checker: do now allow type name shadowing (#11401)

vlib/v/checker/checker.v

@@ -31,6 +31,8 @@ const (
 	valid_comp_not_user_defined = all_valid_comptime_idents()
 	array_builtin_methods       = ['filter', 'clone', 'repeat', 'reverse', 'map', 'slice', 'sort',
 		'contains', 'index', 'wait', 'any', 'all', 'first', 'last', 'pop']
+	reserved_type_names         = ['bool', 'i8', 'i16', 'int', 'i64', 'byte', 'u16', 'u32', 'u64',
+		'f32', 'f64', 'string', 'tune']
 	vroot_is_deprecated_message = '@VROOT is deprecated, use @VMODROOT or @VEXEROOT instead'
 )
 
@@ -4026,6 +4028,10 @@ pub fn (mut c Checker) assign_stmt(mut node ast.AssignStmt) {
 				} else {
 					if is_decl {
 						c.check_valid_snake_case(left.name, 'variable name', left.pos)
+						if left.name in checker.reserved_type_names {
+							c.error('invalid use of reserved type `$left.name` as a variable name',
+								left.pos)
+						}
 					}
 					mut ident_var_info := left.info as ast.IdentVar
 					if ident_var_info.share == .shared_t {

vlib/v/checker/tests/invalid_variable_name_err.out

@@ -0,0 +1,34 @@
+vlib/v/checker/tests/invalid_variable_name_err.vv:2:2: error: invalid use of reserved type `string` as a variable name
+    1 | fn main() {
+    2 |     string := 'hello, world'
+      |     ~~~~~~
+    3 |     println(string)
+    4 |
+vlib/v/checker/tests/invalid_variable_name_err.vv:5:2: error: invalid use of reserved type `bool` as a variable name
+    3 |     println(string)
+    4 |
+    5 |     bool := true
+      |     ~~~~
+    6 |     println(bool)
+    7 |
+vlib/v/checker/tests/invalid_variable_name_err.vv:8:2: error: invalid use of reserved type `int` as a variable name
+    6 |     println(bool)
+    7 |
+    8 |     int := 22
+      |     ~~~
+    9 |     println(int)
+   10 |
+vlib/v/checker/tests/invalid_variable_name_err.vv:11:2: error: invalid use of reserved type `u64` as a variable name
+    9 |     println(int)
+   10 |
+   11 |     u64 := 222
+      |     ~~~
+   12 |     println(u64)
+   13 |
+vlib/v/checker/tests/invalid_variable_name_err.vv:14:2: error: invalid use of reserved type `f64` as a variable name
+   12 |     println(u64)
+   13 |
+   14 |     f64 := 2.22
+      |     ~~~
+   15 |     println(f64)
+   16 | }

vlib/v/checker/tests/invalid_variable_name_err.vv

@@ -0,0 +1,16 @@
+fn main() {
+	string := 'hello, world'
+	println(string)
+
+	bool := true
+	println(bool)
+
+	int := 22
+	println(int)
+
+	u64 := 222
+	println(u64)
+
+	f64 := 2.22
+	println(f64)
+}

vlib/v/tests/reserved_keywords_array_test.v

@@ -6,8 +6,4 @@ fn test_reserved_keywords_array_and_string() {
 	assert res1 == [3, 6, 9, 12]
 	println(res2)
 	assert res2 == [3, 4]
-
-	string := 'hello'
-	println(string)
-	assert string == 'hello'
 }