checker: avoid SelectorExpr filter on Ident unless it's a generic type name (#8357)

vlib/v/checker/checker.v

@@ -2050,7 +2050,8 @@ pub fn (mut c Checker) selector_expr(mut selector_expr ast.SelectorExpr) table.T
 	match mut selector_expr.expr {
 		ast.Ident {
 			name := selector_expr.expr.name
-			valid_generic := c.cur_fn.generic_params.filter(it.name == name).len != 0
+			valid_generic := util.is_generic_type_name(name)
+				&& c.cur_fn.generic_params.filter(it.name == name).len != 0
 			if valid_generic {
 				name_type = table.Type(c.table.find_type_idx(name)).set_flag(.generic)
 			}

vlib/v/parser/fn.v

@@ -449,7 +449,7 @@ fn (mut p Parser) parse_generic_params() []ast.GenericParam {
 		if name.len > 1 {
 			p.error('generic parameter name needs to be exactly one char')
 		}
-		if is_generic_name_reserved(p.tok.lit) {
+		if !util.is_generic_type_name(p.tok.lit) {
 			p.error('`$p.tok.lit` is a reserved name and cannot be used for generics')
 		}
 		if name in param_names {
@@ -467,23 +467,9 @@ fn (mut p Parser) parse_generic_params() []ast.GenericParam {
 	return param_names.map(ast.GenericParam{it})
 }
 
-// is_valid_generic_character returns true if the character is reserved for someting else.
-fn is_generic_name_reserved(name string) bool {
-	// C is used for cinterop
-	if name == 'C' {
-		return true
-	}
-	return false
-}
-
-// is_generic_name returns true if the current token is a generic name.
-fn is_generic_name(name string) bool {
-	return name.len == 1 && name.is_capital() && !is_generic_name_reserved(name)
-}
-
 // is_generic_name returns true if the current token is a generic name.
 fn (p Parser) is_generic_name() bool {
-	return p.tok.kind == .name && is_generic_name(p.tok.lit)
+	return p.tok.kind == .name && util.is_generic_type_name(p.tok.lit)
 }
 
 fn (mut p Parser) anon_fn() ast.AnonFn {

vlib/v/util/scanning.v

@@ -38,6 +38,12 @@ pub fn good_type_name(s string) bool {
 	return true
 }
 
+// is_generic_type_name returns true if the current token is a generic type name.
+[inline]
+pub fn is_generic_type_name(name string) bool {
+	return name.len == 1 && name.is_capital() && name != 'C'
+}
+
 pub fn cescaped_path(s string) string {
 	return s.replace('\\', '\\\\')
 }