lint,decode,fuzz:: Fix nilerr warnings, one real one should be ignored for now

format/fuzz_test.go

@@ -82,7 +82,7 @@ func FuzzFormats(f *testing.F) {
 				return nil
 			}
 			if st, err := os.Stat(path); err != nil || st.IsDir() {
-				return nil
+				return err
 			}
 
 			b, readErr := ioutil.ReadFile(path)

pkg/interp/decode.go

@@ -258,6 +258,7 @@ func (i *Interp) _decode(c any, format string, opts decodeOpts) any {
 				if len(opts.Remain) > 0 {
 					if err := mapstruct.ToStruct(opts.Remain, &inArg); err != nil {
 						// TODO: currently ignores failed struct mappings
+						//nolint: nilerr
 						return f.DecodeInArg, nil
 					}
 				}