go compile_error ai_generated true

too many return values have (T, error) want (T)

ID: go/too-many-return-values

Also available as: JSON · Markdown · 中文
90%Fix Rate
88%Confidence
1Evidence
2023-06-20First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
go1.20 active — — —
go1.21 active — — —
go1.22 active — — —

Root Cause

A function expecting a single return value is being assigned or used where a multi-return function is called, often due to mismatched function signatures or missing error handling.

generic

中文

期望单个返回值的函数被赋值或用于调用多返回值函数的位置，通常是由于函数签名不匹配或缺少错误处理。

Official Documentation

https://go.dev/ref/spec#Function_types

Workarounds

  1. 95% success Assign both return values to variables and handle the error: val, err := someFunc(); if err != nil { ... } 
    Assign both return values to variables and handle the error: val, err := someFunc(); if err != nil { ... }
  2. 85% success If the function should return only one value, wrap it in a helper: func wrapper() T { val, _ := someFunc(); return val } 
    If the function should return only one value, wrap it in a helper: func wrapper() T { val, _ := someFunc(); return val }

中文步骤

  1. Assign both return values to variables and handle the error: val, err := someFunc(); if err != nil { ... }
  2. If the function should return only one value, wrap it in a helper: func wrapper() T { val, _ := someFunc(); return val }

Dead Ends

Common approaches that don't work:

  1. Adding an underscore to ignore the error: val, _ := someFunc() 90% fail

    This only works if the caller expects two values; if the caller expects one, the compile error persists.

  2. Changing the function signature to remove the error return 95% fail

    Modifying the library function breaks its contract and may cause other compilation errors.

  3. Using a type assertion on the result 98% fail

    Type assertion cannot reduce the number of return values; it only works on interfaces.