diff --git a/.buildbot.config.toml b/.buildbot.config.toml
index bed72399..e0b42f08 100644
--- a/.buildbot.config.toml
+++ b/.buildbot.config.toml
@@ -10,7 +10,6 @@ extended = false
 
 [llvm]
 assertions = true           # Turn on assertions in LLVM.
-use-linker = "gold"         # Uses less memory than ld.
 
 [install]
 prefix = "build/rustc_boehm"
diff --git a/.github/workflows/sdci.yml b/.github/workflows/sdci.yml
new file mode 100644
index 00000000..f20da180
--- /dev/null
+++ b/.github/workflows/sdci.yml
@@ -0,0 +1,11 @@
+on:
+  pull_request:
+  merge_group:
+
+# This is required to silence emails about the workflow having no jobs.
+# We simply define a dummy job that does nothing much.
+jobs:
+  dummy:
+    runs-on: ubuntu-latest
+    steps:
+      - run: /usr/bin/true
diff --git a/Cargo.lock b/Cargo.lock
index 7908d72f..84502b11 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4,24 +4,24 @@ version = 3
 
 [[package]]
 name = "aho-corasick"
-version = "0.7.20"
+version = "1.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cc936419f96fa211c1b9166887b38e5e40b19958e5b895be7c1f93adec7071ac"
+checksum = "b2969dcb958b36655471fc61f7e416fa76033bdd4bfed0678d8fee1e2d07a1f0"
 dependencies = [
  "memchr",
 ]
 
 [[package]]
 name = "anyhow"
-version = "1.0.68"
+version = "1.0.75"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2cb2f989d18dd141ab8ae82f64d1a8cdd37e0840f73a406896cf5e99502fab61"
+checksum = "a4668cab20f66d8d020e1fbc0ebe47217433c1b6c8f2040faf858554e394ace6"
 
 [[package]]
 name = "arrayvec"
-version = "0.7.2"
+version = "0.7.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8da52d66c7071e2e3fa2a1e5c6d088fec47b593032b254f5e980de8ea54454d6"
+checksum = "96d30a06541fbafbc7f82ed10c06164cfbd2c401138f6addd8404629c4b16711"
 
 [[package]]
 name = "autocfg"
@@ -44,11 +44,17 @@ version = "1.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
 
+[[package]]
+name = "bitflags"
+version = "2.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "327762f6e5a765692301e5bb513e0d9fef63be86bbc14528052b1cd3e6f03e07"
+
 [[package]]
 name = "bstr"
-version = "1.1.0"
+version = "1.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b45ea9b00a7b3f2988e9a65ad3917e62123c38dba709b666506207be96d1790b"
+checksum = "542f33a8835a0884b006a0c3df3dadd99c0c3f296ed26c2fdc8028e01ad6230c"
 dependencies = [
  "memchr",
  "serde",
@@ -68,9 +74,9 @@ checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 
 [[package]]
 name = "cfgrammar"
-version = "0.13.0"
+version = "0.13.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a2836ac78906e1f7c9462f161abfb843849d580775a08b62d099f0bca355c915"
+checksum = "41879646bd1fbd55efdb9e2c1ac85e63856ad951e4e14b2e3086374802a13e9b"
 dependencies = [
  "indexmap",
  "lazy_static",
@@ -82,9 +88,9 @@ dependencies = [
 
 [[package]]
 name = "dashmap"
-version = "5.4.0"
+version = "5.5.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "907076dfda823b0b36d2a1bb5f90c96660a5bbcd7729e10727f07858f22c4edc"
+checksum = "978747c1d849a7d2ee5e8adc0159961c48fb7e5db2f06af6723b80123bb53856"
 dependencies = [
  "cfg-if",
  "hashbrown",
@@ -94,48 +100,43 @@ dependencies = [
 ]
 
 [[package]]
-name = "either"
-version = "1.8.0"
+name = "deranged"
+version = "0.3.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "90e5c1c8368803113bf0c9584fc495a58b86dc8a29edbf8fe877d21d9507e797"
+checksum = "0f32d04922c60427da6f9fef14d042d9edddef64cb9d4ce0d64d0685fbeb1fd3"
+dependencies = [
+ "powerfmt",
+]
 
 [[package]]
-name = "enum-iterator"
-version = "1.2.0"
+name = "either"
+version = "1.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "91a4ec26efacf4aeff80887a175a419493cb6f8b5480d26387eb0bd038976187"
-dependencies = [
- "enum-iterator-derive",
-]
+checksum = "a26ae43d7bcc3b814de94796a5e736d4029efb0ee900c12e2d54c993ad1a1e07"
 
 [[package]]
-name = "enum-iterator-derive"
-version = "1.1.0"
+name = "equivalent"
+version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "828de45d0ca18782232dfb8f3ea9cc428e8ced380eb26a520baaacfc70de39ce"
-dependencies = [
- "proc-macro2 1.0.50",
- "quote 1.0.23",
- "syn 1.0.107",
-]
+checksum = "5443807d6dff69373d433ab9ef5378ad8df50ca6298caf15de6e52e24aaf54d5"
 
 [[package]]
 name = "filetime"
-version = "0.2.19"
+version = "0.2.22"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4e884668cd0c7480504233e951174ddc3b382f7c2666e3b7310b5c4e7b0c37f9"
+checksum = "d4029edd3e734da6fe05b6cd7bd2960760a616bd2ddd0d59a0124746d6272af0"
 dependencies = [
  "cfg-if",
  "libc",
- "redox_syscall",
+ "redox_syscall 0.3.5",
  "windows-sys",
 ]
 
 [[package]]
 name = "fm"
-version = "0.2.1"
+version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "671381339b1671872f5725caff3a4bd05be68a0d8adf2d8a7ff6c16395bbe35a"
+checksum = "21bcf4db620a804cf7e9d84fbcb5d4ac83a8c43396203b2507d62ea31814dfd4"
 dependencies = [
  "regex",
 ]
@@ -148,9 +149,9 @@ checksum = "3f9eec918d3f24069decb9af1554cad7c880e2da24a9afd88aca000531ab82c1"
 
 [[package]]
 name = "futures"
-version = "0.3.25"
+version = "0.3.29"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "38390104763dc37a5145a53c29c63c1290b5d316d6086ec32c293f6736051bb0"
+checksum = "da0290714b38af9b4a7b094b8a37086d1b4e61f2df9122c3cad2577669145335"
 dependencies = [
  "futures-channel",
  "futures-core",
@@ -163,9 +164,9 @@ dependencies = [
 
 [[package]]
 name = "futures-channel"
-version = "0.3.25"
+version = "0.3.29"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "52ba265a92256105f45b719605a571ffe2d1f0fea3807304b522c1d778f79eed"
+checksum = "ff4dd66668b557604244583e3e1e1eada8c5c2e96a6d0d6653ede395b78bbacb"
 dependencies = [
  "futures-core",
  "futures-sink",
@@ -173,15 +174,15 @@ dependencies = [
 
