diff --git a/.github/workflows/build-and-test.yml b/.github/workflows/build-and-test.yml
new file mode 100644
index 0000000..2533199
--- /dev/null
+++ b/.github/workflows/build-and-test.yml
@@ -0,0 +1,67 @@
+name: Continuous Integration
+on:
+  push:
+  pull_request:
+  schedule:
+    - cron: '42 15 * * *'
+jobs:
+  build:
+    name: HHVM ${{matrix.hhvm}} - ${{matrix.os}}
+    strategy:
+      # Run tests on all OS's and HHVM versions, even if one fails
+      fail-fast: false
+      matrix:
+        os: [ ubuntu ]
+        hhvm:
+          - '4.62'
+          - latest
+          - nightly
+    runs-on: ${{matrix.os}}-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install Composer
+        run: .github/workflows/install-composer.sh --install-dir=${{runner.temp}}
+      - name: Install HHVM (apt)
+        if: matrix.os == 'ubuntu'
+        run: |
+          set -ex
+          export DEBIAN_FRONTEND=noninteractive
+          sudo apt-get update
+          sudo apt-get install -y software-properties-common apt-transport-https
+          sudo apt-key add .github/workflows/hhvm.gpg.key
+          if [ "${{matrix.hhvm}}" = "nightly" ]; then
+            sudo add-apt-repository https://dl.hhvm.com/ubuntu
+            sudo apt-get install -y hhvm-nightly
+          elif [ "${{matrix.hhvm}}" = "latest" ]; then
+            sudo add-apt-repository https://dl.hhvm.com/ubuntu
+            sudo apt-get install -y hhvm
+          else
+            DISTRO=$(lsb_release --codename --short)
+            sudo add-apt-repository \
+              "deb https://dl.hhvm.com/ubuntu ${DISTRO}-${{matrix.hhvm}} main"
+            sudo apt-get install -y hhvm
+          fi
+      - name: Install HHVM (brew)
+        if: matrix.os == 'macos'
+        run: |
+          brew tap hhvm/hhvm
+          if [ "${{matrix.hhvm}}" = "latest" ]; then
+            brew install hhvm
+          else
+            brew install hhvm-${{matrix.hhvm}}
+          fi
+      - name: Inspect HHVM and Hack versions
+        run: |
+          hhvm --version
+          hh_client --version
+      - name: Create branch for version alias
+        run: git checkout -b CI_current_pull_request
+      - name: Install project dependencies
+        run: php ${{runner.temp}}/composer.phar install
+      - name: Typecheck
+        run: hh_client
+      - name: Run tests
+        run: vendor/bin/hacktest tests/
+      - name: Run lint
+        if: matrix.hhvm != 'nightly'
+        run: vendor/bin/hhast-lint
diff --git a/.github/workflows/hhvm.gpg.key b/.github/workflows/hhvm.gpg.key
new file mode 100644
index 0000000..cd32c2f
--- /dev/null
+++ b/.github/workflows/hhvm.gpg.key
@@ -0,0 +1,36 @@
+-----BEGIN PGP PUBLIC KEY BLOCK-----
+Version: GnuPG v1
+
+mQINBFn8koEBEAC2tPtkphj8gZYHI9mTNUHfQalDo+MNWTGUTNB42asjhTNjipzM
+VSxjaZSl5cMLg5YCRuT0AbSIe529FH23yEElc03cGVGgoEnmXtE4+2v7Xa30wCGO
+5oUxKfbVatsxEs1y8QEr5Gt+CUFmsApOKgiZq0MsPYmFAuC9CbWdXYa8+E00bXOa
+cHCpe+GncCxQmExm7TlrUnURnf3RnNWSEkuPKED/aVggzxNVN6RgRRm4ssZJasM3
+TwoI1nVysO5jMfPClvupYscoktO44HBZzH2EeEdpjSV+toD3aZCbmWzXyZjogrFN
+j4k5Mme0Xqr4DvRPk5M9SxcQASsCQ8VTyu+ZBUG6zJbddLDEA1BMNIZOG5MyX58O
+zed255Q85SAyjHu8pltkfGLd56+MYsckpHaBPMFoCFM4iPcpXOlgcU96pdXJbrR2
