diff --git a/vlib/v/checker/str.v b/vlib/v/checker/str.v
index b6b82b7985ffc9..f5680eabe5d0d3 100644
--- a/vlib/v/checker/str.v
+++ b/vlib/v/checker/str.v
@@ -85,7 +85,8 @@ fn (mut c Checker) string_inter_lit(mut node ast.StringInterLiteral) ast.Type {
 					c.error('no known default format for type `${c.table.get_type_name(ftyp)}`',
 						node.fmt_poss[i])
 				}
-			} else if c.comptime.is_comptime(expr) && c.comptime.get_type(expr) != ast.void_type {
+			} else if c.comptime.is_comptime(expr)
+				&& c.comptime.get_type_or_default(expr, ast.void_type) != ast.void_type {
 				// still `_` placeholder for comptime variable without specifier
 				node.need_fmts[i] = false
 			} else {
diff --git a/vlib/v/comptime/comptimeinfo.v b/vlib/v/comptime/comptimeinfo.v
index 2de799a049c2b1..156ab624c3ef47 100644
--- a/vlib/v/comptime/comptimeinfo.v
+++ b/vlib/v/comptime/comptimeinfo.v
@@ -61,6 +61,15 @@ pub fn (mut ct ComptimeInfo) is_comptime(node ast.Expr) bool {
 				false
 			}
 		}
+		ast.SelectorExpr {
+			return node.expr is ast.Ident && node.expr.ct_expr
+		}
+		ast.InfixExpr {
+			return ct.is_comptime(node.left) || ct.is_comptime(node.right)
+		}
+		ast.ParExpr {
+			return ct.is_comptime(node.expr)
+		}
 		else {
 			false
 		}
@@ -120,6 +129,26 @@ pub fn (mut ct ComptimeInfo) get_type_or_default(node ast.Expr, default_typ ast.
 				return if ctyp != ast.void_type { ctyp } else { default_typ }
 			}
 		}
+		ast.SelectorExpr {
+			if node.expr is ast.Ident && node.expr.ct_expr {
+				struct_typ := ct.resolver.unwrap_generic(ct.get_type(node.expr))
+				struct_sym := ct.table.final_sym(struct_typ)
+				// Struct[T] can have field with generic type
+				if struct_sym.info is ast.Struct && struct_sym.info.generic_types.len > 0 {
+					if field := ct.table.find_field(struct_sym, node.field_name) {
+						return field.typ
+					}
+				}
+			}
+		}
+		ast.ParExpr {
+			return ct.get_type_or_default(node.expr, default_typ)
+		}
+		ast.InfixExpr {
+			if node.op in [.plus, .minus, .mul, .div, .mod] {
+				return ct.get_type_or_default(node.left, default_typ)
+			}
+		}
 		else {
 			return default_typ
 		}
diff --git a/vlib/v/gen/c/infix.v b/vlib/v/gen/c/infix.v
index c33b40a131d79b..9f1888f1e54fda 100644
--- a/vlib/v/gen/c/infix.v
+++ b/vlib/v/gen/c/infix.v
@@ -925,8 +925,8 @@ fn (mut g Gen) gen_interface_is_op(node ast.InfixExpr) {
 // infix_expr_arithmetic_op generates code for `+`, `-`, `*`, `/`, and `%`
 // It handles operator overloading when necessary
 fn (mut g Gen) infix_expr_arithmetic_op(node ast.InfixExpr) {
-	left := g.unwrap(node.left_type)
-	right := g.unwrap(node.right_type)
+	left := g.unwrap(g.comptime.get_type_or_default(node.left, node.left_type))
+	right := g.unwrap(g.comptime.get_type_or_default(node.right, node.right_type))
 	if left.sym.info is ast.Struct && left.sym.info.generic_types.len > 0 {
 		mut method_name := left.sym.cname + '_' + util.replace_op(node.op.str())
 		method_name = g.generic_fn_name(left.sym.info.concrete_types, method_name)
@@ -1188,7 +1188,11 @@ fn (mut g Gen) gen_plain_infix_expr(node ast.InfixExpr) {
 		&& node.op in [.plus, .minus, .mul, .div, .mod] && !(g.pref.translated
 		|| g.file.is_translated)
 	if needs_cast {
-		typ_str := g.styp(node.promoted_type)
+		typ_str := if g.comptime.is_comptime(node.left) {
+			g.styp(g.comptime.get_type_or_default(node.left, node.promoted_type))
+		} else {
+			g.styp(node.promoted_type)
+		}
 		g.write('(${typ_str})(')
 	}
 	if node.left_type.is_ptr() && node.left.is_auto_deref_var() && !node.right_type.is_pointer() {
diff --git a/vlib/v/gen/c/str_intp.v b/vlib/v/gen/c/str_intp.v
index 219b1f6e8a1b88..52d9149ac493cd 100644
--- a/vlib/v/gen/c/str_intp.v
+++ b/vlib/v/gen/c/str_intp.v
@@ -241,7 +241,7 @@ fn (mut g Gen) string_inter_literal(node ast.StringInterLiteral) {
 	mut fmts := node_.fmts.clone()
 	for i, mut expr in node_.exprs {
 		if g.comptime.is_comptime(expr) {
-			ctyp := g.comptime.get_type(expr)
+			ctyp := g.comptime.get_type_or_default(expr, node_.expr_types[i])
 			if ctyp != ast.void_type {
 				node_.expr_types[i] = ctyp
 				if node_.fmts[i] == `_` {
diff --git a/vlib/v/parser/fn.v b/vlib/v/parser/fn.v
index f265820c7347f3..7df0d5372c77b0 100644
--- a/vlib/v/parser/fn.v
+++ b/vlib/v/parser/fn.v
@@ -512,7 +512,7 @@ run them via `v file.v` instead',
 				pos:           param.pos
 				is_used:       is_pub || no_body || (is_method && k == 0) || p.builtin_mod
 				is_arg:        true
-				ct_type_var:   if (!is_method || k > 0) && param.typ.has_flag(.generic)
+				ct_type_var:   if (!is_method || k >= 0) && param.typ.has_flag(.generic)
 					&& !param.typ.has_flag(.variadic) {
 					.generic_param
 				} else {
diff --git a/vlib/v/tests/generics/generic_selector_type_test.v b/vlib/v/tests/generics/generic_selector_type_test.v
new file mode 100644
index 00000000000000..6643b4cef0e3e7
--- /dev/null
+++ b/vlib/v/tests/generics/generic_selector_type_test.v
@@ -0,0 +1,12 @@
+import math.vec
+
+type UnusedType = vec.Vec3[f32]
+
+fn (n UnusedType) unused_function() f32 {
+	return n.mul_scalar(2).magnitude()
+}
+
+fn test_main() {
+	assert vec.Vec3[f32]{0.5, 0.5, 0.5}.magnitude() == f32(0.8660254)
+	assert vec.Vec3[f32]{1.5, 1.5, 1.5}.magnitude() == f32(2.598076)
+}