fix: Allow type assertions of non-error types (fixes #61)

errorlint/lint.go

@@ -307,6 +307,11 @@ func LintErrorTypeAssertions(fset *token.FileSet, info *TypesInfoExt) []analysis
 			continue
 		}
 
+		// If the asserted type is not an error, allow the expression.
+		if !implementsError(info.TypesInfo.Types[typeAssert.Type].Type) {
+			continue
+		}
+
 		lints = append(lints, analysis.Diagnostic{
 			Message: "type assertion on error will fail on wrapped errors. Use errors.As to check for specific errors",
 			Pos:     typeAssert.Pos(),

errorlint/testdata/src/issues/github-61.go

@@ -0,0 +1,12 @@
+package issues
+
+import (
+	"errors"
+)
+
+func Issue61() {
+	err := errors.Join(errors.New("err1"), errors.New("err2"))
+	errs, ok := err.(interface{ Unwrap() []error })
+	_ = errs
+	_ = ok
+}