 [[package]]
 name = "futures-core"
-version = "0.3.25"
+version = "0.3.29"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "04909a7a7e4633ae6c4a9ab280aeb86da1236243a77b694a49eacd659a4bd3ac"
+checksum = "eb1d22c66e66d9d72e1758f0bd7d4fd0bee04cad842ee34587d68c07e45d088c"
 
 [[package]]
 name = "futures-executor"
-version = "0.3.25"
+version = "0.3.29"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7acc85df6714c176ab5edf386123fafe217be88c0840ec11f199441134a074e2"
+checksum = "0f4fb8693db0cf099eadcca0efe2a5a22e4550f98ed16aba6c48700da29597bc"
 dependencies = [
  "futures-core",
  "futures-task",
@@ -190,27 +191,27 @@ dependencies = [
 
 [[package]]
 name = "futures-io"
-version = "0.3.25"
+version = "0.3.29"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "00f5fb52a06bdcadeb54e8d3671f8888a39697dcb0b81b23b55174030427f4eb"
+checksum = "8bf34a163b5c4c52d0478a4d757da8fb65cabef42ba90515efee0f6f9fa45aaa"
 
 [[package]]
 name = "futures-sink"
-version = "0.3.25"
+version = "0.3.29"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "39c15cf1a4aa79df40f1bb462fb39676d0ad9e366c2a33b590d7c66f4f81fcf9"
+checksum = "e36d3378ee38c2a36ad710c5d30c2911d752cb941c00c72dbabfb786a7970817"
 
 [[package]]
 name = "futures-task"
-version = "0.3.25"
+version = "0.3.29"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2ffb393ac5d9a6eaa9d3fdf37ae2776656b706e200c8e16b1bdb227f5198e6ea"
+checksum = "efd193069b0ddadc69c46389b740bbccdd97203899b48d09c5f7969591d6bae2"
 
 [[package]]
 name = "futures-util"
-version = "0.3.25"
+version = "0.3.29"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "197676987abd2f9cadff84926f410af1c183608d36641465df73ae8211dc65d6"
+checksum = "a19526d624e703a3179b3d322efec918b6246ea0fa51d41124525f00f1cc8104"
 dependencies = [
  "futures-channel",
  "futures-core",
@@ -232,23 +233,11 @@ dependencies = [
  "unicode-width",
 ]
 
-[[package]]
-name = "getset"
-version = "0.1.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e45727250e75cc04ff2846a66397da8ef2b3db8e40e0cef4df67950a07621eb9"
-dependencies = [
- "proc-macro-error",
- "proc-macro2 1.0.50",
- "quote 1.0.23",
- "syn 1.0.107",
-]
-
 [[package]]
 name = "globset"
-version = "0.4.10"
+version = "0.4.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "029d74589adefde59de1a0c4f4732695c32805624aec7b68d91503d4dba79afc"
+checksum = "759c97c1e17c55525b57192c06a267cda0ac5210b222d6b82189a2338fa1c13d"
 dependencies = [
  "aho-corasick",
  "bstr",
@@ -259,18 +248,15 @@ dependencies = [
 
 [[package]]
 name = "hashbrown"
-version = "0.12.3"
+version = "0.14.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8a9ee70c43aaf417c914396645a0fa852624801b24ebb7ae78fe8272889ac888"
+checksum = "f93e7192158dbcda357bdec5fb5788eebf8bbac027f3f33e719d29135ae84156"
 
 [[package]]
 name = "hermit-abi"
-version = "0.2.6"
+version = "0.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ee512640fe35acbfb4bb779db6f0d80704c2cacfa2e39b601ef3e3f47d1ae4c7"
-dependencies = [
- "libc",
-]
+checksum = "d77f7ec81a6d05a3abb01ab6eb7590f6083d08449fe5a1c8b1e620283546ccb7"
 
 [[package]]
 name = "ignore"
@@ -291,11 +277,11 @@ dependencies = [
 
 [[package]]
 name = "indexmap"
-version = "1.9.2"
+version = "2.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1885e79c1fc4b10f0e172c475f458b7f7b93061064d98c3293e98c5ba0c8b399"
+checksum = "d530e1a18b1cb4c484e6e34556a0d948706958449fca0cab753d649f2bce3d1f"
 dependencies = [
- "autocfg",
+ "equivalent",
  "hashbrown",
 ]
 
@@ -310,15 +296,15 @@ dependencies = [
 
 [[package]]
 name = "itoa"
-version = "1.0.5"
+version = "1.0.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fad582f4b9e86b6caa621cabeb0963332d92eea04729ab12892c2533951e6440"
+checksum = "af150ab688ff2122fcef229be89cb50dd66af9e01a4ff320cc137eecc9bacc38"
 
 [[package]]
 name = "lang_tester"
-version = "0.7.1"
+version = "0.7.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d63df63b7380a561f2c38b0a67ebe3a24b87ff2928391d0b5f8f3cfd39fe112c"
+checksum = "5f7fe9f105796d077b01479ccc498e5a88ec54600a404f82aacb6cdbd05012d8"
 dependencies = [
  "fm",
  "getopts",
@@ -338,15 +324,26 @@ checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
 
 [[package]]
 name = "libc"
-version = "0.2.139"
+version = "0.2.150"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "201de327520df007757c1f0adce6e827fe8562fbc28bfd9c15571c66ca1f5f79"
+checksum = "89d92a4743f9a61002fae18374ed11e7973f530cb3a3255fb354818118b2203c"
+
+[[package]]
+name = "libredox"
+version = "0.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3af92c55d7d839293953fcd0fda5ecfe93297cfde6ffbdec13b41d99c0ba6607"
+dependencies = [
+ "bitflags 2.4.1",
+ "libc",
+ "redox_syscall 0.4.1",
+]
 
 [[package]]
 name = "lock_api"
-version = "0.4.9"
+version = "0.4.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "435011366fe56583b16cf956f9df0095b405b82d76425bc8981c0e22e60ec4df"
+checksum = "3c168f8615b12bc01f9c17e2eb0cc07dcae1940121185446edc3744920e8ef45"
 dependencies = [
  "autocfg",
  "scopeguard",
@@ -354,36 +351,33 @@ dependencies = [
 
 [[package]]
 name = "log"
-version = "0.4.17"
+version = "0.4.20"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "abb12e687cfb44aa40f41fc3978ef76448f9b6038cad6aef4259d3c095a2382e"
-dependencies = [
- "cfg-if",
-]
+checksum = "b5e6163cb8c49088c2c36f57875e58ccd8c87c7427f7fbd50ea6710b2f3f2e8f"
 
 [[package]]
 name = "lrlex"
-version = "0.13.0"
+version = "0.13.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b5b7775c88626ab4f91de188a14deb71e4149f89efcd8ee3d1b779cad4b946d3"
+checksum = "4d3c956ecfc913cb0e89575c5dd74d2558ec6e12c18f23baabc2985dc48ead28"
 dependencies = [
  "cfgrammar",
  "getopts",
  "lazy_static",
  "lrpar",
  "num-traits",
- "quote 1.0.23",
+ "quote 1.0.33",
  "regex",
- "regex-syntax",
+ "regex-syntax 0.7.5",
  "serde",
  "vergen",
 ]
 
