cgen: fix tmp var redeclaration on const inited later (fix #24521) (fix #24517) (#24524)

vlib/v/gen/c/consts_and_globals.v

@@ -340,10 +340,15 @@ fn (mut g Gen) const_decl_init_later(mod string, name string, expr ast.Expr, typ
 		func := (expr_sym.info as ast.FnType).func
 		def = g.fn_var_signature(func.return_type, func.params.map(it.typ), cname)
 	}
+	init_str := init.str().trim_right('\n')
 	g.global_const_defs[util.no_dots(name)] = GlobalConstDef{
 		mod:       mod
 		def:       '${def}; // inited later'
-		init:      init.str().trim_right('\n')
+		init:      if init_str.count('\n') > 1 {
+			'{\n${init_str}\n}'
+		} else {
+			init_str
+		}
 		dep_names: g.table.dependent_names_in_expr(expr)
 	}
 	if g.is_autofree {

vlib/v/slow_tests/run_project_folders/issue_24521_constants_in_different_v_files/a.v

@@ -0,0 +1,12 @@
+module main
+
+import json
+
+pub struct JwtHeader {
+pub:
+	alg string
+	typ string
+	cty string
+}
+
+const f1 = json.encode(JwtHeader{ alg: '1', typ: '2', cty: '3' })

vlib/v/slow_tests/run_project_folders/issue_24521_constants_in_different_v_files/b.v

@@ -0,0 +1,5 @@
+module main
+
+import json
+
+const f2 = json.encode(JwtHeader{ alg: 'a', typ: 'b', cty: 'c' })

vlib/v/slow_tests/run_project_folders/issue_24521_constants_in_different_v_files/main.v

@@ -0,0 +1,7 @@
+module main
+
+fn main() {
+	println(f1)
+	println(f2)
+	println('OK')
+}