Terraform maps matching

maps.tf

locals {
    a = {
        "key1" = "valueX"
        "key2" = "valueY"
        "key3" = "valueZ"
    }

    b = {
        "key1" = "valueA"
        "key2" = "valueB"
        "key3" = "valueC"
    }

    c = merge([
        for ka,va in local.a : {
            for kb,vb in local.b: va => vb if ka == kb
        }
    ]...)
}

output "c" {
    value = local.c
}

The Terraform language has a general feature for turning lists/tuples into multiple arguments, by using the special symbol ... after the last argument expression