Kotlin client warnings

[wing328]

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Description

When running gradle test with the Kotline petstore client, I got the following warning:

> Task :compileKotlin
w: /Users/williamcheng/Code/openapi-generator/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/apis/PetApi.kt: (48, 13): 'when' is exhaustive so 'else' is redundant here
w: /Users/williamcheng/Code/openapi-generator/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/apis/PetApi.kt: (80, 13): 'when' is exhaustive so 'else' is redundant here
w: /Users/williamcheng/Code/openapi-generator/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/apis/PetApi.kt: (112, 13): 'when' is exhaustive so 'else' is redundant here
w: /Users/williamcheng/Code/openapi-generator/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/apis/PetApi.kt: (144, 13): 'when' is exhaustive so 'else' is redundant here
w: /Users/williamcheng/Code/openapi-generator/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/apis/PetApi.kt: (176, 13): 'when' is exhaustive so 'else' is redundant here
w: /Users/williamcheng/Code/openapi-generator/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/apis/PetApi.kt: (207, 13): 'when' is exhaustive so 'else' is redundant here
w: /Users/williamcheng/Code/openapi-generator/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/apis/PetApi.kt: (240, 13): 'when' is exhaustive so 'else' is redundant here
w: /Users/williamcheng/Code/openapi-generator/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/apis/PetApi.kt: (274, 13): 'when' is exhaustive so 'else' is redundant here
w: /Users/williamcheng/Code/openapi-generator/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/apis/StoreApi.kt: (47, 13): 'when' is exhaustive so 'else' is redundant here
w: /Users/williamcheng/Code/openapi-generator/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/apis/StoreApi.kt: (78, 13): 'when' is exhaustive so 'else' is redundant here
w: /Users/williamcheng/Code/openapi-generator/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/apis/StoreApi.kt: (110, 13): 'when' is exhaustive so 'else' is redundant here
w: /Users/williamcheng/Code/openapi-generator/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/apis/StoreApi.kt: (142, 13): 'when' is exhaustive so 'else' is redundant here
w: /Users/williamcheng/Code/openapi-generator/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/apis/UserApi.kt: (47, 13): 'when' is exhaustive so 'else' is redundant here
w: /Users/williamcheng/Code/openapi-generator/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/apis/UserApi.kt: (78, 13): 'when' is exhaustive so 'else' is redundant here
w: /Users/williamcheng/Code/openapi-generator/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/apis/UserApi.kt: (109, 13): 'when' is exhaustive so 'else' is redundant here
w: /Users/williamcheng/Code/openapi-generator/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/apis/UserApi.kt: (140, 13): 'when' is exhaustive so 'else' is redundant here
w: /Users/williamcheng/Code/openapi-generator/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/apis/UserApi.kt: (172, 13): 'when' is exhaustive so 'else' is redundant here
w: /Users/williamcheng/Code/openapi-generator/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/apis/UserApi.kt: (205, 13): 'when' is exhaustive so 'else' is redundant here
w: /Users/williamcheng/Code/openapi-generator/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/apis/UserApi.kt: (235, 13): 'when' is exhaustive so 'else' is redundant here
w: /Users/williamcheng/Code/openapi-generator/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/apis/UserApi.kt: (267, 13): 'when' is exhaustive so 'else' is redundant here

openapi-generator version

Latest master

Command line used for generation

cd samples/client/petstore/kotlin && gradle test

Steps to reproduce

Related issues/PRs

Suggest a fix

If anyone has time to contribute a PR to address these warnings, please let us know.

Kotlin client mustache templates: https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/main/resources/kotlin-client/api.mustache