diff --git a/cmd/tools/vfmt.v b/cmd/tools/vfmt.v
index d9b75563ce..9bf4fae4df 100644
--- a/cmd/tools/vfmt.v
+++ b/cmd/tools/vfmt.v
@@ -235,7 +235,7 @@ fn find_working_diff_command() ?string {
 	return error('no working diff command found')
 }
 
-pub fn (f FormatOptions) str() string {
+fn (f FormatOptions) str() string {
 	return 'FormatOptions{ is_l: $f.is_l' + ' is_w: $f.is_w' + ' is_diff: $f.is_diff' + ' is_verbose: $f.is_verbose' +
 		' is_all: $f.is_all' + ' is_worker: $f.is_worker' + ' is_debug: $f.is_debug' + ' }'
 }
diff --git a/vlib/v/ast/ast.v b/vlib/v/ast/ast.v
index 2c1c027167..a94583c2ec 100644
--- a/vlib/v/ast/ast.v
+++ b/vlib/v/ast/ast.v
@@ -3,10 +3,8 @@
 // that can be found in the LICENSE file.
 module ast
 
-import (
-	v.token
-	v.table
-)
+import v.token
+import v.table
 
 pub type TypeDecl = AliasTypeDecl | SumTypeDecl | FnTypeDecl
 
@@ -95,9 +93,9 @@ mut:
 // module declaration
 pub struct Module {
 pub:
-	name string
-	path string
-	expr Expr
+	name       string
+	path       string
+	expr       Expr
 	is_skipped bool // module main can be skipped in single file programs
 }
 
@@ -162,7 +160,7 @@ pub struct StructInitField {
 pub:
 	name          string
 	expr          Expr
-	pos			  token.Position
+	pos           token.Position
 mut:
 	typ           table.Type
 	expected_type table.Type
@@ -189,7 +187,7 @@ pub struct AnonFn {
 pub:
 	decl FnDecl
 mut:
-	typ table.Type
+	typ  table.Type
 }
 
 pub struct FnDecl {
@@ -228,7 +226,7 @@ mut:
 	args               []CallArg
 	expected_arg_types []table.Type
 	is_c               bool
-	is_js			   bool
+	is_js              bool
 	or_block           OrExpr
 	left_type          table.Type // type of `user`
 	receiver_type      table.Type // User
@@ -326,7 +324,7 @@ pub:
 	tok_kind token.Kind
 	mod      string
 	pos      token.Position
-	is_mut bool
+	is_mut   bool
 mut:
 	name     string
 	kind     IdentKind
@@ -537,11 +535,11 @@ pub struct EnumField {
 
 pub struct EnumDecl {
 pub:
-	name          string
-	is_pub        bool
-	fields        []EnumField
-	// vals          []string
+	name   string
+	is_pub bool
+	fields []EnumField
 	// default_exprs []Expr
+	pos    token.Position
 }
 
 pub struct AliasTypeDecl {
@@ -549,6 +547,7 @@ pub:
 	name        string
 	is_pub      bool
 	parent_type table.Type
+	pos         token.Position
 }
 
 pub struct SumTypeDecl {
@@ -556,6 +555,7 @@ pub:
 	name      string
 	is_pub    bool
 	sub_types []table.Type
+	pos       token.Position
 }
 
 pub struct FnTypeDecl {
@@ -563,6 +563,7 @@ pub:
 	name   string
 	is_pub bool
 	typ    table.Type
+	pos    token.Position
 }
 
 // TODO: handle this differently
@@ -720,30 +721,22 @@ pub:
 [inline]
 pub fn expr_is_blank_ident(expr Expr) bool {
 	match expr {
-		Ident {
-			return it.kind == .blank_ident
-		}
-		else {
-			return false
-		}
+		Ident { return it.kind == .blank_ident }
+		else { return false }
 	}
 }
 
