From 11b7b973119f9025dc8ed268a1c41af08dd1f9f5 Mon Sep 17 00:00:00 2001
From: Enzo Baldisserri <enzo.baldisserri@outlook.fr>
Date: Mon, 8 Jun 2020 00:47:04 +0200
Subject: [PATCH] parser: fail when assigning to _ with :=

---
 cmd/tools/bench/wyhash.v                      |  6 +-
 cmd/tools/vup.v                               |  2 +-
 examples/vweb/vweb_example.v                  |  2 +-
 vlib/builtin/array_test.v                     |  2 +-
 vlib/crypto/aes/block_generic.v               |  2 +-
 vlib/live/executable/reloader.v               |  2 +-
 vlib/net/ftp/ftp.v                            |  4 +-
 vlib/net/socket.v                             |  6 +-
 vlib/net/socket_udp_test.v                    |  2 +-
 vlib/rand/random_numbers_test.v               |  2 +-
 vlib/time/parse_test.v                        |  6 +-
 vlib/v/ast/ast.v                              |  8 ---
 vlib/v/checker/checker.v                      | 55 +++++++++++--------
 vlib/v/checker/tests/blank_modify.out         |  5 ++
 vlib/v/checker/tests/blank_modify.vv          |  3 +
 vlib/v/checker/tests/if_expr_last_stmt.out    |  2 +-
 vlib/v/checker/tests/if_expr_last_stmt.vv     |  2 +-
 vlib/v/checker/tests/if_expr_no_else.out      |  6 +-
 vlib/v/checker/tests/if_expr_no_else.vv       |  2 +-
 .../checker/tests/incorrect_name_variable.out |  2 +-
 .../checker/tests/incorrect_name_variable.vv  |  2 +-
 vlib/v/checker/tests/match_expr_else.vv       |  4 +-
 .../tests/no_interface_instantiation_a.out    |  6 +-
 .../tests/no_interface_instantiation_a.vv     |  2 +-
 vlib/v/checker/tests/selector_expr_assign.out |  6 ++
 vlib/v/checker/tests/selector_expr_assign.vv  |  8 +++
 vlib/v/checker/tests/struct_unknown_field.out |  4 +-
 vlib/v/checker/tests/struct_unknown_field.vv  |  8 +--
 vlib/v/checker/tests/unexpected_or.out        |  6 +-
 vlib/v/checker/tests/unexpected_or.vv         |  2 +-
 vlib/v/checker/tests/void_fn_as_value.out     | 12 ++--
 vlib/v/checker/tests/void_fn_as_value.vv      |  8 +--
 vlib/v/checker/tests/void_optional_err.vv     |  2 +-
 vlib/v/doc/doc.v                              |  2 +-
 vlib/v/gen/js/tests/js.v                      |  2 +-
 vlib/v/parser/assign.v                        | 12 ++--
 vlib/v/parser/parser.v                        | 23 +++++---
 vlib/v/table/table.v                          |  2 +-
 vlib/v/tests/array_init_test.v                |  8 +--
 vlib/v/tests/fn_high_test.v                   |  6 +-
 vlib/v/tests/vmod_parser_test.v               |  2 +-
 41 files changed, 137 insertions(+), 111 deletions(-)
 create mode 100644 vlib/v/checker/tests/blank_modify.out
 create mode 100644 vlib/v/checker/tests/blank_modify.vv
 create mode 100644 vlib/v/checker/tests/selector_expr_assign.out
 create mode 100644 vlib/v/checker/tests/selector_expr_assign.vv

diff --git a/cmd/tools/bench/wyhash.v b/cmd/tools/bench/wyhash.v
index 0f478914d2..203b83cbf2 100644
--- a/cmd/tools/bench/wyhash.v
+++ b/cmd/tools/bench/wyhash.v
@@ -24,7 +24,7 @@ fn main() {
 	for len in str_lens {
 		end_pos := start_pos + len
 		str := string(bytepile[start_pos..end_pos],len)
-		_ = wyhash.wyhash_c(&str.str, u64(str.len), 1)
+		wyhash.wyhash_c(&str.str, u64(str.len), 1)
 		start_pos = end_pos
 	}
 	t1 := time.ticks()
@@ -34,7 +34,7 @@ fn main() {
 	for len in str_lens {
 		end_pos := start_pos + len
 		str := string(bytepile[start_pos..end_pos],len)
-		_ = wyhash.sum64_string(str, 1)
+		wyhash.sum64_string(str, 1)
 		start_pos = end_pos
 	}
 	t2 := time.ticks()
@@ -44,7 +44,7 @@ fn main() {
 	for len in str_lens {
 		end_pos := start_pos + len
 		str := string(bytepile[start_pos..end_pos],len)
-		_ = fnv1a.sum64_string(str)
+		fnv1a.sum64_string(str)
 		start_pos = end_pos
 	}
 	t3 := time.ticks()
diff --git a/cmd/tools/vup.v b/cmd/tools/vup.v
index 6753031e61..8c8dcd8e78 100644
--- a/cmd/tools/vup.v
+++ b/cmd/tools/vup.v
@@ -56,7 +56,7 @@ fn main() {
 		}
 	}
 