 [[package]]
 name = "lrpar"
-version = "0.13.0"
+version = "0.13.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ceec66ff63c6d3e376acab385dfbd2795ed96e0b834464ec949a51d536d2f1df"
+checksum = "c3f2acdd7023dc9f0eb51b13a615477c245519f593537667116874d2c699972d"
 dependencies = [
  "bincode",
  "cactus",
@@ -403,9 +397,9 @@ dependencies = [
 
 [[package]]
 name = "lrtable"
-version = "0.13.0"
+version = "0.13.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6f2e2b6439a4ba90b2d55a64bb4aa7c606485218473db67402c45829e1bbcda7"
+checksum = "310933a066b41ed437844d548c5972b02b407e63a8254d08204082a05f7a1b34"
 dependencies = [
  "cfgrammar",
  "fnv",
@@ -417,14 +411,14 @@ dependencies = [
 
 [[package]]
 name = "memchr"
-version = "2.5.0"
+version = "2.6.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2dffe52ecf27772e601905b7522cb4ef790d2cc203488bbd0e2fe85fcb74566d"
+checksum = "f665ee40bc4a3c5590afb1e9677db74a508659dfd71e126420da8274909a0167"
 
 [[package]]
 name = "natrob"
 version = "0.1.0"
-source = "git+https://github.com/softdevteam/natrob#fd99aad6dc023fd078ad033a5beca4b6a9bd021e"
+source = "git+https://github.com/softdevteam/natrob#b3133f50c6072c57a83151150d57c7bd54e02c13"
 dependencies = [
  "quote 0.6.13",
  "syn 0.15.44",
@@ -432,9 +426,9 @@ dependencies = [
 
 [[package]]
 name = "num-bigint"
-version = "0.4.3"
+version = "0.4.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f93ab6289c7b344a8a9f60f88d80aa20032336fe78da341afc91c8a2341fc75f"
+checksum = "608e7659b5c3d7cba262d894801b9ec9d00de989e8a82bd4bef91d08da45cdc0"
 dependencies = [
  "autocfg",
  "num-integer",
@@ -453,18 +447,18 @@ dependencies = [
 
 [[package]]
 name = "num-traits"
-version = "0.2.15"
+version = "0.2.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "578ede34cf02f8924ab9447f50c28075b4d3e5b269972345e7e0372b38c6cdcd"
+checksum = "39e3200413f237f41ab11ad6d161bc7239c84dcb631773ccd7de3dfe4b5c267c"
 dependencies = [
  "autocfg",
 ]
 
 [[package]]
 name = "num_cpus"
-version = "1.15.0"
+version = "1.16.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0fac9e2da13b5eb447a6ce3d392f23a29d8694bff781bf03a16cd9ac8697593b"
+checksum = "4161fcb6d602d4d2081af7c3a45852d875a03dd337a6bfdd6e06407b61342a43"
 dependencies = [
  "hermit-abi",
  "libc",
@@ -472,23 +466,32 @@ dependencies = [
 
 [[package]]
 name = "num_enum"
-version = "0.5.7"
+version = "0.5.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cf5395665662ef45796a4ff5486c5d41d29e0c09640af4c5f17fd94ee2c119c9"
+checksum = "1f646caf906c20226733ed5b1374287eb97e3c2a5c227ce668c1f2ce20ae57c9"
 dependencies = [
  "num_enum_derive",
 ]
 
 [[package]]
 name = "num_enum_derive"
-version = "0.5.7"
+version = "0.5.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3b0498641e53dd6ac1a4f22547548caa6864cc4933784319cd1775271c5a46ce"
+checksum = "dcbff9bc912032c62bf65ef1d5aea88983b420f4f839db1e9b0c281a25c9c799"
 dependencies = [
  "proc-macro-crate",
- "proc-macro2 1.0.50",
- "quote 1.0.23",
- "syn 1.0.107",
+ "proc-macro2 1.0.69",
+ "quote 1.0.33",
+ "syn 1.0.109",
+]
+
+[[package]]
+name = "num_threads"
+version = "0.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2819ce041d2ee131036f4fc9d6ae7ae125a3a40e97ba64d04fe799ad9dabbb44"
+dependencies = [
+ "libc",
 ]
 
 [[package]]
@@ -499,9 +502,9 @@ checksum = "b8f8bdf33df195859076e54ab11ee78a1b208382d3a26ec40d142ffc1ecc49ef"
 
 [[package]]
 name = "once_cell"
-version = "1.17.0"
+version = "1.18.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6f61fba1741ea2b3d6a1e3178721804bb716a68a6aeba1149b5d52e3d464ea66"
+checksum = "dd8b5dd2ae5ed71462c540258bedcb51965123ad7e7ccf4b9a8cafaa4a63576d"
 
 [[package]]
 name = "packedvec"
@@ -525,32 +528,22 @@ dependencies = [
 
 [[package]]
 name = "parking_lot_core"
-version = "0.9.6"
+version = "0.9.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ba1ef8814b5c993410bb3adfad7a5ed269563e4a2f90c41f5d85be7fb47133bf"
+checksum = "4c42a9226546d68acdd9c0a280d17ce19bfe27a46bf68784e4066115788d008e"
 dependencies = [
  "cfg-if",
  "libc",
- "redox_syscall",
+ "redox_syscall 0.4.1",
  "smallvec",
- "windows-sys",
-]
-
-[[package]]
-name = "pest"
-version = "2.5.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4257b4a04d91f7e9e6290be5d3da4804dd5784fafde3a497d73eb2b4a158c30a"
-dependencies = [
- "thiserror",
- "ucd-trie",
+ "windows-targets",
 ]
 
 [[package]]
 name = "pin-project-lite"
-version = "0.2.9"
+version = "0.2.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e0a7ae3ac2f1173085d398531c705756c94a4c56843785df85a60c1a0afac116"
+checksum = "8afb450f006bf6385ca15ef45d71d2288452bc3683ce2e2cacc0d18e4be60b58"
 
 [[package]]
 name = "pin-utils"
@@ -559,38 +552,19 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8b870d8c151b6f2fb93e84a13146138f05d02ed11c7e7c54f8826aaaf7c9f184"
 
 [[package]]
-name = "proc-macro-crate"
-version = "1.2.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "eda0fc3b0fb7c975631757e14d9049da17374063edb6ebbcbc54d880d4fe94e9"
-dependencies = [
- "once_cell",
- "thiserror",
- "toml",
-]
-
-[[package]]
-name = "proc-macro-error"
-version = "1.0.4"
+name = "powerfmt"
+version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "da25490ff9892aab3fcf7c36f08cfb902dd3e71ca0f9f9517bea02a73a5ce38c"
-dependencies = [
- "proc-macro-error-attr",
- "proc-macro2 1.0.50",
- "quote 1.0.23",
- "syn 1.0.107",
- "version_check",
-]
+checksum = "439ee305def115ba05938db6eb1644ff94165c5ab5e9420d1c1bcedbba909391"
 
