{"record":{"id":"01aac45b72669666","repo":"go-delve/delve","slug":"evaluating-methods-not-supported-on-this-version-o","errorCode":null,"errorMessage":"evaluating methods not supported on this version of Go","messagePattern":"evaluating methods not supported on this version of Go","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"pkg/proc/eval.go","lineNumber":3214,"sourceCode":"\tv.Value = constant.MakeString(fn.Name)\n\tv.loaded = true\n\tv.Base = fn.Entry\n\treturn v, nil\n}\n\nfunc fakeArrayType(n uint64, fieldType godwarf.Type) godwarf.Type {\n\tstride := alignAddr(fieldType.Common().ByteSize, fieldType.Align())\n\treturn &godwarf.ArrayType{\n\t\tCommonType: godwarf.CommonType{\n\t\t\tReflectKind: reflect.Array,\n\t\t\tByteSize:    int64(n) * stride,\n\t\t\tName:        fmt.Sprintf(\"[%d]%s\", n, fieldType.String())},\n\t\tType:          fieldType,\n\t\tStrideBitSize: stride * 8,\n\t\tCount:         int64(n)}\n}\n\nvar errMethodEvalUnsupported = errors.New(\"evaluating methods not supported on this version of Go\")\n\nfunc (fn *Function) fakeType(bi *BinaryInfo, removeReceiver bool) (*godwarf.FuncType, error) {\n\tif producer := bi.Producer(); producer == \"\" || !goversion.ProducerAfterOrEqual(producer, 1, 10) {\n\t\t// versions of Go prior to 1.10 do not distinguish between parameters and\n\t\t// return values, therefore we can't use a subprogram DIE to derive a\n\t\t// function type.\n\t\treturn nil, errMethodEvalUnsupported\n\t}\n\t_, formalArgs, err := funcCallArgs(fn, bi, true)\n\tif err != nil {\n\t\treturn nil, err\n\t}\n\n\t// Only try and remove the receiver if it is actually being passed in as a formal argument.\n\t// In the case of:\n\t//\n\t// func (_ X) Method() { ... }\n\t//","sourceCodeStart":3196,"sourceCodeEnd":3232,"githubUrl":"https://github.com/go-delve/delve/blob/a23773e6c31361e43246bc43a424ee009679b174/pkg/proc/eval.go#L3196-L3232","documentation":"errMethodEvalUnsupported is returned when evaluating a method value/type requires synthesizing a function type from a subprogram DIE, which is only possible on Go 1.10+. Versions of Go prior to 1.10 do not distinguish parameters from return values in DWARF, so Delve cannot derive a method's fake type. The error surfaces through Function.fakeType in pkg/proc/eval.go.","triggerScenarios":"Debugging a binary produced by Go < 1.10 and evaluating an expression that requires a method's type (e.g. printing a method value or calling through an interface) which triggers fakeType with removeReceiver.","commonSituations":"Attaching Delve to a very old pre-built binary; CI environments with stale toolchains; legacy production binaries that were never rebuilt with a modern Go version.","solutions":["Rebuild the target binary with Go 1.10 or newer (ideally current Go)","If rebuilding is impossible, evaluate the method's underlying function value directly instead of the method expression","Upgrade Delve if needed to ensure it matches the target Go version"],"exampleFix":"// before: debug binary built with go1.9\ndlv> print x.MethodValue\n// after: rebuild\ngo build -gcflags=\"all=-N -l\" ./cmd/app\ndlv> print x.MethodValue","handlingStrategy":"validation","validationCode":"// check target's Go version before method evaluation\nproducer := bi.Producer() // must be >= go1.10 for method eval\n// CLI: dlv> version","typeGuard":null,"tryCatchPattern":"if err := eval(...); err != nil && strings.Contains(err.Error(), \"methods not supported\") {\n    // fall back to inspecting fields instead of methods\n}","preventionTips":["Build debug targets with a current Go toolchain","Avoid method-valued expressions when debugging legacy binaries","Check the producer version with 'version' before advanced expressions"],"tags":["go","eval","version-compat","methods"],"backgroundTag":"go-version-unsupported","analyzedSha":"a23773e6c31361e43246bc43a424ee009679b174","analyzedAt":"2026-08-31T15:12:45.221Z","schemaVersion":2},"datasetVersion":"2026-08-31T19:17:28.585Z"}