-	_ := os.exec('v cmd/tools/vup.v') or {
+	os.exec('v cmd/tools/vup.v') or {
 		panic(err)
 	}
 	show_current_v_version(vexe)
diff --git a/examples/vweb/vweb_example.v b/examples/vweb/vweb_example.v
index 657bdf2f7d..26e89a6841 100644
--- a/examples/vweb/vweb_example.v
+++ b/examples/vweb/vweb_example.v
@@ -27,7 +27,7 @@ pub fn (mut app App) json_endpoint() {
 
 pub fn (mut app App) index() {
 	app.cnt++
-	show:= true
+	show := true
 	//app.vweb.text('Hello world from vweb')
 	hello := 'Hello world from vweb'
 	numbers := [1,2,3]
diff --git a/vlib/builtin/array_test.v b/vlib/builtin/array_test.v
index 62d35433dc..56de6422ec 100644
--- a/vlib/builtin/array_test.v
+++ b/vlib/builtin/array_test.v
@@ -593,7 +593,7 @@ fn test_array_str() {
 	numbers := [1, 2, 3]
 	assert numbers == [1,2,3]
 	numbers2 := [numbers, [4, 5, 6]] // dup str() bug
-	_=numbers2
+	_ = numbers2
 	assert true
 	assert numbers.str() == '[1, 2, 3]'
 	// QTODO
diff --git a/vlib/crypto/aes/block_generic.v b/vlib/crypto/aes/block_generic.v
index 6b63937917..cbeeda970d 100644
--- a/vlib/crypto/aes/block_generic.v
+++ b/vlib/crypto/aes/block_generic.v
@@ -84,7 +84,7 @@ fn encrypt_block_generic(xk []u32, dst, src []byte) {
 	s2 ^= xk[k+2]
 	s3 ^= xk[k+3]
 
-	_ = dst[15] // early bounds check
+	_ := dst[15] // early bounds check
 	binary.big_endian_put_u32(mut dst[..4], s0)
 	binary.big_endian_put_u32(mut dst.slice(4, 8), s1)
 	binary.big_endian_put_u32(mut dst.slice(8, 12), s2)
diff --git a/vlib/live/executable/reloader.v b/vlib/live/executable/reloader.v
index ac17dc0243..0020852a01 100644
--- a/vlib/live/executable/reloader.v
+++ b/vlib/live/executable/reloader.v
@@ -36,7 +36,7 @@ pub fn start_reloader(mut r live.LiveReloadInfo) {
 	// If that fails, the program would crash anyway, just provide
 	// an error message to the user and exit:
     r.reloads++
-	_ := compile_and_reload_shared_lib(mut r) or {
+	compile_and_reload_shared_lib(mut r) or {
 		eprintln( err )
 		exit(1)
 	}
diff --git a/vlib/net/ftp/ftp.v b/vlib/net/ftp/ftp.v
index f475b24df8..cd5c51b791 100644
--- a/vlib/net/ftp/ftp.v
+++ b/vlib/net/ftp/ftp.v
@@ -136,9 +136,7 @@ pub fn (ftp FTP) login(user, passwd string) bool {
 		}
 		return false
 	}
-	code, data = ftp.read()
-	// TODO Replace `data` with `_`
-	_ := data
+	code, _ = ftp.read()
 	if code == logged_in {
 		return true
 	}
diff --git a/vlib/net/socket.v b/vlib/net/socket.v
index c5c4325800..9c45972396 100644
--- a/vlib/net/socket.v
+++ b/vlib/net/socket.v
@@ -150,10 +150,10 @@ pub fn listen(port int) ?Socket {
 	s := new_socket(C.AF_INET, C.SOCK_STREAM, 0) or {
 		return error(err)
 	}
-	_ = s.bind(port) or {
+	s.bind(port) or {
 		return error(err)
 	}
-	_ = s.listen() or {
+	s.listen() or {
 		return error(err)
 	}
 	return s
@@ -212,7 +212,7 @@ pub fn dial(address string, port int) ?Socket {
 	s := new_socket(C.AF_INET, C.SOCK_STREAM, 0) or {
 		return error(err)
 	}
-	_ = s.connect(address, port) or {
+	s.connect(address, port) or {
 		return error(err)
 	}
 	return s
diff --git a/vlib/net/socket_udp_test.v b/vlib/net/socket_udp_test.v
index c9fd5bfad4..165d6cde6b 100644
--- a/vlib/net/socket_udp_test.v
+++ b/vlib/net/socket_udp_test.v
@@ -4,7 +4,7 @@ fn start_socket_udp_server() {
 	bufsize := 1024
 	bytes := [1024]byte
 	s := net.socket_udp() or { panic(err) }
-	_ = s.bind( 9876 ) or { panic(err) }
+	s.bind( 9876 ) or { panic(err) }
 	println('Waiting for udp packets:')
 	for {
 		res := s.crecv(bytes, bufsize)
diff --git a/vlib/rand/random_numbers_test.v b/vlib/rand/random_numbers_test.v
index bcebc2b237..fde6b0c576 100644
--- a/vlib/rand/random_numbers_test.v
+++ b/vlib/rand/random_numbers_test.v
@@ -26,7 +26,7 @@ fn test_rand_r_seed_update() {
 	seed := 10
 	for _ in 0 .. rnd_count {
 		prev_seed := seed
-		_ := rand.rand_r(&seed)
+		_ = rand.rand_r(&seed)
 		assert prev_seed != seed
 	}
 }
diff --git a/vlib/time/parse_test.v b/vlib/time/parse_test.v
index 4e2e184d79..e0df77f6aa 100644
--- a/vlib/time/parse_test.v
+++ b/vlib/time/parse_test.v
@@ -12,7 +12,7 @@ fn test_parse() {
 
