errcheck doesn't detect all unchecked type assertion

[pierrre]

Thank you for creating the issue!

• Yes, I'm using a binary release within 2 latest major releases. Only such installations are supported.
• Yes, I've searched similar issues on GitHub and didn't find any.
• Yes, I've included all information below (version, config, etc).

Please include the following information:

Version of golangci-lint

$ golangci-lint --version
golangci-lint has version 1.21.0 built from 645e794 on 2019-10-15T18:16:56Z

Config file

$ cat .golangci.yml
run:
  timeout: "10m"
linters:
  disable-all: true
  enable:
    - "bodyclose"
    - "deadcode"
    - "depguard"
    - "errcheck"
    - "gocritic"
    - "gocyclo"
    - "gofmt"
    - "goimports"
    - "golint"
    - "govet"
    - "ineffassign"
    - "megacheck"
    - "misspell"
    - "nakedret"
    - "structcheck"
    - "unconvert"
    - "unparam"
    - "varcheck"
linters-settings:
  depguard:
    list-type: blacklist
    include-go-root: true
    packages:
      - errors
      - reflect
      - unsafe
      - github.com/pkg/errors
  errcheck:
    check-type-assertions: true
  gocyclo:
    min-complexity: 10
  govet:
    enable-all: true
issues:
  exclude-use-default: false
  max-issues-per-linter: 0
  max-same-issues: 0

Go environment

$ go version && go env
go version go1.13.5 linux/amd64
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/pierre/.cache/go-build"
GOENV="/home/pierre/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/pierre/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/home/pierre/.gimme/versions/go1.13.5.src"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/home/pierre/.gimme/versions/go1.13.5.src/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/pierre/gosrc/github.com/xxx/yyy/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build810139123=/tmp/go-build -gno-record-gcc-switches"

Verbose output of running

$ golangci-lint run -v
INFO [config_reader] Config search paths: [./ /home/pierre/gosrc/github.com/xxx/yyy /home/pierre/gosrc/github.com/xxx /home/pierre/gosrc/github.com /home/pierre/gosrc /home/pierre /home /] 
INFO [config_reader] Used config file .golangci.yml 
INFO [lintersdb] Active 20 linters: [bodyclose deadcode depguard errcheck gocritic gocyclo gofmt goimports golint gosimple govet ineffassign misspell nakedret staticcheck structcheck unconvert unparam unused varcheck] 
INFO [loader] Go packages loading at mode 575 (exports_file|imports|compiled_files|deps|files|name|types_sizes) took 235.781777ms 
INFO [runner/filename_unadjuster] Pre-built 0 adjustments in 24.339956ms 
INFO [runner/goanalysis_metalinter/goanalysis] analyzers took 25.433211455s with top 10 stages: buildssa: 9.13999065s, goimports: 1.69246075s, gofmt: 1.231308728s, unparam: 922.471835ms, golint: 834.866973ms, ineffassign: 768.164647ms, misspell: 738.716443ms, gocritic: 684.814951ms, SA4014: 671.62614ms, deadcode: 632.376094ms 
INFO [runner/unused/goanalysis] analyzers took 1.973672294s with top 10 stages: buildssa: 1.441568036s, U1000: 532.104258ms 
INFO [runner] Issues before processing: 18, after processing: 0 
INFO [runner] Processors filtering stat (out/in): filename_unadjuster: 18/18, identifier_marker: 18/18, exclude: 18/18, path_prettifier: 18/18, skip_files: 18/18, autogenerated_exclude: 18/18, nolint: 0/18, cgo: 18/18, skip_dirs: 18/18, exclude-rules: 18/18 
INFO [runner] processing took 5.717866ms with stages: nolint: 5.046802ms, path_prettifier: 242.312µs, identifier_marker: 211.745µs, autogenerated_exclude: 109.443µs, skip_dirs: 98.829µs, cgo: 4.679µs, filename_unadjuster: 1.501µs, max_same_issues: 683ns, skip_files: 281ns, diff: 255ns, max_from_linter: 241ns, uniq_by_line: 187ns, exclude-rules: 187ns, path_shortener: 185ns, max_per_file_from_linter: 182ns, source_code: 182ns, exclude: 172ns 
INFO [runner] linters took 3.431985751s with stages: goanalysis_metalinter: 2.888784135s, unused: 537.425552ms 
INFO File cache stats: 382 entries of total size 1.2MiB 
INFO Memory: 38 samples, avg is 368.0MB, max is 610.1MB 
INFO Execution took 3.696656595s

I've configured errcheck to report unchecked type assertion.
However, in this code:

if filter["messages_sent.messageid"].(map[string]interface{})["$ne"] != nil {

the type assertion is not checked, but it's not reported.
filter is a bson.M from github.com/globalsign/mgo/bson.

[pierrre]

thank you ! 👍