 [inline]
 pub fn expr_is_call(expr Expr) bool {
 	return match expr {
-		CallExpr {
-			true
-		}
-		else {
-			false
-		}
+		CallExpr { true }
+		else { false }
 	}
 }
 
 fn (expr Expr) position() token.Position {
 	// all uncommented have to be implemented
-	match mut expr {
+	match var expr {
 		ArrayInit {
 			return it.pos
 		}
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 6a851e2e4a..63eceba190 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -66,11 +66,8 @@ pub fn (c mut Checker) check_files(ast_files []ast.File) {
 	for file in ast_files {
 		c.check(file)
 		if file.mod.name == 'main' {
-			if fn_decl := get_main_fn_decl(file) {
+			if c.check_file_in_main(file) {
 				has_main_fn = true
-				if fn_decl.is_pub {
-					c.error('function `main` cannot be declared public', fn_decl.pos)
-				}
 			}
 		}
 	}
@@ -87,16 +84,71 @@ pub fn (c mut Checker) check_files(ast_files []ast.File) {
 	}
 }
 
-fn get_main_fn_decl(file ast.File) ?ast.FnDecl {
+const (
+	no_pub_in_main_warning = 'in module main cannot be declared public'
+)
+
+// do checks specific to files in main module
+// returns `true` if a main function is in the file
+fn (c mut Checker) check_file_in_main(file ast.File) bool {
+	mut has_main_fn := false
 	for stmt in file.stmts {
-		if stmt is ast.FnDecl {
-			fn_decl := stmt as ast.FnDecl
-			if fn_decl.name == 'main' {
-				return fn_decl
+		match stmt {
+			ast.ConstDecl {
+				if it.is_pub {
+					c.warn('const $no_pub_in_main_warning', it.pos)
+				}
 			}
+			ast.ConstField {
+				if it.is_pub {
+					c.warn('const field `$it.name` $no_pub_in_main_warning', it.pos)
+				}
+			}
+			ast.EnumDecl {
+				if it.is_pub {
+					c.warn('enum `$it.name` $no_pub_in_main_warning', it.pos)
+				}
+			}
+			ast.FnDecl {
+				if it.name == 'main' {
+					has_main_fn = true
+					if it.is_pub {
+						c.error('function `main` cannot be declared public', it.pos)
+					}
+				} else {
+					if it.is_pub {
+						c.warn('function `$it.name` $no_pub_in_main_warning', it.pos)
+					}
+				}
+			}
+			ast.StructDecl {
+				if it.is_pub {
+					c.warn('struct `$it.name` $no_pub_in_main_warning', it.pos)
+				}
+			}
+			ast.TypeDecl {
+				type_decl := stmt as ast.TypeDecl
+				if type_decl is ast.AliasTypeDecl {
+					alias_decl := type_decl as ast.AliasTypeDecl
+					if alias_decl.is_pub {
+						c.warn('type alias `$alias_decl.name` $no_pub_in_main_warning', alias_decl.pos)
+					}
+				} else if type_decl is ast.SumTypeDecl {
+					sum_decl := type_decl as ast.SumTypeDecl
+					if sum_decl.is_pub {
+						c.warn('sum type `$sum_decl.name` $no_pub_in_main_warning', sum_decl.pos)
+					}
+				} else if type_decl is ast.FnTypeDecl {
+					fn_decl := type_decl as ast.FnTypeDecl
+					if fn_decl.is_pub {
+						c.warn('type alias `$fn_decl.name` $no_pub_in_main_warning', fn_decl.pos)
+					}
+				}
+			}
+			else {}
 		}
 	}
-	return none
+	return has_main_fn
 }
 