 fn test_parse_invalid() {
 	s := 'Invalid time string'
-	_ := time.parse(s) or {
+	time.parse(s) or {
 		assert true
 		return
 	}
@@ -38,7 +38,7 @@ fn test_parse_rfc2822() {
 
 fn test_parse_rfc2822_invalid() {
 	s3 := 'Thu 12 Foo 2019 06:07:45 +0800'
-	_ := time.parse_rfc2822(s3) or {
+	time.parse_rfc2822(s3) or {
 		assert true
 		return
 	}
@@ -71,4 +71,4 @@ fn test_rfc8601_parse_cest() {
 	assert t.minute == 38
 	assert t.second == 6
 	assert t.microsecond == 15959
-}
\ No newline at end of file
+}
diff --git a/vlib/v/ast/ast.v b/vlib/v/ast/ast.v
index 4bab48d058..49eafd615f 100644
--- a/vlib/v/ast/ast.v
+++ b/vlib/v/ast/ast.v
@@ -801,14 +801,6 @@ pub fn expr_is_blank_ident(expr Expr) bool {
 	}
 }
 
-[inline]
-pub fn expr_is_call(expr Expr) bool {
-	return match expr {
-		CallExpr { true }
-		else { false }
-	}
-}
-
 pub fn (expr Expr) position() token.Position {
 	// all uncommented have to be implemented
 	match mut expr {
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index b932cfe411..7c0c8004ff 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -668,25 +668,36 @@ fn (mut c Checker) assign_expr(mut assign_expr ast.AssignExpr) {
 	c.expected_type = table.void_type
 	left_type := c.unwrap_generic(c.expr(assign_expr.left))
 	c.expected_type = left_type
+	if ast.expr_is_blank_ident(assign_expr.left) {
+		c.expected_type = table.Type(0)
+	}
 	assign_expr.left_type = left_type
 	// println('setting exp type to $c.expected_type $t.name')
 	right_type := c.check_expr_opt_call(assign_expr.val, c.unwrap_generic(c.expr(assign_expr.val)))
 	assign_expr.right_type = right_type
 	right := c.table.get_type_symbol(right_type)
 	left := c.table.get_type_symbol(left_type)
-	if ast.expr_is_blank_ident(assign_expr.left) {
-		return
+	match assign_expr.left {
+		ast.Ident {
+			if it.kind == .blank_ident {
+				if assign_expr.op != .assign {
+
+					c.error('cannot modify blank `_` variable', it.pos)
+				}
+				return
+			}
+		}
+		ast.PrefixExpr {
+			// Do now allow `*x = y` outside `unsafe`
+			if it.op == .mul && !c.inside_unsafe {
+				c.error('modifying variables via deferencing can only be done in `unsafe` blocks',
+					assign_expr.pos)
+			}
+		}
+		else {}
 	}
 	// Make sure the variable is mutable
 	c.fail_if_immutable(assign_expr.left)
-	// Do now allow `*x = y` outside `unsafe`
-	if assign_expr.left is ast.PrefixExpr {
-		p := assign_expr.left as ast.PrefixExpr
-		if p.op == .mul && !c.inside_unsafe {
-			c.error('modifying variables via deferencing can only be done in `unsafe` blocks',
-				assign_expr.pos)
-		}
-	}
 	// Single side check
 	match assign_expr.op {
 		.assign {} // No need to do single side check for =. But here put it first for speed.
@@ -1318,7 +1329,7 @@ pub fn (mut c Checker) assign_stmt(mut assign_stmt ast.AssignStmt) {
 	right_first := assign_stmt.right[0]
 	mut right_len := assign_stmt.right.len
 	if right_first is ast.CallExpr || right_first is ast.IfExpr || right_first is ast.MatchExpr {
-		right_type0 := c.expr(assign_stmt.right[0])
+		right_type0 := c.expr(right_first)
 		assign_stmt.right_types = [right_type0]
 		right_type_sym0 := c.table.get_type_symbol(right_type0)
 		if right_type0 == table.void_type {
@@ -1332,12 +1343,11 @@ pub fn (mut c Checker) assign_stmt(mut assign_stmt ast.AssignStmt) {
 				call_expr := assign_stmt.right[0] as ast.CallExpr
 				c.error('assignment mismatch: $assign_stmt.left.len variable(s) but `${call_expr.name}()` returns $right_len value(s)',
 					assign_stmt.pos)
-				return
 			} else {
 				c.error('assignment mismatch: $assign_stmt.left.len variable(s) $right_len value(s)',
 					assign_stmt.pos)
-				return
 			}
+			return
 		}
 	} else if assign_stmt.left.len != right_len {
 		c.error('assignment mismatch: $assign_stmt.left.len variable(s) $assign_stmt.right.len value(s)',
@@ -1354,20 +1364,19 @@ pub fn (mut c Checker) assign_stmt(mut assign_stmt ast.AssignStmt) {
 			c.check_expr_opt_call(assign_stmt.right[i], assign_stmt.right_types[i])
 		}
 		mut val_type := assign_stmt.right_types[i]
-		// check variable name for beginning with capital letter 'Abc'
-		is_decl := assign_stmt.op == .decl_assign
-		if is_decl && ident.name != '_' {
-			c.check_valid_snake_case(ident.name, 'variable name', ident.pos)
-		}
-		if assign_stmt.op == .decl_assign {
-			val_type = c.table.mktyp(val_type)
-		}
 		mut ident_var_info := ident.var_info()
-		if assign_stmt.op == .assign {
+		is_decl := assign_stmt.op == .decl_assign
+		if is_decl {
+			if ident.kind != .blank_ident {
+				// check variable name for beginning with capital letter 'Abc'
+				c.check_valid_snake_case(ident.name, 'variable name', ident.pos)
+			}
+			val_type = c.table.mktyp(val_type)
+		} else {
 			c.fail_if_immutable(ident)
 			var_type := c.expr(ident)
 			assign_stmt.left_types << var_type
-			if !c.check_types(val_type, var_type) {
