			}
+		}
 		end_pos := p.prev_tok.position()
 		body_pos := p.tok.position()
-		p.inside_if = false		
+		p.inside_if = false
 		stmts := p.parse_block()
 		if is_or {
 			p.close_scope()
@@ -77,6 +93,7 @@ fn (mut p Parser) if_expr() ast.IfExpr {
 			pos: start_pos.extend(end_pos)
 			body_pos: body_pos.extend(p.tok.position())
 			comments: comments
+			left_as_name: left_as_name
 		}
 		comments = []
 		if p.tok.kind != .key_else {

vlib/v/parser/pratt.v

@@ -230,6 +230,10 @@ pub fn (mut p Parser) expr(precedence int) ast.Expr {
 			}
 			// continue on infix expr
 			node = p.infix_expr(node)
+			// return early `if bar is SumType as b {`
+			if p.tok.kind == .key_as && p.inside_if {
+				return node
+			}
 		} else if p.tok.kind in [.inc, .dec] {
 			// Postfix
 			node = ast.PostfixExpr{

vlib/v/tests/if_smartcast_test.v

@@ -0,0 +1,60 @@
+struct Abc {
+mut:
+	val string
+}
+struct Xyz {
+	name string
+}
+type Alphabet = Abc | Xyz
+
+fn test_if_smartcast() {
+	x := Alphabet(Abc{'test'})
+	if x is Abc {
+		assert x.val == 'test'
+	}
+}
+
+fn test_mutable() {
+	mut x := Alphabet(Abc{'test'})
+	if x is Abc {
+		y := Abc{}
+		x = &y
+		assert x == &y
+	}
+}
+
+fn test_nested_if_smartcast() {
+	x := Alphabet(Abc{'test'})
+	y := Alphabet(Xyz{'foo'})
+	if x is Abc {
+		if y is Xyz {
+			assert y.name == 'foo'
+		}
+	}
+}
+
+fn test_as_cast() {
+	x := Alphabet(Abc{'test'})
+	if x is Abc as test {
+		assert test.val == 'test'
+	}
+}
+
+struct Test {
+	abc Alphabet
+}
+
+fn test_mutable_with_struct() {
+	mut x := Test{Abc{'test'}}
+	if x.abc is Abc as test {
+		test.val = 'test'
+		assert test.val == 'test'
+	}
+}
+
+fn test_as_cast_with_struct() {
+	x := Test{Abc{'test'}}
+	if x.abc is Abc as test {
+		assert test.val == 'test'
+	}
+}