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+tC1ISFZNIFBhY2thZ2UgU2lnbmluZyA8b3BlbnNvdXJjZStoaHZtQGZiLmNvbT6J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+RjbH/8Pi+U2l8Fm/SjHMZA6gcJteRHjTgjkxSAZ19MyA08YqahJafRUVDY9QhUJb
+FkHhptZRf9qRji3+Njhog6s8EGACJSEOwmngAViFVz+UUyOXY94yoHvb19meNecj
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+MM3vIX/Fc/kuuaCWi2ysyKf7jyi/RiVIAKuLbxAB8eHsyo2G5lA=
+=3DTP
+-----END PGP PUBLIC KEY BLOCK-----
diff --git a/.github/workflows/install-composer.sh b/.github/workflows/install-composer.sh
new file mode 100755
index 0000000..94d1d81
--- /dev/null
+++ b/.github/workflows/install-composer.sh
@@ -0,0 +1,19 @@
+#!/bin/sh
+
+# From https://getcomposer.org/doc/faqs/how-to-install-composer-programmatically.md
+
+EXPECTED_CHECKSUM="$(wget -q -O - https://composer.github.io/installer.sig)"
+php -r "copy('https://getcomposer.org/installer', 'composer-setup.php');"
+ACTUAL_CHECKSUM="$(php -r "echo hash_file('sha384', 'composer-setup.php');")"
+
+if [ "$EXPECTED_CHECKSUM" != "$ACTUAL_CHECKSUM" ]
+then
+    >&2 echo 'ERROR: Invalid installer checksum'
+    rm composer-setup.php
+    exit 1
+fi
+
+php composer-setup.php "$@"
+RESULT=$?
+rm composer-setup.php
+exit $RESULT
diff --git a/.travis.sh b/.travis.sh
deleted file mode 100755
index 02daa4b..0000000
--- a/.travis.sh
+++ /dev/null
@@ -1,21 +0,0 @@
-#!/bin/sh
-set -ex
-apt update -y
-DEBIAN_FRONTEND=noninteractive apt install -y php-cli zip unzip
-hhvm --version
-php --version
-
-(
-  cd $(mktemp -d)
-  curl https://getcomposer.org/installer | php -- --install-dir=/usr/local/bin --filename=composer
-)
-composer install
-
-hh_client
-
-vendor/bin/hacktest tests/
-# In prod, we have caching and no fallback handler. Check it.
-HH_FORCE_IS_DEV=0 vendor/bin/hacktest tests/
-if !(hhvm --version | grep -q -- -dev); then
-  vendor/bin/hhast-lint
-fi
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index 9ace7ad..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,14 +0,0 @@
-sudo: required
-language: generic
-services: docker
-env:
-- HHVM_VERSION=4.62-latest
-- HHVM_VERSION=latest
-- HHVM_VERSION=nightly
-install:
-- docker pull hhvm/hhvm:$HHVM_VERSION
-script:
-- docker run --rm -w /var/source -v $(pwd):/var/source hhvm/hhvm:$HHVM_VERSION ./.travis.sh
-notifications:
-  slack:
-    secure: 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
diff --git a/src/uri-patterns/UriPattern.php b/src/uri-patterns/UriPattern.php
index 2a9ce04..bb31416 100644
--- a/src/uri-patterns/UriPattern.php
+++ b/src/uri-patterns/UriPattern.php
@@ -30,16 +30,13 @@ final public function getParts(): ImmVector<UriPatternPart> {
   }
 
   final public function getParameters(): ImmVector<UriParameter> {
-    return $this
-      ->parts
-      ->filter($x ==> $x is UriParameter)
-      ->map(
-        $x ==> {
-          assert($x is UriParameter);
-          return $x;
-        },
-      )
-      ->immutable();
+    $out = Vector {};
+    foreach($this->parts as $part) {
+      if($part is UriParameter) {
+        $out->add($part);
+      }
+    }
+    return $out->immutable();
   }
 
   ///// Convenience Methods /////