+			if ident.kind != .blank_ident && !c.check_types(val_type, var_type) {
 				val_type_sym := c.table.get_type_symbol(val_type)
 				var_type_sym := c.table.get_type_symbol(var_type)
 				c.error('assign stmt: cannot use `$val_type_sym.name` as `$var_type_sym.name`',
diff --git a/vlib/v/checker/tests/blank_modify.out b/vlib/v/checker/tests/blank_modify.out
new file mode 100644
index 0000000000..12b7cc9552
--- /dev/null
+++ b/vlib/v/checker/tests/blank_modify.out
@@ -0,0 +1,5 @@
+vlib/v/checker/tests/blank_modify.v:2:2: error: cannot modify blank `_` variable
+    1 | fn main() {
+    2 |     _ += 1
+      |     ^
+    3 | }
diff --git a/vlib/v/checker/tests/blank_modify.vv b/vlib/v/checker/tests/blank_modify.vv
new file mode 100644
index 0000000000..0a22021974
--- /dev/null
+++ b/vlib/v/checker/tests/blank_modify.vv
@@ -0,0 +1,3 @@
+fn main() {
+	_ += 1
+}
diff --git a/vlib/v/checker/tests/if_expr_last_stmt.out b/vlib/v/checker/tests/if_expr_last_stmt.out
index ab8ad293eb..f51ffdd5f9 100644
--- a/vlib/v/checker/tests/if_expr_last_stmt.out
+++ b/vlib/v/checker/tests/if_expr_last_stmt.out
@@ -1,5 +1,5 @@
 vlib/v/checker/tests/if_expr_last_stmt.v:4:7: error: `if` expression requires an expression as the last statement of every branch
-    2 |     _ := if true {
+    2 |     _ = if true {
     3 |         1
     4 |     } else if false {
       |       ~~~~~~~~~~~~~
diff --git a/vlib/v/checker/tests/if_expr_last_stmt.vv b/vlib/v/checker/tests/if_expr_last_stmt.vv
index beecb65c0c..eb5dd0c71d 100644
--- a/vlib/v/checker/tests/if_expr_last_stmt.vv
+++ b/vlib/v/checker/tests/if_expr_last_stmt.vv
@@ -1,5 +1,5 @@
 fn main() {
-    _ := if true {
+    _ = if true {
         1
     } else if false {
     } else {
diff --git a/vlib/v/checker/tests/if_expr_no_else.out b/vlib/v/checker/tests/if_expr_no_else.out
index 17d5ad0ce3..c4d3306ca5 100644
--- a/vlib/v/checker/tests/if_expr_no_else.out
+++ b/vlib/v/checker/tests/if_expr_no_else.out
@@ -1,5 +1,5 @@
-vlib/v/checker/tests/if_expr_no_else.v:2:10: error: `if` expression needs `else` clause
+vlib/v/checker/tests/if_expr_no_else.v:2:9: error: `if` expression needs `else` clause
     1 | fn main() {
-    2 |     _ := if true { 1 }
-      |          ~~
+    2 |     _ = if true { 1 }
+      |         ~~
     3 | }
diff --git a/vlib/v/checker/tests/if_expr_no_else.vv b/vlib/v/checker/tests/if_expr_no_else.vv
index d3e5144888..d416cc9457 100644
--- a/vlib/v/checker/tests/if_expr_no_else.vv
+++ b/vlib/v/checker/tests/if_expr_no_else.vv
@@ -1,3 +1,3 @@
 fn main() {
-    _ := if true { 1 }
+    _ = if true { 1 }
 }
diff --git a/vlib/v/checker/tests/incorrect_name_variable.out b/vlib/v/checker/tests/incorrect_name_variable.out
index 87d31f561e..e4e7a1da47 100644
--- a/vlib/v/checker/tests/incorrect_name_variable.out
+++ b/vlib/v/checker/tests/incorrect_name_variable.out
@@ -2,5 +2,5 @@ vlib/v/checker/tests/incorrect_name_variable.v:2:2: error: variable name `_abc`
     1 | fn main() {
     2 |     _abc := 1
       |     ~~~~
-    3 |     _ := _abc
+    3 |     _ = _abc
     4 | }
\ No newline at end of file
diff --git a/vlib/v/checker/tests/incorrect_name_variable.vv b/vlib/v/checker/tests/incorrect_name_variable.vv
index dbbb549aeb..d4d42956e9 100644
--- a/vlib/v/checker/tests/incorrect_name_variable.vv
+++ b/vlib/v/checker/tests/incorrect_name_variable.vv
@@ -1,4 +1,4 @@
 fn main() {
 	_abc := 1
-	_ := _abc
+	_ = _abc
 }
diff --git a/vlib/v/checker/tests/match_expr_else.vv b/vlib/v/checker/tests/match_expr_else.vv
index fff7be0253..af97dcf3da 100644
--- a/vlib/v/checker/tests/match_expr_else.vv
+++ b/vlib/v/checker/tests/match_expr_else.vv
@@ -10,7 +10,7 @@ fn main() {
 			'string'
 		}
 	}
-	_ := match x {
+	_ = match x {
 		int {
 			'int'
 		}
@@ -24,7 +24,7 @@ fn main() {
 			'else'
 		}
 	}
-	_ := match x {
+	_ = match x {
 		int {
 			'int'
 		}
diff --git a/vlib/v/checker/tests/no_interface_instantiation_a.out b/vlib/v/checker/tests/no_interface_instantiation_a.out
index 2efdfb9dc8..0f553ee644 100644
--- a/vlib/v/checker/tests/no_interface_instantiation_a.out
+++ b/vlib/v/checker/tests/no_interface_instantiation_a.out
@@ -1,6 +1,6 @@
-vlib/v/checker/tests/no_interface_instantiation_a.v:4:10: error: cannot instantiate interface `Speaker`
+vlib/v/checker/tests/no_interface_instantiation_a.v:4:9: error: cannot instantiate interface `Speaker`
     2 |
     3 | fn main() {
-    4 |     _ := Speaker{}
-      |          ~~~~~~~~~
+    4 |     _ = Speaker{}
+      |         ~~~~~~~~~
     5 | }
\ No newline at end of file
diff --git a/vlib/v/checker/tests/no_interface_instantiation_a.vv b/vlib/v/checker/tests/no_interface_instantiation_a.vv
index 52484b68ec..1d98644259 100644
--- a/vlib/v/checker/tests/no_interface_instantiation_a.vv
+++ b/vlib/v/checker/tests/no_interface_instantiation_a.vv
@@ -1,5 +1,5 @@
 interface Speaker {}
 