 [[package]]
-name = "proc-macro-error-attr"
-version = "1.0.4"
+name = "proc-macro-crate"
+version = "1.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a1be40180e52ecc98ad80b184934baf3d0d29f979574e439af5a55274b35f869"
+checksum = "7f4c021e1093a56626774e81216a4ce732a735e5bad4868a03f3ed65ca0c3919"
 dependencies = [
- "proc-macro2 1.0.50",
- "quote 1.0.23",
- "version_check",
+ "once_cell",
+ "toml_edit",
 ]
 
 [[package]]
@@ -604,9 +578,9 @@ dependencies = [
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.50"
+version = "1.0.69"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6ef7d57beacfaf2d8aee5937dab7b7f28de3cb8b1828479bb5de2a7106f2bae2"
+checksum = "134c189feb4956b20f6f547d2cf727d4c0fe06722b20a0eec87ed445a97f92da"
 dependencies = [
  "unicode-ident",
 ]
@@ -622,47 +596,71 @@ dependencies = [
 
 [[package]]
 name = "quote"
-version = "1.0.23"
+version = "1.0.33"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8856d8364d252a14d474036ea1358d63c9e6965c8e5c1885c18f73d70bff9c7b"
+checksum = "5267fca4496028628a95160fc423a33e8b2e6af8a5302579e322e4b520293cae"
 dependencies = [
- "proc-macro2 1.0.50",
+ "proc-macro2 1.0.69",
 ]
 
 [[package]]
 name = "redox_syscall"
-version = "0.2.16"
+version = "0.3.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fb5a58c1855b4b6819d59012155603f0b22ad30cad752600aadfcb695265519a"
+checksum = "567664f262709473930a4bf9e51bf2ebf3348f2e748ccc50dea20646858f8f29"
 dependencies = [
- "bitflags",
+ "bitflags 1.3.2",
 ]
 
 [[package]]
-name = "redox_termios"
-version = "0.1.2"
+name = "redox_syscall"
+version = "0.4.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8440d8acb4fd3d277125b4bd01a6f38aee8d814b3b5fc09b3f2b825d37d3fe8f"
+checksum = "4722d768eff46b75989dd134e5c353f0d6296e5aaa3132e776cbdb56be7731aa"
 dependencies = [
- "redox_syscall",
+ "bitflags 1.3.2",
 ]
 
+[[package]]
+name = "redox_termios"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "20145670ba436b55d91fc92d25e71160fbfbdd57831631c8d7d36377a476f1cb"
+
 [[package]]
 name = "regex"
-version = "1.7.1"
+version = "1.10.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "380b951a9c5e80ddfd6136919eef32310721aa4aacd4889a8d39124b026ab343"
+dependencies = [
+ "aho-corasick",
+ "memchr",
+ "regex-automata",
+ "regex-syntax 0.8.2",
+]
+
+[[package]]
+name = "regex-automata"
+version = "0.4.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "48aaa5748ba571fb95cd2c85c09f629215d3a6ece942baa100950af03a34f733"
+checksum = "5f804c7828047e88b2d32e2d7fe5a105da8ee3264f01902f796c8e067dc2483f"
 dependencies = [
  "aho-corasick",
  "memchr",
- "regex-syntax",
+ "regex-syntax 0.8.2",
 ]
 
 [[package]]
 name = "regex-syntax"
-version = "0.6.28"
+version = "0.7.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "456c603be3e8d448b072f410900c09faf164fbce2d480456f50eea6e25f9c848"
+checksum = "dbb5fb1acd8a1a18b3dd5be62d25485eb770e05afb408a9627d14d451bae12da"
+
+[[package]]
+name = "regex-syntax"
+version = "0.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c08c74e62047bb2de4ff487b251e4a92e24f48745648451635cec7d591162d9f"
 
 [[package]]
 name = "rerun_except"
@@ -675,24 +673,24 @@ dependencies = [
 
 [[package]]
 name = "rustc_version"
-version = "0.3.3"
+version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f0dfe2087c51c460008730de8b57e6a320782fbfb312e1f4d520e6c6fae155ee"
+checksum = "bfa0f585226d2e68097d4f95d113b15b83a82e819ab25717ec0590d9584ef366"
 dependencies = [
  "semver",
 ]
 
 [[package]]
 name = "rustversion"
-version = "1.0.11"
+version = "1.0.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5583e89e108996506031660fe09baa5011b9dd0341b89029313006d1fb508d70"
+checksum = "7ffc183a10b4478d04cbbbfc96d0873219d962dd5accaff2ffbd4ceb7df837f4"
 
 [[package]]
 name = "ryu"
-version = "1.0.12"
+version = "1.0.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7b4b9743ed687d4b4bcedf9ff5eaa7398495ae14e61cba0a295704edbc7decde"
+checksum = "1ad4cc8da4ef723ed60bced201181d83791ad433213d8c24efffda1eec85d741"
 
 [[package]]
 name = "same-file"
@@ -705,46 +703,34 @@ dependencies = [
 
 [[package]]
 name = "scopeguard"
-version = "1.1.0"
+version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
+checksum = "94143f37725109f92c262ed2cf5e59bce7498c01bcc1502d7b9afe439a4e9f49"
 
 [[package]]
 name = "semver"
-version = "0.11.0"
+version = "1.0.20"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f301af10236f6df4160f7c3f04eec6dbc70ace82d23326abad5edee88801c6b6"
-dependencies = [
- "semver-parser",
-]
-
-[[package]]
-name = "semver-parser"
-version = "0.10.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "00b0bef5b7f9e0df16536d3961cfb6e84331c065b4066afb39768d0e319411f7"
-dependencies = [
- "pest",
-]
+checksum = "836fa6a3e1e547f9a2c4040802ec865b5d85f4014efe00555d7090a3dcaa1090"
 
 [[package]]
 name = "serde"
-version = "1.0.152"
+version = "1.0.192"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bb7d1f0d3021d347a83e556fc4683dea2ea09d87bccdf88ff5c12545d89d5efb"
+checksum = "bca2a08484b285dcb282d0f67b26cadc0df8b19f8c12502c13d966bf9482f001"
 dependencies = [
  "serde_derive",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.152"
+version = "1.0.192"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "af487d118eecd09402d70a5d72551860e788df87b464af30e5ea6a38c75c541e"
+checksum = "d6c7207fbec9faa48073f3e3074cbe553af6ea512d7c21ba46e434e70ea9fbc1"
 dependencies = [
- "proc-macro2 1.0.50",
- "quote 1.0.23",
- "syn 1.0.107",
+ "proc-macro2 1.0.69",
+ "quote 1.0.33",
+ "syn 2.0.39",
 ]
 
 [[package]]
@@ -767,25 +753,25 @@ version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "079a83df15f85d89a68d64ae1238f142f172b1fa915d0d76b26a7cba1b659a69"
 dependencies = [
- "proc-macro2 1.0.50",
- "quote 1.0.23",
- "syn 1.0.107",
+ "proc-macro2 1.0.69",
+ "quote 1.0.33",
+ "syn 1.0.109",
 ]
 