 pub fn (c mut Checker) struct_decl(decl ast.StructDecl) {
diff --git a/vlib/v/checker/tests/inout/checker_error_test.v b/vlib/v/checker/tests/inout/checker_error_test.v
index a7c3350515..d565f86420 100644
--- a/vlib/v/checker/tests/inout/checker_error_test.v
+++ b/vlib/v/checker/tests/inout/checker_error_test.v
@@ -24,7 +24,8 @@ fn test_all() {
 		os.cp(path, program) or {
 			panic(err)
 		}
-		res := os.exec('$vexe $program') or {
+		// -prod so that warn are errors
+		res := os.exec('$vexe -prod $program') or {
 			panic(err)
 		}
 		mut expected := os.read_file(program.replace('.v', '') + '.out') or {
diff --git a/vlib/v/checker/tests/inout/no_pub_in_main.out b/vlib/v/checker/tests/inout/no_pub_in_main.out
new file mode 100644
index 0000000000..bba28e48db
--- /dev/null
+++ b/vlib/v/checker/tests/inout/no_pub_in_main.out
@@ -0,0 +1,49 @@
+vlib/v/checker/tests/inout/no_pub_in_main.v:3:1: error: type alias `Integer` in module main cannot be declared public
+    1| module main
+    2|
+    3| pub type Integer = int
+       ~~~~~~~~~~~~~~~~
+    4|
+    5| pub type Float = f32 | f64
+vlib/v/checker/tests/inout/no_pub_in_main.v:5:1: error: sum type `Float` in module main cannot be declared public
+    3| pub type Integer = int
+    4|
+    5| pub type Float = f32 | f64
+       ~~~~~~~~~~~~~~
+    6|
+    7| // Buggy ATM
+vlib/v/checker/tests/inout/no_pub_in_main.v:10:1: error: enum `Color` in module main cannot be declared public
+    8| // pub type Fn = fn () int
+    9|
+   10| pub enum Color {
+       ~~~~~~~~~~~~~~
+   11|     red
+   12|     green
+vlib/v/checker/tests/inout/no_pub_in_main.v:16:1: error: const in module main cannot be declared public
+   14| }
+   15|
+   16| pub const (
+       ~~~~~~~~~
+   17|     w = 'world'
+   18| )
+vlib/v/checker/tests/inout/no_pub_in_main.v:20:1: error: function `my_fn` in module main cannot be declared public
+   18| )
+   19|
+   20| pub fn my_fn() int {
+       ~~~~~~~~~~~~~~~~~~
+   21|     return 1
+   22| }
+vlib/v/checker/tests/inout/no_pub_in_main.v:24:1: error: function `main` cannot be declared public
+   22| }
+   23|
+   24| pub fn main() {
+       ~~~~~~~~~~~~~
+   25|     println('main')
+   26| }
+vlib/v/checker/tests/inout/no_pub_in_main.v:28:1: error: struct `MyStruct` in module main cannot be declared public
+   26| }
+   27|
+   28| pub struct MyStruct {
+       ~~~~~~~~~~~~~~~~~~~
+   29|     field int
+   30| }
diff --git a/vlib/v/checker/tests/inout/no_pub_in_main.vv b/vlib/v/checker/tests/inout/no_pub_in_main.vv
new file mode 100644
index 0000000000..76d6ee0114
--- /dev/null
+++ b/vlib/v/checker/tests/inout/no_pub_in_main.vv
@@ -0,0 +1,30 @@
+module main
+
+pub type Integer = int
+
+pub type Float = f32 | f64
+
+// Buggy ATM
+// pub type Fn = fn () int
+
+pub enum Color {
+	red
+	green
+	blue
+}
+
+pub const (
+	w = 'world'
+)
+
+pub fn my_fn() int {
+	return 1
+}
+
+pub fn main() {
+	println('main')
+}
+
+pub struct MyStruct {
+	field int
+}
diff --git a/vlib/v/checker/tests/inout/pub_fn_main.out b/vlib/v/checker/tests/inout/pub_fn_main.out
deleted file mode 100644
index a0d7830153..0000000000
--- a/vlib/v/checker/tests/inout/pub_fn_main.out
+++ /dev/null
@@ -1,5 +0,0 @@
-vlib/v/checker/tests/inout/pub_fn_main.v:1:1: error: function `main` cannot be declared public
-    1| pub fn main() {
-       ~~~
-    2|     println('Hello world !')
-    3| }
diff --git a/vlib/v/checker/tests/inout/pub_fn_main.vv b/vlib/v/checker/tests/inout/pub_fn_main.vv
deleted file mode 100644
index 0f47c312c0..0000000000
--- a/vlib/v/checker/tests/inout/pub_fn_main.vv
+++ /dev/null
@@ -1,3 +0,0 @@
-pub fn main() {
-	println('Hello world !')
-}
diff --git a/vlib/v/parser/fn.v b/vlib/v/parser/fn.v
index 2b519216bf..f9461a2cc2 100644
--- a/vlib/v/parser/fn.v
+++ b/vlib/v/parser/fn.v
@@ -85,7 +85,7 @@ pub fn (var p Parser) call_args() []ast.CallArg {
 