 fn main() {
-    _ := Speaker{}
+    _ = Speaker{}
 }
diff --git a/vlib/v/checker/tests/selector_expr_assign.out b/vlib/v/checker/tests/selector_expr_assign.out
new file mode 100644
index 0000000000..ee7d7a9b7c
--- /dev/null
+++ b/vlib/v/checker/tests/selector_expr_assign.out
@@ -0,0 +1,6 @@
+vlib/v/checker/tests/selector_expr_assign.v:7:6: error: struct fields can only be declared during the initialization
+    5 | fn main() {
+    6 |     abc := Abc{}
+    7 |     abc.a := 2
+      |         ^
+    8 | }
diff --git a/vlib/v/checker/tests/selector_expr_assign.vv b/vlib/v/checker/tests/selector_expr_assign.vv
new file mode 100644
index 0000000000..024c869880
--- /dev/null
+++ b/vlib/v/checker/tests/selector_expr_assign.vv
@@ -0,0 +1,8 @@
+struct Abc {
+	a int
+}
+
+fn main() {
+	abc := Abc{}
+	abc.a := 2
+}
diff --git a/vlib/v/checker/tests/struct_unknown_field.out b/vlib/v/checker/tests/struct_unknown_field.out
index 4b2893ef4f..8009084882 100644
--- a/vlib/v/checker/tests/struct_unknown_field.out
+++ b/vlib/v/checker/tests/struct_unknown_field.out
@@ -1,7 +1,7 @@
-vlib/v/checker/tests/struct_unknown_field.v:8:9: error: unknown field `bar` in struct literal of type `Test`
+vlib/v/checker/tests/struct_unknown_field.v:8:3: error: unknown field `bar` in struct literal of type `Test`
     6 |     t := Test{
     7 |         foo: true
     8 |         bar: false
       |         ~~~~~~~~~~
     9 |     }
-   10 |      _ = t
+   10 |     _ = t
diff --git a/vlib/v/checker/tests/struct_unknown_field.vv b/vlib/v/checker/tests/struct_unknown_field.vv
index e4ec496630..018bcefc87 100644
--- a/vlib/v/checker/tests/struct_unknown_field.vv
+++ b/vlib/v/checker/tests/struct_unknown_field.vv
@@ -4,8 +4,8 @@ struct Test {
 