 [[package]]
 name = "slab"
-version = "0.4.7"
+version = "0.4.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4614a76b2a8be0058caa9dbbaf66d988527d86d003c11a94fbd335d7661edcef"
+checksum = "8f92a496fb766b417c996b9c5e57daf2f7ad3b0bebe1ccfca4856390e3d3bb67"
 dependencies = [
  "autocfg",
 ]
 
 [[package]]
 name = "smallvec"
-version = "1.10.0"
+version = "1.11.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a507befe795404456341dfab10cef66ead4c041f62b8b11bbb92bffe5d0953e0"
+checksum = "4dccd0940a2dcdf68d092b8cbab7dc0ad8fa938bf95787e1b916b0e3d0e8e970"
 
 [[package]]
 name = "smartstring"
@@ -829,62 +815,54 @@ dependencies = [
 
 [[package]]
 name = "syn"
-version = "1.0.107"
+version = "1.0.109"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1f4064b5b16e03ae50984a5a8ed5d4f8803e6bc1fd170a3cda91a1be4b18e3f5"
+checksum = "72b64191b275b66ffe2469e8af2c1cfe3bafa67b529ead792a6d0160888b4237"
 dependencies = [
- "proc-macro2 1.0.50",
- "quote 1.0.23",
+ "proc-macro2 1.0.69",
+ "quote 1.0.33",
+ "unicode-ident",
+]
+
+[[package]]
+name = "syn"
+version = "2.0.39"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "23e78b90f2fcf45d3e842032ce32e3f2d1545ba6636271dcbf24fa306d87be7a"
+dependencies = [
+ "proc-macro2 1.0.69",
+ "quote 1.0.33",
  "unicode-ident",
 ]
 
 [[package]]
 name = "termcolor"
-version = "1.2.0"
+version = "1.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "be55cf8942feac5c765c2c993422806843c9a9a45d4d5c407ad6dd2ea95eb9b6"
+checksum = "6093bad37da69aab9d123a8091e4be0aa4a03e4d601ec641c327398315f62b64"
 dependencies = [
  "winapi-util",
 ]
 
 [[package]]
 name = "termion"
-version = "2.0.1"
+version = "2.0.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "659c1f379f3408c7e5e84c7d0da6d93404e3800b6b9d063ba24436419302ec90"
+checksum = "c4648c7def6f2043b2568617b9f9b75eae88ca185dbc1f1fda30e95a85d49d7d"
 dependencies = [
  "libc",
+ "libredox",
  "numtoa",
- "redox_syscall",
  "redox_termios",
 ]
 
-[[package]]
-name = "thiserror"
-version = "1.0.38"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6a9cd18aa97d5c45c6603caea1da6628790b37f7a34b6ca89522331c5180fed0"
-dependencies = [
- "thiserror-impl",
-]
-
-[[package]]
-name = "thiserror-impl"
-version = "1.0.38"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1fb327af4685e4d03fa8cbcf1716380da910eeb2bb8be417e7f9fd3fb164f36f"
-dependencies = [
- "proc-macro2 1.0.50",
- "quote 1.0.23",
- "syn 1.0.107",
-]
-
 [[package]]
 name = "thread_local"
-version = "1.1.4"
+version = "1.1.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5516c27b78311c50bf42c071425c560ac799b11c30b31f87e3081965fe5e0180"
+checksum = "3fdd6f064ccff2d6567adcb3873ca630700f00b5ad3f060c25b5dcfd9a4ce152"
 dependencies = [
+ "cfg-if",
  "once_cell",
 ]
 
@@ -899,11 +877,15 @@ dependencies = [
 
 [[package]]
 name = "time"
-version = "0.3.17"
+version = "0.3.30"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a561bf4617eebd33bca6434b988f39ed798e527f51a1e797d0ee4f61c0a38376"
+checksum = "c4a34ab300f2dee6e562c10a046fc05e358b29f9bf92277f30c3c8d82275f6f5"
 dependencies = [
+ "deranged",
  "itoa",
+ "libc",
+ "num_threads",
+ "powerfmt",
  "serde",
  "time-core",
  "time-macros",
@@ -911,45 +893,47 @@ dependencies = [
 
 [[package]]
 name = "time-core"
-version = "0.1.0"
+version = "0.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2e153e1f1acaef8acc537e68b44906d2db6436e2b35ac2c6b42640fff91f00fd"
+checksum = "ef927ca75afb808a4d64dd374f00a2adf8d0fcff8e7b184af886c3c87ec4a3f3"
 
 [[package]]
 name = "time-macros"
-version = "0.2.6"
+version = "0.2.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d967f99f534ca7e495c575c62638eebc2898a8c84c119b89e250477bc4ba16b2"
+checksum = "4ad70d68dba9e1f8aceda7aa6711965dfec1cac869f311a51bd08b3a2ccbce20"
 dependencies = [
  "time-core",
 ]
 
 [[package]]
-name = "toml"
-version = "0.5.10"
+name = "toml_datetime"
+version = "0.6.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1333c76748e868a4d9d1017b5ab53171dfd095f70c712fdb4653a406547f598f"
-dependencies = [
- "serde",
-]
+checksum = "3550f4e9685620ac18a50ed434eb3aec30db8ba93b0287467bca5826ea25baf1"
 
 [[package]]
-name = "ucd-trie"
-version = "0.1.5"
+name = "toml_edit"
+version = "0.19.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9e79c4d996edb816c91e4308506774452e55e95c3c9de07b6729e17e15a5ef81"
+checksum = "1b5bb770da30e5cbfde35a2d7b9b8a2c4b8ef89548a7a6aeab5c9a576e3e7421"
+dependencies = [
+ "indexmap",
+ "toml_datetime",
+ "winnow",
+]
 
 [[package]]
 name = "unicode-ident"
-version = "1.0.6"
+version = "1.0.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "84a22b9f218b40614adcb3f4ff08b703773ad44fa9423e4e0d346d5db86e4ebc"
+checksum = "3354b9ac3fae1ff6755cb6db53683adb661634f67557942dea4facebec0fee4b"
 
 [[package]]
 name = "unicode-width"
-version = "0.1.10"
+version = "0.1.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c0edd1e5b14653f783770bce4a4dabb4a5108a5370a5f5d8cfe8710c361f6c8b"
+checksum = "e51733f11c9c4f72aa0c160008246859e340b00807569a0da0e7a1079b27ba85"
 
 [[package]]
 name = "unicode-xid"
@@ -959,16 +943,12 @@ checksum = "fc72304796d0818e357ead4e000d19c9c174ab23dc11093ac919054d20a6a7fc"
 
 [[package]]
 name = "vergen"
-version = "7.5.0"
+version = "8.2.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "571b69f690c855821462709b6f41d42ceccc316fbd17b60bd06d06928cfe6a99"
+checksum = "1290fd64cc4e7d3c9b07d7f333ce0ce0007253e32870e632624835cc80b83939"
 dependencies = [
  "anyhow",
- "cfg-if",
- "enum-iterator",
- "getset",
  "rustversion",
- "thiserror",
  "time",
 ]
 
