Method TypeCheck

postgres/parser/sem/tree/type_check.go:266–324

TypeCheck implements the Expr interface.

(
	ctx context.Context, semaCtx *SemaContext, desired *types.T,
)

// TypeCheck implements the Expr interface.
func (expr *BinaryExpr) TypeCheck(
	ctx context.Context, semaCtx *SemaContext, desired *types.T,
) (TypedExpr, error) {
	ops := BinOps[expr.Operator]

	typedSubExprs, fns, err := typeCheckOverloadedExprs(ctx, semaCtx, desired, ops, true, expr.Left, expr.Right)
	if err != nil {
		return nil, err
	}

	leftTyped, rightTyped := typedSubExprs[0], typedSubExprs[1]
	leftReturn := leftTyped.ResolvedType()
	rightReturn := rightTyped.ResolvedType()

	// Return NULL if at least one overload is possible, NULL is an argument,
	// and none of the overloads accept NULL.
	if leftReturn.Family() == types.UnknownFamily || rightReturn.Family() == types.UnknownFamily {
		if len(fns) > 0 {
			noneAcceptNull := true
			for _, e := range fns {
				if e.(*BinOp).NullableArgs {
					noneAcceptNull = false
					break
				}
			}
			if noneAcceptNull {
				return DNull, nil
			}
		}
	}

	// Throw a typing error if overload resolution found either no compatible candidates
	// or if it found an ambiguity.
	if len(fns) != 1 {
		var desStr string
		if desired.Family() != types.AnyFamily {
			desStr = fmt.Sprintf(" (desired <%s>)", desired)
		}
		sig := fmt.Sprintf("<%s> %s <%s>%s", leftReturn, expr.Operator, rightReturn, desStr)
		if len(fns) == 0 {
			return nil,
				pgerror.Newf(pgcode.InvalidParameterValue, unsupportedBinaryOpErrFmt, sig)
		}
		fnsStr := formatCandidates(expr.Operator.String(), fns)
		err = pgerror.Newf(pgcode.AmbiguousFunction, ambiguousBinaryOpErrFmt, sig)
		err = errors.WithHintf(err, candidatesHintFmt, fnsStr)
		return nil, err
	}

	binOp := fns[0].(*BinOp)
	if err := semaCtx.checkVolatility(binOp.Volatility); err != nil {
		return nil, pgerror.Wrapf(err, pgcode.InvalidParameterValue, "%s", expr.Operator)
	}

	expr.Left, expr.Right = leftTyped, rightTyped
	expr.Fn = binOp
	expr.typ = binOp.returnType()(typedSubExprs)
	return expr, nil