 fn (var p Parser) fn_decl() ast.FnDecl {
 	// p.table.clear_vars()
-	pos := p.tok.position()
+	start_pos := p.tok.position()
 	p.open_scope()
 	is_deprecated := p.attr == 'deprecated'
 	is_pub := p.tok.kind == .key_pub
@@ -165,9 +165,11 @@ fn (var p Parser) fn_decl() ast.FnDecl {
 			typ: arg.typ
 		})
 	}
+	var end_pos := p.prev_tok.position()
 	// Return type
 	var return_type := table.void_type
 	if p.tok.kind.is_start_of_type() {
+		end_pos = p.tok.position()
 		return_type = p.parse_type()
 	}
 	// Register
@@ -229,7 +231,7 @@ fn (var p Parser) fn_decl() ast.FnDecl {
 		is_c: is_c
 		is_js: is_js
 		no_body: no_body
-		pos: pos
+		pos: start_pos.extend(end_pos)
 		is_builtin: p.builtin_mod || p.mod in util.builtin_module_parts
 	}
 }
diff --git a/vlib/v/parser/parser.v b/vlib/v/parser/parser.v
index a9c49a02e2..1d882fbf64 100644
--- a/vlib/v/parser/parser.v
+++ b/vlib/v/parser/parser.v
@@ -945,11 +945,12 @@ fn (var p Parser) import_stmt() []ast.Import {
 }
 
 fn (var p Parser) const_decl() ast.ConstDecl {
+	start_pos := p.tok.position()
 	is_pub := p.tok.kind == .key_pub
 	if is_pub {
 		p.next()
 	}
-	pos := p.tok.position()
+	end_pos := p.tok.position()
 	p.check(.key_const)
 	if p.tok.kind != .lpar {
 		p.error('consts must be grouped, e.g.\nconst (\n\ta = 1\n)')
@@ -975,7 +976,7 @@ fn (var p Parser) const_decl() ast.ConstDecl {
 	}
 	p.check(.rpar)
 	return ast.ConstDecl{
-		pos: pos
+		pos: start_pos.extend(end_pos)
 		fields: fields
 		is_pub: is_pub
 	}
@@ -1000,14 +1001,10 @@ fn (var p Parser) return_stmt() ast.Return {
 			break
 		}
 	}
-	last_pos := exprs.last().position()
+	end_pos := exprs.last().position()
 	return ast.Return{
 		exprs: exprs
-		pos: token.Position{
-			line_nr: first_pos.line_nr
-			pos: first_pos.pos
-			len: last_pos.pos - first_pos.pos + last_pos.len
-		}
+		pos: first_pos.extend(end_pos)
 	}
 }
 
@@ -1054,10 +1051,12 @@ fn (var p Parser) global_decl() ast.GlobalDecl {
 
 fn (var p Parser) enum_decl() ast.EnumDecl {
 	is_pub := p.tok.kind == .key_pub
+	start_pos := p.tok.position()
 	if is_pub {
 		p.next()
 	}
 	p.check(.key_enum)
+	end_pos := p.tok.position()
 	name := p.prepend_mod(p.check_name())
 	p.check(.lcbr)
 	var vals := []string
@@ -1101,15 +1100,19 @@ fn (var p Parser) enum_decl() ast.EnumDecl {
 		name: name
 		is_pub: is_pub
 		fields: fields
+		pos: start_pos.extend(end_pos)
 	}
 }
 