@@ -980,9 +960,9 @@ checksum = "49874b5167b65d7193b8aba1567f5c7d93d001cafc34600cee003eda787e483f"
 
 [[package]]
 name = "vob"
-version = "3.0.2"
+version = "3.0.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cbdb3eee5dd38a27129832bca4a3171888e699a6ac36de86547975466997986f"
+checksum = "c058f4c41e71a043c67744cb76dcc1ae63ece328c1732a72489ccccc2dec23e6"
 dependencies = [
  "num-traits",
  "rustc_version",
@@ -1000,12 +980,11 @@ dependencies = [
 
 [[package]]
 name = "walkdir"
-version = "2.3.2"
+version = "2.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "808cf2735cd4b6866113f648b791c6adc5714537bc222d9347bb203386ffda56"
+checksum = "d71d857dc86794ca4c280d616f7da00d2dbfd8cd788846559a6813e6aa4b54ee"
 dependencies = [
  "same-file",
- "winapi",
  "winapi-util",
 ]
 
@@ -1027,9 +1006,9 @@ checksum = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
 
 [[package]]
 name = "winapi-util"
-version = "0.1.5"
+version = "0.1.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "70ec6ce85bb158151cae5e5c87f95a8e97d2c0c4b001223f33a334e3ce5de178"
+checksum = "f29e6f9198ba0d26b4c9f07dbe6f9ed633e1f3d5b8b414090084349e46a52596"
 dependencies = [
  "winapi",
 ]
@@ -1042,9 +1021,18 @@ checksum = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
 
 [[package]]
 name = "windows-sys"
-version = "0.42.0"
+version = "0.48.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "677d2418bec65e3338edb076e806bc1ec15693c5d0104683f2efe857f61056a9"
+dependencies = [
+ "windows-targets",
+]
+
+[[package]]
+name = "windows-targets"
+version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5a3e1820f08b8513f676f7ab6c1f99ff312fb97b553d30ff4dd86f9f15728aa7"
+checksum = "9a2fa6e2155d7247be68c096456083145c183cbbbc2764150dda45a87197940c"
 dependencies = [
  "windows_aarch64_gnullvm",
  "windows_aarch64_msvc",
@@ -1057,45 +1045,54 @@ dependencies = [
 
 [[package]]
 name = "windows_aarch64_gnullvm"
-version = "0.42.1"
+version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8c9864e83243fdec7fc9c5444389dcbbfd258f745e7853198f365e3c4968a608"
+checksum = "2b38e32f0abccf9987a4e3079dfb67dcd799fb61361e53e2882c3cbaf0d905d8"
 
 [[package]]
 name = "windows_aarch64_msvc"
-version = "0.42.1"
+version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4c8b1b673ffc16c47a9ff48570a9d85e25d265735c503681332589af6253c6c7"
+checksum = "dc35310971f3b2dbbf3f0690a219f40e2d9afcf64f9ab7cc1be722937c26b4bc"
 
 [[package]]
 name = "windows_i686_gnu"
-version = "0.42.1"
+version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "de3887528ad530ba7bdbb1faa8275ec7a1155a45ffa57c37993960277145d640"
+checksum = "a75915e7def60c94dcef72200b9a8e58e5091744960da64ec734a6c6e9b3743e"
 
 [[package]]
 name = "windows_i686_msvc"
-version = "0.42.1"
+version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bf4d1122317eddd6ff351aa852118a2418ad4214e6613a50e0191f7004372605"
+checksum = "8f55c233f70c4b27f66c523580f78f1004e8b5a8b659e05a4eb49d4166cca406"
 
 [[package]]
 name = "windows_x86_64_gnu"
-version = "0.42.1"
+version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c1040f221285e17ebccbc2591ffdc2d44ee1f9186324dd3e84e99ac68d699c45"
+checksum = "53d40abd2583d23e4718fddf1ebec84dbff8381c07cae67ff7768bbf19c6718e"
 
 [[package]]
 name = "windows_x86_64_gnullvm"
-version = "0.42.1"
+version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "628bfdf232daa22b0d64fdb62b09fcc36bb01f05a3939e20ab73aaf9470d0463"
+checksum = "0b7b52767868a23d5bab768e390dc5f5c55825b6d30b86c844ff2dc7414044cc"
 
 [[package]]
 name = "windows_x86_64_msvc"
-version = "0.42.1"
+version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "447660ad36a13288b1db4d4248e857b510e8c3a225c822ba4fb748c0aafecffd"
+checksum = "ed94fce61571a4006852b7389a063ab983c02eb1bb37b47f8272ce92d06d9538"
+
+[[package]]
+name = "winnow"
+version = "0.5.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "829846f3e3db426d4cee4510841b71a8e58aa2a76b1132579487ae430ccd9c7b"
+dependencies = [
+ "memchr",
+]
 
 [[package]]
 name = "yksom"
diff --git a/bors.toml b/bors.toml
deleted file mode 100644
index 2084ca33..00000000
--- a/bors.toml
+++ /dev/null
@@ -1,8 +0,0 @@
-status = ["buildbot/buildbot-build-script"]
-
-timeout_sec = 1800 # 30 minutes
-
-# Have bors delete auto-merged branches
-delete_merged_branches = true
-
-cut_body_after = ""
diff --git a/src/lib/compiler/ast_to_instrs.rs b/src/lib/compiler/ast_to_instrs.rs
index 60ff93ac..b462c587 100644
--- a/src/lib/compiler/ast_to_instrs.rs
+++ b/src/lib/compiler/ast_to_instrs.rs
@@ -8,7 +8,7 @@ use itertools::Itertools;
 use lrlex::{DefaultLexerTypes, LRNonStreamingLexer};
 use lrpar::{NonStreamingLexer, Span};
 use num_bigint::BigInt;
-use smartstring::alias::String as SmartString;
+
 use std::gc::{Gc, NonFinalizable};
 
 use crate::{
@@ -31,10 +31,10 @@ const CLOSURE_RETURN_VAR: &str = "$$closurereturn$$";
 pub struct Compiler<'a, 'input> {
     lexer: &'a LRNonStreamingLexer<'a, 'input, DefaultLexerTypes<StorageT>>,
     path: &'a Path,
-    upvars_stack: Vec<Vec<(SmartString, UpVarDef)>>,
+    upvars_stack: Vec<Vec<(String, UpVarDef)>>,
     /// The stack of local variables at the current point of evaluation. Maps variable names to
     /// `(captured, var idx)`.
-    locals_stack: Vec<HashMap<SmartString, (bool, usize)>>,
+    locals_stack: Vec<HashMap<String, (bool, usize)>>,
     blocks_stack: Vec<Vec<Gc<Function>>>,
     /// Since SOM's "^" operator returns from the enclosed method, we need to track whether we are
     /// in a closure -- and, if so, how many nested closures we are inside at the current point of
@@ -58,7 +58,7 @@ impl<'a, 'input> Compiler<'a, 'input> {
         lexer: &LRNonStreamingLexer<DefaultLexerTypes<StorageT>>,
         path: &Path,
         astcls: &ast::Class,
-    ) -> Result<(SmartString, Val), String> {
+    ) -> Result<(String, Val), String> {
         let mut compiler = Compiler {
             lexer,
             path,
@@ -68,7 +68,7 @@ impl<'a, 'input> Compiler<'a, 'input> {
             closure_depth: 0,
         };
 
