v: add a $Option comp-time type, to enable: $for f in Test.fields { $if f.typ is $Option { } } (#17546)

vlib/v/ast/ast.v

@@ -128,6 +128,7 @@ pub enum ComptimeTypeKind {
 	enum_
 	alias
 	function
+	option
 }
 
 pub struct ComptimeType {
@@ -148,6 +149,7 @@ pub fn (cty ComptimeType) str() string {
 		.enum_ { '\$Enum' }
 		.alias { '\$Alias' }
 		.function { '\$Function' }
+		.option { '\$Option' }
 	}
 }
 

vlib/v/ast/table.v

@@ -2279,6 +2279,9 @@ pub fn (t &Table) is_comptime_type(x Type, y ComptimeType) bool {
 		.function {
 			return x_kind == .function
 		}
+		.option {
+			return x.has_flag(.option)
+		}
 	}
 }
 

vlib/v/fmt/fmt.v

@@ -741,6 +741,7 @@ pub fn (mut f Fmt) expr(node_ ast.Expr) {
 				.enum_ { f.write('\$Enum') }
 				.alias { f.write('\$Alias') }
 				.function { f.write('\$Function') }
+				.option { f.write('\$Option') }
 			}
 		}
 	}

vlib/v/gen/golang/golang.v

@@ -661,6 +661,7 @@ pub fn (mut f Gen) expr(node_ ast.Expr) {
 				.enum_ { f.write('\$Enum') }
 				.alias { f.write('\$Alias') }
 				.function { f.write('\$Function') }
+				.option { f.write('\$Option') }
 			}
 		}
 	}

vlib/v/parser/comptime.v

@@ -12,7 +12,7 @@ const (
 	supported_comptime_calls = ['html', 'tmpl', 'env', 'embed_file', 'pkgconfig', 'compile_error',
 		'compile_warn']
 	comptime_types           = ['Map', 'Array', 'Int', 'Float', 'Struct', 'Interface', 'Enum',
-		'Sumtype', 'Alias', 'Function']
+		'Sumtype', 'Alias', 'Function', 'Option']
 )
 
 pub fn (mut p Parser) parse_comptime_type() ast.ComptimeType {
@@ -55,6 +55,9 @@ pub fn (mut p Parser) parse_comptime_type() ast.ComptimeType {
 		'Sumtype' {
 			cty = .sum_type
 		}
+		'Option' {
+			cty = .option
+		}
 		else {}
 	}
 	node = ast.ComptimeType{cty, node.pos}

vlib/v/tests/comptime_option_field_test.v

@@ -0,0 +1,18 @@
+struct Test {
+	a ?int
+	b ?f64
+	c ?string
+	d int
+	e f64
+	f string
+}
+
+fn test_option_comptime() {
+	mut opts := []string{}
+	$for f in Test.fields {
+		$if f.typ is $Option {
+			opts << f.name
+		}
+	}
+	assert opts == ['a', 'b', 'c']
+}