type_resolver: fix generic selector field type resolving (continuation of #23456) (#23473)

vlib/math/stats/stats.v

@@ -67,14 +67,14 @@ pub fn harmonic_mean[T](data []T) T {
 		for v in data {
 			sum += f64(1.0) / v
 		}
-		return f64(data.len / sum)
+		return f64(f64(data.len) / sum)
 	} $else {
 		// use f32 for f32/int/...
 		mut sum := f32(0)
 		for v in data {
 			sum += f32(1.0) / f32(v)
 		}
-		return T(data.len / sum)
+		return T(f32(data.len) / sum)
 	}
 }
 

vlib/v/gen/c/infix.v

@@ -1189,8 +1189,8 @@ fn (mut g Gen) gen_plain_infix_expr(node ast.InfixExpr) {
 		|| g.file.is_translated)
 	if needs_cast {
 		typ_str := if node.left_ct_expr {
-			g.styp(g.type_resolver.get_type_or_default(node.left, node.promoted_type))
+			g.styp(g.type_resolver.get_type_or_default(node.left, node.left_type))
-		} else if node.right_ct_expr {
+		} else if node.left !in [ast.Ident, ast.CastExpr] && node.right_ct_expr {
 			g.styp(g.type_resolver.get_type_or_default(node.right, node.promoted_type))
 		} else {
 			g.styp(node.promoted_type)

vlib/v/tests/generics/generic_selector_len_test.v

@@ -0,0 +1,17 @@
+struct Foo[T] {
+	len T
+}
+
+fn t[T](val T) string {
+	a := val.len + val.len
+	println(a)
+	return a.str()
+}
+
+fn test_main() {
+	assert t(Foo[string]{ len: 'hello' }) == 'hellohello'
+	assert t(Foo[int]{ len: 123 }) == '246'
+	assert t([1, 2, 3]) == '6'
+	assert t([1.2, 2.2, 3.3]) == '6'
+	assert t(['', '', '']) == '6'
+}

vlib/v/type_resolver/comptime_resolver.v

@@ -47,7 +47,7 @@ pub fn (t &ResolverInfo) is_comptime(node ast.Expr) bool {
 			}
 		}
 		ast.SelectorExpr {
-			return node.expr is ast.Ident && node.expr.ct_expr && node.field_name != 'len'
+			return node.expr is ast.Ident && node.expr.ct_expr
 		}
 		ast.InfixExpr {
 			return node.left_ct_expr || node.right_ct_expr
@@ -83,6 +83,8 @@ pub fn (t &ResolverInfo) get_ct_type_var(node ast.Expr) ast.ComptimeVarKind {
 		return t.get_ct_type_var(node.left)
 	} else if node is ast.ParExpr {
 		return t.get_ct_type_var(node.expr)
+	} else if node is ast.SelectorExpr {
+		return t.get_ct_type_var(node.expr)
 	}
 	return .no_comptime
 }