-        let name = SmartString::from(lexer.span_str(astcls.name));
+        let name = String::from(lexer.span_str(astcls.name));
         let (supercls_val, supercls_meta_val) = if name.as_str() != "Object" {
             let supercls_val = if let Some(n) = astcls.supername.map(|x| lexer.span_str(x)) {
                 match vm.load_class(n) {
@@ -159,7 +159,7 @@ impl<'a, 'input> Compiler<'a, 'input> {
         &mut self,
         vm: &mut VM,
         lexer: &'a LRNonStreamingLexer<DefaultLexerTypes<StorageT>>,
-        name: SmartString,
+        name: String,
         supercls_val: Val,
         ast_inst_vars: &[Span],
         ast_methods: &[ast::Method],
@@ -190,7 +190,7 @@ impl<'a, 'input> Compiler<'a, 'input> {
         };
         for var in ast_inst_vars {
             let vars_len = inst_vars.len();
-            let n = SmartString::from(lexer.span_str(*var));
+            let n = String::from(lexer.span_str(*var));
             match inst_vars.entry(n) {
                 hash_map::Entry::Occupied(_) => {
                     return Err(vec![(
@@ -233,7 +233,7 @@ impl<'a, 'input> Compiler<'a, 'input> {
         let inst_vars_map = self.locals_stack[0]
             .iter()
             .map(|(k, v)| (k.clone(), v.1))
-            .collect::<HashMap<SmartString, usize>>();
+            .collect::<HashMap<String, usize>>();
         self.locals_stack.pop();
         if !errs.is_empty() {
             return Err(errs);
@@ -257,27 +257,21 @@ impl<'a, 'input> Compiler<'a, 'input> {
         Ok(cls_val)
     }
 
-    fn c_method(
-        &mut self,
-        vm: &mut VM,
-        astmeth: &ast::Method,
-    ) -> CompileResult<(SmartString, Val)> {
+    fn c_method(&mut self, vm: &mut VM, astmeth: &ast::Method) -> CompileResult<(String, Val)> {
         let (name, args) = match astmeth.name {
             ast::MethodName::BinaryOp(op, arg) => {
                 let arg_v = match arg {
                     Some(l) => vec![l],
                     None => vec![],
                 };
-                ((op, SmartString::from(self.lexer.span_str(op))), arg_v)
-            }
-            ast::MethodName::Id(span) => {
-                ((span, SmartString::from(self.lexer.span_str(span))), vec![])
+                ((op, String::from(self.lexer.span_str(op))), arg_v)
             }
+            ast::MethodName::Id(span) => ((span, String::from(self.lexer.span_str(span))), vec![]),
             ast::MethodName::Keywords(ref pairs) => {
                 let name = pairs
                     .iter()
                     .map(|x| self.lexer.span_str(x.0))
-                    .collect::<SmartString>();
+                    .collect::<String>();
                 let args = pairs.iter().map(|x| x.1).collect::<Vec<_>>();
                 ((pairs[0].0, name), args)
             }
@@ -444,10 +438,10 @@ impl<'a, 'input> Compiler<'a, 'input> {
     ) -> CompileResult<(usize, Vec<Gc<Function>>, Vec<UpVarDef>)> {
         self.upvars_stack.push(Vec::new());
         let mut vars = HashMap::new();
-        vars.insert(SmartString::from("self"), (false, 0));
+        vars.insert(String::from("self"), (false, 0));
         let mut process_var = |var_sp: Span| {
             let vars_len = vars.len();
-            let var_str = SmartString::from(self.lexer.span_str(var_sp));
+            let var_str = String::from(self.lexer.span_str(var_sp));
             match vars.entry(var_str.clone()) {
                 hash_map::Entry::Occupied(_) => Err(vec![(
                     var_sp,
@@ -542,7 +536,7 @@ impl<'a, 'input> Compiler<'a, 'input> {
             ast::Expr::BinaryMsg { span, lhs, op, rhs } => {
                 let mut stack_size = self.c_expr(vm, lhs)?;
                 stack_size = max(stack_size, 1 + self.c_expr(vm, rhs)?);
-                let send_off = vm.add_send((SmartString::from(self.lexer.span_str(*op)), 1));
+                let send_off = vm.add_send((String::from(self.lexer.span_str(*op)), 1));
                 let instr = match lhs {
                     box ast::Expr::UnaryMsg {
                         receiver: box ast::Expr::VarLookup(span2),
@@ -640,7 +634,7 @@ impl<'a, 'input> Compiler<'a, 'input> {
                 msglist,
             } => {
                 let mut max_stack = self.c_expr(vm, receiver)?;
-                let mut mn = SmartString::new();
+                let mut mn = String::new();
                 for (i, (kw, expr)) in msglist.iter().enumerate() {
                     mn.push_str(self.lexer.span_str(*kw));
                     let expr_stack = self.c_expr(vm, expr)?;
@@ -668,7 +662,7 @@ impl<'a, 'input> Compiler<'a, 'input> {
             } => {
                 let max_stack = self.c_expr(vm, receiver)?;
                 for (i, id) in ids.iter().enumerate() {
-                    let send_off = vm.add_send((SmartString::from(self.lexer.span_str(*id)), 0));
+                    let send_off = vm.add_send((String::from(self.lexer.span_str(*id)), 0));
                     let instr = match receiver {
                         box ast::Expr::VarLookup(span)
                             if i == 0 && self.lexer.span_str(*span) == "super" =>
@@ -697,7 +691,7 @@ impl<'a, 'input> Compiler<'a, 'input> {
                     // "self" as an upvalue.
                     let locals_stack_len = self.locals_stack[1].len();
                     self.locals_stack[1]
-                        .entry(SmartString::from(CLOSURE_RETURN_VAR))
+                        .entry(String::from(CLOSURE_RETURN_VAR))
                         .or_insert((false, locals_stack_len));
                     match self.find_var_name(CLOSURE_RETURN_VAR) {
                         VarLookup::UpVar(upidx) => {
@@ -711,7 +705,7 @@ impl<'a, 'input> Compiler<'a, 'input> {
             }
             ast::Expr::String(span) => {
                 let s_orig = self.lexer.span_str(*span);
-                let mut new_s = SmartString::new();
+                let mut new_s = String::new();
                 // Start by ignoring the beginning quote.
                 let mut i = '\"'.len_utf8();
                 // End by ignoring the beginning quote.
@@ -752,13 +746,13 @@ impl<'a, 'input> Compiler<'a, 'input> {
                 // XXX are there string escaping rules we need to take account of?
                 let s_orig = self.lexer.span_str(*span);
                 // Strip off the beginning/end quotes.
-                let s = SmartString::from(&s_orig[1..s_orig.len() - 1]);
+                let s = String::from(&s_orig[1..s_orig.len() - 1]);
                 let instr = Instr::Symbol(vm.add_symbol(s));
                 vm.instrs_push(instr, *span);
                 Ok(1)
             }
             ast::Expr::Symbol(span) => {
-                let s = SmartString::from(self.lexer.span_str(*span));
+                let s = String::from(self.lexer.span_str(*span));
                 let instr = Instr::Symbol(vm.add_symbol(s));
                 vm.instrs_push(instr, *span);
                 Ok(1)
@@ -814,7 +808,7 @@ impl<'a, 'input> Compiler<'a, 'input> {
                     e.1
                 };
                 self.upvars_stack[depth + 1].push((
-                    SmartString::from(name),
+                    String::from(name),
                     UpVarDef {
                         capture_local: true,
                         upidx,
@@ -828,7 +822,7 @@ impl<'a, 'input> Compiler<'a, 'input> {
                     let mut upidx = i;
                     for j in depth + 1..self.upvars_stack.len() {
                         self.upvars_stack[j].push((
-                            SmartString::from(name),
+                            String::from(name),
                             UpVarDef {
                                 capture_local: false,
                                 upidx,
diff --git a/src/lib/vm/core.rs b/src/lib/vm/core.rs
index 54c532e1..c2c406eb 100644
--- a/src/lib/vm/core.rs
+++ b/src/lib/vm/core.rs
@@ -13,7 +13,7 @@ use std::{
 