 fn main() {
 	t := Test{
-        foo: true
-        bar: false
-    }
-	 _ = t
+		foo: true
+		bar: false
+	}
+	_ = t
 }
diff --git a/vlib/v/checker/tests/unexpected_or.out b/vlib/v/checker/tests/unexpected_or.out
index 050750c9bf..f02adcb6b5 100644
--- a/vlib/v/checker/tests/unexpected_or.out
+++ b/vlib/v/checker/tests/unexpected_or.out
@@ -1,6 +1,6 @@
-vlib/v/checker/tests/unexpected_or.v:6:7: error: unexpected `or` block, the function `ret_zero` does not return an optional
+vlib/v/checker/tests/unexpected_or.v:6:6: error: unexpected `or` block, the function `ret_zero` does not return an optional
     4 |
     5 | fn main() {
-    6 |     _ := ret_zero() or { 1 }
-      |          ~~~~~~~~~~
+    6 |     _ = ret_zero() or { 1 }
+      |         ~~~~~~~~~~
     7 | }
diff --git a/vlib/v/checker/tests/unexpected_or.vv b/vlib/v/checker/tests/unexpected_or.vv
index 2ced3c9309..48a86968ec 100644
--- a/vlib/v/checker/tests/unexpected_or.vv
+++ b/vlib/v/checker/tests/unexpected_or.vv
@@ -3,5 +3,5 @@ fn ret_zero() int {
 }
 
 fn main() {
-	_ := ret_zero() or { 1 }
+	_ = ret_zero() or { 1 }
 }
diff --git a/vlib/v/checker/tests/void_fn_as_value.out b/vlib/v/checker/tests/void_fn_as_value.out
index f612c8abef..ce188c700b 100644
--- a/vlib/v/checker/tests/void_fn_as_value.out
+++ b/vlib/v/checker/tests/void_fn_as_value.out
@@ -1,7 +1,7 @@
-vlib/v/checker/tests/void_fn_as_value.v:5:8: error: unknown function: x
+vlib/v/checker/tests/void_fn_as_value.v:5:7: error: unknown function: x
     3 | fn main() {
-    4 |   mut a := 'aa'
-    5 |   a += x('a','b')
-      |        ~~~~~~~~~~
-    6 |   mut b := 'abcdef'
-    7 |   _ = b
+    4 |     mut a := 'aa'
+    5 |     a += x('a','b')
+      |          ~~~~~~~~~~
+    6 |     mut b := 'abcdef'
+    7 |     _ = b
diff --git a/vlib/v/checker/tests/void_fn_as_value.vv b/vlib/v/checker/tests/void_fn_as_value.vv
index 4d6f97dc39..1ab1394321 100644
--- a/vlib/v/checker/tests/void_fn_as_value.vv
+++ b/vlib/v/checker/tests/void_fn_as_value.vv
@@ -1,8 +1,8 @@
 module main
 
