ast, cgen: fix as cast with call expr (fix #19453)

cmd/tools/vtest-self.v

@@ -255,7 +255,8 @@ const (
 		'do_not_remove',
 		'vlib/v/tests/const_fixed_array_containing_references_to_itself_test.v', // error C2099: initializer is not a constant
 		'vlib/v/tests/const_and_global_with_same_name_test.v', // error C2099: initializer is not a constant
-		'vlib/v/tests/sumtype_as_cast_test.v', // error: cannot support compound statement expression ({expr; expr; expr;})
+		'vlib/v/tests/sumtype_as_cast_1_test.v', // error: cannot support compound statement expression ({expr; expr; expr;})
+		'vlib/v/tests/sumtype_as_cast_2_test.v', // error: cannot support compound statement expression ({expr; expr; expr;})
 		'vlib/v/tests/project_with_cpp_code/compiling_cpp_files_with_a_cplusplus_compiler_test.v', // TODO
 	]
 	skip_on_windows               = [

vlib/v/ast/ast.v

@@ -2079,6 +2079,15 @@ pub fn (e &Expr) is_lockable() bool {
 	}
 }
 
+// returns if an expression has call expr`
+pub fn (e &Expr) has_fn_call() bool {
+	return match e {
+		CallExpr { true }
+		SelectorExpr { e.expr.has_fn_call() }
+		else { false }
+	}
+}
+
 // CTempVar is used in cgen only, to hold nodes for temporary variables
 pub struct CTempVar {
 pub:

vlib/v/gen/c/cgen.v

@@ -6564,7 +6564,7 @@ fn (mut g Gen) as_cast(node ast.AsCast) {
 	mut expr_type_sym := g.table.sym(g.unwrap_generic(node.expr_type))
 	if mut expr_type_sym.info is ast.SumType {
 		dot := if node.expr_type.is_ptr() { '->' } else { '.' }
-		if node.expr is ast.CallExpr && !g.is_cc_msvc {
+		if node.expr.has_fn_call() && !g.is_cc_msvc {
 			tmp_var := g.new_tmp_var()
 			expr_styp := g.typ(node.expr_type)
 			g.write('({ ${expr_styp} ${tmp_var} = ')

vlib/v/tests/sumtype_as_cast_2_test.v

@@ -0,0 +1,31 @@
+type Numbers = int | string
+
+struct Values {
+	value Numbers
+}
+
+struct Wrapper {
+	element []Values
+mut:
+	index int
+}
+
+fn (mut instance Wrapper) get() Values {
+	instance.index++
+	return instance.element[0]
+}
+
+fn test_sumtype_as_cast() {
+	mut wrapper := Wrapper{
+		element: [
+			Values{
+				value: 1
+			},
+			Values{
+				value: '2'
+			},
+		]
+	}
+	println(wrapper.get().value as int)
+	assert wrapper.index == 1
+}