Merge pull request #332750 from K900/better-env-errors

          then attrs.name + hostSuffix

          else

            # we cannot coerce null to a string below

            assert assertMsg (attrs ? version && attrs.version != null) "The ‘version’ attribute cannot be null.";

            assert assertMsg (attrs ? version && attrs.version != null) "The `version` attribute cannot be null.";

            "${attrs.pname}${staticMarker}${hostSuffix}-${attrs.version}"

        );

    }) // {

  checkedEnv =

    let

      overlappingNames = attrNames (builtins.intersectAttrs env derivationArg);

      prettyPrint = lib.generators.toPretty {};

      makeError = name: "  - ${name}: in `env`: ${prettyPrint env.${name}}; in derivation arguments: ${prettyPrint derivationArg.${name}}";

      errors = lib.concatMapStringsSep "\n" makeError overlappingNames;

    in

    assert assertMsg envIsExportable

      "When using structured attributes, `env` must be an attribute set of environment variables.";

    assert assertMsg (overlappingNames == [ ])

      "The ‘env’ attribute set cannot contain any attributes passed to derivation. The following attributes are overlapping: ${concatStringsSep ", " overlappingNames}";

      "The `env` attribute set cannot contain any attributes passed to derivation. The following attributes are overlapping:\n${errors}";

    mapAttrs

      (n: v: assert assertMsg (isString v || isBool v || isInt v || isDerivation v)

        "The ‘env’ attribute set can only contain derivation, string, boolean or integer attributes. The ‘${n}’ attribute is of type ${builtins.typeOf v}."; v)

        "The `env` attribute set can only contain derivation, string, boolean or integer attributes. The `${n}` attribute is of type ${builtins.typeOf v}."; v)

      env;

  # Fixed-output derivations may not reference other paths, which means that