 fn main() {
-  mut a := 'aa'
-  a += x('a','b')
-  mut b := 'abcdef'
-  _ = b
+	mut a := 'aa'
+	a += x('a','b')
+	mut b := 'abcdef'
+	_ = b
 }
diff --git a/vlib/v/checker/tests/void_optional_err.vv b/vlib/v/checker/tests/void_optional_err.vv
index ca812cc628..136e6e5adc 100644
--- a/vlib/v/checker/tests/void_optional_err.vv
+++ b/vlib/v/checker/tests/void_optional_err.vv
@@ -3,5 +3,5 @@ fn ret_void() ?void {
 }
 
 fn main() {
-	_ := ret_void() or { panic('$err') }
+	_ = ret_void() or { panic('$err') }
 }
diff --git a/vlib/v/doc/doc.v b/vlib/v/doc/doc.v
index 2bfcc6203c..3b6176cbe2 100644
--- a/vlib/v/doc/doc.v
+++ b/vlib/v/doc/doc.v
@@ -341,7 +341,7 @@ pub fn generate(input_path string, pub_only, with_comments bool) ?Doc {
 	mut doc := new(input_path)
 	doc.pub_only = pub_only
 	doc.with_comments = with_comments
-	_ = doc.generate() or {
+	doc.generate() or {
 		return error(err)
 	}
 	return doc
diff --git a/vlib/v/gen/js/tests/js.v b/vlib/v/gen/js/tests/js.v
index 10795dfe83..c9a5f14281 100644
--- a/vlib/v/gen/js/tests/js.v
+++ b/vlib/v/gen/js/tests/js.v
@@ -48,7 +48,7 @@ fn main() {
 
     v := "done"
     {
-        _ := "block"
+        _ = "block"
     }
 
     pos := POSITION.go_back
diff --git a/vlib/v/parser/assign.v b/vlib/v/parser/assign.v
index 6917b819a3..46d77827de 100644
--- a/vlib/v/parser/assign.v
+++ b/vlib/v/parser/assign.v
@@ -92,8 +92,7 @@ fn (mut p Parser) partial_assign_stmt(known_lhs []ast.Ident) ast.Stmt {
 		}
 	}
 	for i, ident in idents {
-		known_var := p.scope.known_var(ident.name)
-		if !is_decl && !known_var {
+		if !is_decl && ident.kind != .blank_ident && !p.scope.known_var(ident.name) {
 			p.error('unknown variable `$ident.name`')
 		}
 		if is_decl && ident.kind != .blank_ident {
@@ -132,12 +131,9 @@ pub fn (mut p Parser) assign_expr(left ast.Expr) ast.AssignExpr {
 	pos := p.tok.position()
 	p.next()
 	val := p.expr(0)
-	match left {
-		ast.IndexExpr {
-			// it.mark_as_setter()
-			it.is_setter = true
-		}
-		else {}
+	if left is ast.IndexExpr {
+		mut index_expr := left as ast.IndexExpr
+		index_expr.is_setter = true
 	}
 	node := ast.AssignExpr{
 		left: left
diff --git a/vlib/v/parser/parser.v b/vlib/v/parser/parser.v
index 3ed4e47955..7e6485ca9b 100644
--- a/vlib/v/parser/parser.v
+++ b/vlib/v/parser/parser.v
@@ -729,7 +729,17 @@ fn (mut p Parser) parse_multi_expr() ast.Stmt {
 	if p.tok.kind == .decl_assign || (p.tok.kind == .assign && collected.len > 1) {
 		mut idents := []ast.Ident{}
 		for c in collected {
-			idents << c as ast.Ident
+			match c {
+				ast.Ident {
+					idents << it
+				}
+				ast.SelectorExpr {
+					p.error_with_pos('struct fields can only be declared during the initialization', it.pos)
+				}
+				else {
+					p.error_with_pos('unexpected `${typeof(c)}`', c.position())
+				}
+			}
 		}
 		return p.partial_assign_stmt(idents)
 	} else if p.tok.kind.is_assign() {
@@ -789,19 +799,18 @@ pub fn (mut p Parser) parse_ident(language table.Language) ast.Ident {
 		if p.expr_mod.len > 0 {
 			name = '${p.expr_mod}.$name'
 		}
-		mut ident := ast.Ident{
+		return ast.Ident{
 			kind: .unresolved
 			name: name
 			language: language
 			mod: p.mod
 			pos: pos
-		}
-		ident.is_mut = is_mut
-		ident.info = ast.IdentVar{
 			is_mut: is_mut
-			is_static: is_static
+			info: ast.IdentVar{
+				is_mut: is_mut
+				is_static: is_static
+			}
 		}
-		return ident
 	} else {
 		p.error('unexpected token `$p.tok.lit`')
 	}
diff --git a/vlib/v/table/table.v b/vlib/v/table/table.v
index e10aec8f01..247ef093a2 100644
--- a/vlib/v/table/table.v
+++ b/vlib/v/table/table.v
@@ -264,7 +264,7 @@ pub fn (mut t Table) register_type_symbol(typ TypeSymbol) int {
 }
 
