cgen: fix if expr with sumtype value of map (#16445)

vlib/v/gen/c/if.v

@@ -11,7 +11,10 @@ fn (mut g Gen) need_tmp_var_in_if(node ast.IfExpr) bool {
 			return true
 		}
 		for branch in node.branches {
-			if branch.cond is ast.IfGuardExpr || branch.stmts.len > 1 {
+			if branch.stmts.len > 1 {
+				return true
+			}
+			if g.need_tmp_var_in_expr(branch.cond) {
 				return true
 			}
 			if branch.stmts.len == 1 {
@@ -37,6 +40,17 @@ fn (mut g Gen) need_tmp_var_in_expr(expr ast.Expr) bool {
 				return true
 			}
 		}
+		ast.IfGuardExpr {
+			return true
+		}
+		ast.InfixExpr {
+			if g.need_tmp_var_in_expr(expr.left) {
+				return true
+			}
+			if g.need_tmp_var_in_expr(expr.right) {
+				return true
+			}
+		}
 		ast.MatchExpr {
 			return true
 		}

vlib/v/tests/if_expr_with_sumtype_map_test.v

@@ -0,0 +1,24 @@
+module main
+
+type ConfigValue = bool | int | string
+type ConfigMap = map[string]ConfigValue
+
+fn foo(conf ConfigMap) bool {
+	mut bar := false
+	// Check type
+	bar = if conf['baz'] or { false } is bool {
+		conf['baz'] or { false } as bool
+	} else {
+		false
+	} // Default value
+	return bar
+}
+
+fn test_if_expr_with_sumtype_map() {
+	conf := {
+		'baz': ConfigValue(123)
+	}
+	ret := foo(conf)
+	println(ret)
+	assert !ret
+}