 fn (var p Parser) type_decl() ast.TypeDecl {
+	start_pos := p.tok.position()
 	is_pub := p.tok.kind == .key_pub
 	if is_pub {
 		p.next()
 	}
 	p.check(.key_type)
+	end_pos := p.tok.position()
+	decl_pos := start_pos.extend(end_pos)
 	name := p.check_name()
 	var sum_variants := []table.Type
 	if p.tok.kind == .assign {
@@ -1123,6 +1126,7 @@ fn (var p Parser) type_decl() ast.TypeDecl {
 			name: fn_name
 			is_pub: is_pub
 			typ: fn_type
+			pos: decl_pos
 		}
 	}
 	first_type := p.parse_type()	// need to parse the first type before we can check if it's `type A = X | Y`
@@ -1149,6 +1153,7 @@ fn (var p Parser) type_decl() ast.TypeDecl {
 			name: name
 			is_pub: is_pub
 			sub_types: sum_variants
+			pos: decl_pos
 		}
 	}
 	// type MyType int
@@ -1166,6 +1171,7 @@ fn (var p Parser) type_decl() ast.TypeDecl {
 		name: name
 		is_pub: is_pub
 		parent_type: parent_type
+		pos: decl_pos
 	}
 }
 
diff --git a/vlib/v/parser/struct.v b/vlib/v/parser/struct.v
index 62f19a1126..1b9efaea23 100644
--- a/vlib/v/parser/struct.v
+++ b/vlib/v/parser/struct.v
@@ -8,7 +8,7 @@ import v.table
 import v.token
 
 fn (var p Parser) struct_decl() ast.StructDecl {
-	first_pos := p.tok.position()
+	start_pos := p.tok.position()
 	is_pub := p.tok.kind == .key_pub
 	if is_pub {
 		p.next()
@@ -30,6 +30,7 @@ fn (var p Parser) struct_decl() ast.StructDecl {
 	if !is_c && !is_js && no_body {
 		p.error('`$p.tok.lit` lacks body')
 	}
+	end_pos := p.tok.position()
 	var name := p.check_name()
 	// println('struct decl $name')
 	var ast_fields := []ast.StructField
@@ -37,7 +38,6 @@ fn (var p Parser) struct_decl() ast.StructDecl {
 	var mut_pos := -1
 	var pub_pos := -1
 	var pub_mut_pos := -1
-	var last_pos := token.Position{}
 	if !no_body {
 		p.check(.lcbr)
 		for p.tok.kind != .rcbr {
@@ -113,7 +113,6 @@ fn (var p Parser) struct_decl() ast.StructDecl {
 			}
 			// println('struct field $ti.name $field_name')
 		}
-		last_pos = p.tok.position()
 		p.check(.rcbr)
 	}
 	if is_c {
@@ -145,16 +144,11 @@ fn (var p Parser) struct_decl() ast.StructDecl {
 		p.error('cannot register type `$name`, another type with this name exists')
 	}
 	p.expr_mod = ''
-	pos := token.Position{
-		line_nr: first_pos.line_nr
-		pos: first_pos.pos
-		len: last_pos.pos - first_pos.pos + last_pos.len
-	}
 	return ast.StructDecl{
 		name: name
 		is_pub: is_pub
 		fields: ast_fields
-		pos: pos
+		pos: start_pos.extend(end_pos)
 		mut_pos: mut_pos
 		pub_pos: pub_pos
 		pub_mut_pos: pub_mut_pos
diff --git a/vlib/v/token/position.v b/vlib/v/token/position.v
index ecc0272c6e..8d953a60ac 100644
--- a/vlib/v/token/position.v
+++ b/vlib/v/token/position.v
@@ -14,6 +14,13 @@ pub fn (pos Position) str() string {
 	return 'Position{ line_nr: $pos.line_nr, pos: $pos.pos, len: $pos.len }'
 }
 
+pub fn (pos Position) extend(end Position) Position {
+	return {
+		pos |
+		len: end.pos - pos.pos + end.len
+	}
+}
+
 [inline]
 pub fn (tok &Token) position() Position {
 	return Position{