 pub fn (t &Table) known_type(name string) bool {
-	_ = t.find_type(name) or {
+	t.find_type(name) or {
 		return false
 	}
 	return true
diff --git a/vlib/v/tests/array_init_test.v b/vlib/v/tests/array_init_test.v
index 4209f7651c..d72f6cc5f8 100644
--- a/vlib/v/tests/array_init_test.v
+++ b/vlib/v/tests/array_init_test.v
@@ -66,7 +66,7 @@ fn test_array_int_full_options() {
 	assert a.str() == "[0, 0]"
 
 	b := []int{len: 10, cap: 100, init: 1} // this creates an array with 10 one and initial capacity 100 elements, value given
-	_ := b.clone() // discard result variable, sample
+	_ = b.clone() // discard result variable, sample
 	println('array b: length: ${b.len}, capacity: ${b.cap}, content: $b')
 	assert b.len == 10
 	assert b.cap == 100
@@ -74,7 +74,7 @@ fn test_array_int_full_options() {
 	assert b.str() == "[1, 1, 1, 1, 1, 1, 1, 1, 1, 1]"
 
 	mut c := []int{len: 2, cap: 10, init: 1} // this creates an array with 2 one and initial capacity 10 elements, value given
-	_ := c.clone() // discard result variable, sample
+	_ = c.clone() // discard result variable, sample
 	println('array c: length: ${c.len}, capacity: ${c.cap}, content: $c')
 	assert c.len == 2
 	assert c.cap == 10
@@ -109,7 +109,7 @@ fn test_array_string_full_options() {
 	assert a.str() == "['', '']"
 
 	b := []string{len: 10, cap: 100, init: 'b'} // this creates an array with 10 'b', initial capacity 100 elements, value given
-	_ := b.clone() // discard result variable, sample
+	_ = b.clone() // discard result variable, sample
 	println('array b: length: ${b.len}, capacity: ${b.cap}') // ok
 	println('array b: length: ${b.len}, capacity: ${b.cap}, content: $b')
 	assert b.len == 10
@@ -118,7 +118,7 @@ fn test_array_string_full_options() {
 	assert b.str() == "['b', 'b', 'b', 'b', 'b', 'b', 'b', 'b', 'b', 'b']"
 
 	mut c := []string{len: 2, cap: 10, init: 'c'} // this creates an array with 2 'c' and initial capacity 10 elements, value given
-	_ := c.clone() // discard result variable, sample
+	_ = c.clone() // discard result variable, sample
 	println('array c: length: ${c.len}, capacity: ${c.cap}, content: $c')
 	assert c.len == 2
 	assert c.cap == 10
diff --git a/vlib/v/tests/fn_high_test.v b/vlib/v/tests/fn_high_test.v
index 8f70aa4982..0cbdb4db80 100644
--- a/vlib/v/tests/fn_high_test.v
+++ b/vlib/v/tests/fn_high_test.v
@@ -21,7 +21,7 @@ fn high_fn_multi_return(a int, b fn (c []int, d []string) ([]int, []string)) {
 }
 
 fn high_fn_return_single_anon() (fn(int)f32) {
-	_ := 1
+	_ = 1
 	correct := fn(n int)f32 {
 		return f32(n * n)
 	}
@@ -29,7 +29,7 @@ fn high_fn_return_single_anon() (fn(int)f32) {
 }
 fn high_fn_return_multi_anons() (fn(int)f32, fn(int)string) {
 	// parsing trap
-	_ := fn(n int)byte {
+	_ = fn(n int)byte {
 		return 0x00
 	}
 	correct_second := fn(n int)string {
@@ -39,7 +39,7 @@ fn high_fn_return_multi_anons() (fn(int)f32, fn(int)string) {
 		return f32(n * n)
 	}
 	// parsing trap
-	_ := fn(n int)[]int {
+	_ = fn(n int)[]int {
 		return [n]
 	}
 	return correct_first, correct_second
diff --git a/vlib/v/tests/vmod_parser_test.v b/vlib/v/tests/vmod_parser_test.v
index 3a4a85b846..c7168297c3 100644
--- a/vlib/v/tests/vmod_parser_test.v
+++ b/vlib/v/tests/vmod_parser_test.v
@@ -35,7 +35,7 @@ fn test_decode() {
 	assert data.license == 'GPL-2.0'
 	assert data.dependencies[0] == 'hello'
 	assert data.unknown['test'][0] == 'foo'
-	_ := vmod.decode('') or {
+	vmod.decode('') or {
 		assert err == 'vmod: no content.'
 		exit(0)
 	}