Function checkReturn

pkg/sql/sem/tree/overload.go:808–860

checkReturn checks the number of remaining overloaded function implementations. Returns ok=true if we should stop overload resolution, and returning either 1. the chosen overload in a slice, or 2. nil, along with the typed arguments. This modifies values within s as scratch slices, but only in the c

(
	ctx *SemaContext, s *typeCheckOverloadState,
)

// it returns true, which signals to the calling function that it should
// immediately return, so any mutations to s are irrelevant.
func checkReturn(
	ctx *SemaContext, s *typeCheckOverloadState,
) (ok bool, _ []TypedExpr, _ []overloadImpl, _ error) {
	switch len(s.overloadIdxs) {
	case 0:
		if err := defaultTypeCheck(ctx, s, false); err != nil {
			return false, nil, nil, err
		}
		return true, s.typedExprs, nil, nil

	case 1:
		idx := s.overloadIdxs[0]
		o := s.overloads[idx]
		p := o.params()
		for _, i := range s.constIdxs {
			des := p.GetAt(i)
			typ, err := s.exprs[i].TypeCheck(ctx, des)
			if err != nil {
				return false, s.typedExprs, nil, pgerror.Wrapf(
					err, pgcode.InvalidParameterValue,
					"error type checking constant value",
				)
			}
			if des != nil && !typ.ResolvedType().Equivalent(des) {
				//return false, nil, nil, errors.AssertionFailedf(
				//	"desired constant value type %s but set type %s",
				//	log.Safe(des), log.Safe(typ.ResolvedType()),
				//)
				return false, nil, nil, errors.AssertionFailedf(
					"desired constant value type %s but set type %s",
					des, typ.ResolvedType(),
				)
			}
			s.typedExprs[i] = typ
		}

		for _, i := range s.placeholderIdxs {
			des := p.GetAt(i)
			typ, err := s.exprs[i].TypeCheck(ctx, des)
			if err != nil {
				if des.IsAmbiguous() {
					return false, nil, nil, nil
				}
				return false, nil, nil, err
			}
			s.typedExprs[i] = typ
		}
		return true, s.typedExprs, s.overloads[idx : idx+1], nil

	default:
		return false, nil, nil, nil
	}
}

func formatCandidates(prefix string, candidates []overloadImpl) string {
	var buf bytes.Buffer