src/Composer/DependencyResolver/Pool.php
public function whatProvides($name, ConstraintInterface $constraint = null, $mustMatchName = false, $bypassFilters = false)
    {
        if ($bypassFilters) {
            return $this->computeWhatProvides($name, $constraint, $mustMatchName, true);
        }

        $key = ((int) $mustMatchName).$constraint;
        if (isset($this->providerCache[$name][$key])) {
            return $this->providerCache[$name][$key];
        }

        return $this->providerCache[$name][$key] = $this->computeWhatProvides($name, $constraint, $mustMatchName, $bypassFilters);
    }
public function whatProvides($name, ConstraintInterface $constraint = null, $mustMatchName = false, $bypassFilters = false)
    {
        if ($bypassFilters) {
            return $this->computeWhatProvides($name, $constraint, $mustMatchName, true);
        }

        $key = ((int) $mustMatchName).$constraint;
        if (isset($this->providerCache[$name][$key])) {
            return $this->providerCache[$name][$key];
        }

        return $this->providerCache[$name][$key] = $this->computeWhatProvides($name, $constraint, $mustMatchName, $bypassFilters);
    }
Searches all packages providing the given package name and match the constraint

@param  string              $name          The package name to be searched for
@param  ConstraintInterface $constraint    A constraint that all returned
packages must match or null to return all
@param  bool                $mustMatchName Whether the name of returned packages
must match the given name
@param  bool                $bypassFilters If enabled, filterRequires and stability matching is ignored
@return PackageInterface[]  A set of packages