feat: Stop linting arguments that are .Error() expressions

This pattern is distinct enough to not warant extra caution. It can now
be used as an opt-out pattern to explicityly not wrap an error.

Author: polyfloyd

errorlint/lint.go

@@ -47,7 +47,7 @@ func LintFmtErrorfCalls(fset *token.FileSet, info types.Info, multipleWraps bool
 		args := call.Args[1:]
 		wrapCount := 0
 		for i := 0; i < len(args) && i < len(formatVerbs); i++ {
-			if !implementsError(info.Types[args[i]].Type) && !isErrorStringCall(info, args[i]) {
+			if !implementsError(info.Types[args[i]].Type) {
 				continue
 			}
 			verb := formatVerbs[i]
@@ -78,20 +78,6 @@ func LintFmtErrorfCalls(fset *token.FileSet, info types.Info, multipleWraps bool
 	return lints
 }
 
-// isErrorStringCall tests whether the expression is a string expression that
-// is the result of an `(error).Error()` method call.
-func isErrorStringCall(info types.Info, expr ast.Expr) bool {
-	if info.Types[expr].Type.String() == "string" {
-		if call, ok := expr.(*ast.CallExpr); ok {
-			if callSel, ok := call.Fun.(*ast.SelectorExpr); ok {
-				fun := info.Uses[callSel.Sel].(*types.Func)
-				return fun.Type().String() == "func() string" && fun.Name() == "Error"
-			}
-		}
-	}
-	return false
-}
-
 // printfFormatStringVerbs returns a normalized list of all the verbs that are used per argument to
 // the printf function. The index of each returned element corresponds to the index of the
 // respective argument.

errorlint/testdata/src/fmterrorf/fmterrorf.go

@@ -43,12 +43,12 @@ func ErrorMultipleWrapsWithCustomError() error {
 
 func ErrorStringFormat() error {
 	err := errors.New("oops")
-	return fmt.Errorf("error: %s", err.Error()) // want "non-wrapping format verb for fmt.Errorf. Use `%w` to format errors"
+	return fmt.Errorf("error: %s", err.Error())
 }
 
 func ErrorStringFormatCustomError() error {
 	err := MyError{}
-	return fmt.Errorf("error: %s", err.Error()) // want "non-wrapping format verb for fmt.Errorf. Use `%w` to format errors"
+	return fmt.Errorf("error: %s", err.Error())
 }
 
 func NotAnError() error {