Function isErrorReturnNonnil

assertion/function/assertiontree/backprop_util.go:247–267

isErrorReturnNonnil returns true if the error return is guaranteed to be nonnil, false otherwise

(rootNode *RootAssertionNode, errRet ast.Expr)

// isErrorReturnNonnil returns true if the error return is guaranteed to be nonnil, false otherwise
func isErrorReturnNonnil(rootNode *RootAssertionNode, errRet ast.Expr) bool {
	// The error value's type is not inhabited by nil (e.g., a named basic type such as
	// `type Error string`), so it can never be nil.
	if rootNode.Pass().ExprBarsNilness(errRet) {
		return true
	}
	// The error value is a custom error type (struct or pointer-to-struct), e.g. a returned
	// `&MyErr{}` or `MyErr{}`. Such values are assumed non-nil: a concrete value boxed into the
	// error interface yields a non-nil interface.
	if t := rootNode.Pass().TypesInfo.TypeOf(errRet); typeshelper.AsDeeplyStruct(t) != nil {
		return true
	}
	// The error value is the return of a hook-modeled function known to produce a non-nil error.
	if callExpr, ok := errRet.(*ast.CallExpr); ok {
		if hook.AssumeReturn(rootNode.Pass(), callExpr) != nil {
			return true
		}
	}

	return false
}

// handleErrorReturns handles the special case for error returning functions (n-th result of type `error` which guards at least one of the first n-1 non-error results).
// It generates consumers by applying the error contract: