cgen: implement fixed array `.len` property (#6212)

vlib/v/ast/ast.v

@@ -106,7 +106,7 @@ pub:
 pub struct SelectorExpr {
 pub:
 	pos        token.Position
-	expr       Expr
+	expr       Expr // expr.field_name
 	field_name string
 pub mut:
 	expr_type  table.Type // type of `Foo` in `Foo.bar`

vlib/v/checker/checker.v

@@ -1470,7 +1470,7 @@ pub fn (mut c Checker) selector_expr(mut selector_expr ast.SelectorExpr) table.T
 	sym := c.table.get_type_symbol(c.unwrap_generic(typ))
 	field_name := selector_expr.field_name
 	// variadic
-	if typ.has_flag(.variadic) {
+	if typ.has_flag(.variadic) || sym.kind == .array_fixed {
 		if field_name == 'len' {
 			selector_expr.typ = table.int_type
 			return table.int_type

vlib/v/gen/cgen.v

@@ -2100,6 +2100,13 @@ fn (mut g Gen) expr(node ast.Expr) {
 			g.struct_init(node)
 		}
 		ast.SelectorExpr {
+			sym := g.table.get_type_symbol(node.expr_type)
+			if sym.kind == .array_fixed {
+				assert node.field_name == 'len'
+				info := sym.info as table.ArrayFixed
+				g.write('$info.size')
+				return
+			}
 			g.expr(node.expr)
 			if node.expr_type.is_ptr() {
 				g.write('->')

vlib/v/tests/fixed_array_test.v

@@ -11,7 +11,7 @@ fn test_fixed_array_can_be_assigned() {
 	v = [8]f64{}
 	assert v[1] == 0
 	// test slicing
-	for e in v[0..8] {
+	for e in v[0..v.len] {
 		assert e == 0
 	}
 	v = [8]f64{init: 3.0}
@@ -21,6 +21,7 @@ fn test_fixed_array_can_be_assigned() {
 fn test_fixed_array_can_be_used_in_declaration() {
 	x := 2.32
 	v := [1.0, x, 3.0,4.0,5.0,6.0,7.0,8.0]!!
+	assert v.len == 8
 	assert v[1] == x
 }
 
@@ -32,6 +33,7 @@ struct Context {
 
 fn test_fixed_array_can_be_assigned_to_a_struct_field() {
 	mut ctx := Context{}
+	assert ctx.vb.len == 8
 	x := 2.32
 	ctx.vb = [1.1, x, 3.3, 4.4, 5.0, 6.0, 7.0, 8.9]!!
 	assert ctx.vb[1] == x