Function handleErrorReturns

assertion/function/assertiontree/backprop_util.go:276–319

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: (1) if error return value = nil, create consumers for the non-error returns (2)

(rootNode *RootAssertionNode, retStmt *ast.ReturnStmt, results []ast.Expr, isNamedReturn bool)

//
// Note that `results` should be explicitly passed since `retStmt` of a named return will contain no results
func handleErrorReturns(rootNode *RootAssertionNode, retStmt *ast.ReturnStmt, results []ast.Expr, isNamedReturn bool) bool {
	if !typeshelper.FuncIsErrReturning(rootNode.FuncObj().Signature()) {
		return false
	}

	errRetIndex := len(results) - 1
	errRetExpr := results[errRetIndex]     // n-th expression
	nonErrRetExpr := results[:errRetIndex] // n-1 expressions

	// default tracking to support potential "always safe" cases
	createReturnConsumersForAlwaysSafe(rootNode, nonErrRetExpr, retStmt, isNamedReturn)

	// check if the error return is at all guarding any nilable returns, such as pointers, maps, and slices
	if isErrorReturnNil(rootNode, errRetExpr) {
		// if error is the only return expression in the statement, then create a consumer for it, else create consumers for the non-error return expressions
		if len(nonErrRetExpr) == 0 {
			createConsumerForErrorReturn(rootNode, errRetExpr, errRetIndex, retStmt, isNamedReturn)
		} else {
			// create general return consume triggers for all n-1 (non-error) return expressions
			createGeneralReturnConsumers(rootNode, nonErrRetExpr, retStmt, isNamedReturn)
		}

		// TODO: handle struct init in the context of error return in a better way in a follow up diff
		if rootNode.functionContext.functionConfig.EnableStructInitCheck {
			for i := range results {
				rootNode.addConsumptionsForFieldsOfReturns(results[i], i)
			}
		}
	} else if isErrorReturnNonnil(rootNode, errRetExpr) {
		// create consume trigger for only the error return
		createConsumerForErrorReturn(rootNode, errRetExpr, errRetIndex, retStmt, isNamedReturn)
	} else {
		// the nilability of error return is unknown, hence create special consume triggers for all returns
		createSpecialConsumersForAllReturns(rootNode, nonErrRetExpr, errRetExpr, errRetIndex, retStmt, isNamedReturn)

		// TODO: handle struct init in the context of error return in a better way in a follow up diff
		if rootNode.functionContext.functionConfig.EnableStructInitCheck {
			for i := range results {
				rootNode.addConsumptionsForFieldsOfReturns(results[i], i)
			}
		}
	}
	return true
}

// handleBooleanReturns handles the special case for boolean (`ok`) returning functions (n-th result of type `bool`
// which guards at least one of the first n-1 non-bool results). Similar to the handling of error returning functions,