 use lrpar::Span;
 use num_bigint::BigInt;
-use smartstring::alias::String as SmartString;
+
 use static_assertions::const_assert;
 use std::gc::Gc;
 
@@ -78,24 +78,24 @@ pub struct VM {
     /// The current known set of globals including those not yet assigned to: in other words, it is
     /// expected that some entries of this `Vec` are illegal (i.e. created by `Val::illegal`).
     globals: Vec<Val>,
-    reverse_globals: HashMap<SmartString, usize>,
+    reverse_globals: HashMap<String, usize>,
     inline_caches: Vec<Option<(Val, Gc<Method>)>>,
     /// `instrs` and `instr_span`s are always the same length: they are separated only because we
     /// rarely access `instr_spans`.
     instrs: Vec<Instr>,
     instr_spans: Vec<Span>,
-    sends: Vec<(Gc<SmartString>, usize)>,
+    sends: Vec<(Gc<String>, usize)>,
     /// reverse_sends is an optimisation allowing us to reuse sends: it maps a send `(String,
     /// usize)` to a `usize` where the latter represents the index of the send in `sends`.
-    reverse_sends: HashMap<(Gc<SmartString>, usize), usize>,
+    reverse_sends: HashMap<(Gc<String>, usize), usize>,
     stack: Gc<SOMStack>,
     arbints: Vec<Val>,
     strings: Vec<Val>,
     /// reverse_strings is an optimisation allowing us to reuse strings: it maps a `String to a
     /// `usize` where the latter represents the index of the string in `strings`.
-    reverse_strings: HashMap<SmartString, usize>,
+    reverse_strings: HashMap<String, usize>,
     symbols: Vec<Val>,
-    reverse_symbols: HashMap<SmartString, usize>,
+    reverse_symbols: HashMap<String, usize>,
     time_at_start: Instant,
     open_upvars: Option<Gc<UpVar>>,
 }
@@ -850,7 +850,7 @@ impl VM {
                             Err(_) => {
                                 return SendReturn::Err(VMError::new(
                                     self,
-                                    VMErrorKind::InvalidInteger(SmartString::from(s)),
+                                    VMErrorKind::InvalidInteger(String::from(s)),
                                 ))
                             }
                         },
@@ -861,7 +861,7 @@ impl VM {
                         Err(_) => {
                             return SendReturn::Err(VMError::new(
                                 self,
-                                VMErrorKind::InvalidDouble(SmartString::from(s)),
+                                VMErrorKind::InvalidDouble(String::from(s)),
                             ))
                         }
                     }
@@ -1061,7 +1061,7 @@ impl VM {
                 let path = PathBuf::from(stry!(path_val.downcast::<String_>(self)).as_str());
                 match read_to_string(path) {
                     Ok(s) => {
-                        let v = String_::new_str(self, SmartString::from(s));
+                        let v = String_::new_str(self, String::from(s));
                         self.stack.push(v);
                     }
                     Err(_) => self.stack.push(self.nil),
@@ -1408,7 +1408,7 @@ impl VM {
 
     /// Add the send `send` to the VM, returning its index. Note that sends are reused, so indexes
     /// are also reused.
-    pub fn add_send(&mut self, send: (SmartString, usize)) -> usize {
+    pub fn add_send(&mut self, send: (String, usize)) -> usize {
         // We want to avoid `clone`ing `send` in the (hopefully common) case of a cache hit, hence
         // this slightly laborious dance and double-lookup.
         let send = (Gc::new(send.0), send.1);
@@ -1432,7 +1432,7 @@ impl VM {
 
     /// Add the string `s` to the VM, returning its index. Note that strings are reused, so indexes
     /// are also reused.
-    pub fn add_string(&mut self, s: SmartString) -> usize {
+    pub fn add_string(&mut self, s: String) -> usize {
         // We want to avoid `clone`ing `s` in the (hopefully common) case of a cache hit, hence
         // this slightly laborious dance and double-lookup.
         if let Some(i) = self.reverse_strings.get(&s) {
@@ -1448,7 +1448,7 @@ impl VM {
 
     /// Add the symbol `s` to the VM, returning its index. Note that symbols are reused, so indexes
     /// are also reused.
-    pub fn add_symbol(&mut self, s: SmartString) -> usize {
+    pub fn add_symbol(&mut self, s: String) -> usize {
         // We want to avoid `clone`ing `s` in the (hopefully common) case of a cache hit, hence
         // this slightly laborious dance and double-lookup.
         if let Some(i) = self.reverse_symbols.get(&s) {
@@ -1469,7 +1469,7 @@ impl VM {
             *i
         } else {
             let len = self.globals.len();
-            self.reverse_globals.insert(SmartString::from(s), len);
+            self.reverse_globals.insert(String::from(s), len);
             self.globals.push(Val::illegal());
             len
         }
@@ -1516,7 +1516,7 @@ impl VM {
             self.globals[*i] = v;
         } else {
             self.reverse_globals
-                .insert(SmartString::from(name), self.globals.len());
+                .insert(String::from(name), self.globals.len());
             self.globals.push(v);
         }
     }
diff --git a/src/lib/vm/error.rs b/src/lib/vm/error.rs
index df78825e..78b26caf 100644
--- a/src/lib/vm/error.rs
+++ b/src/lib/vm/error.rs
@@ -1,7 +1,7 @@
 use std::{fs::read_to_string, io::stderr};
 
 use lrpar::Span;
-use smartstring::alias::String as SmartString;
+
 use std::gc::Gc;
 use termion::{is_tty, style};
 
@@ -163,9 +163,9 @@ pub enum VMErrorKind {
         got_cls: Val,
     },
     /// Tried to convert an invalid string to a Double.
-    InvalidDouble(SmartString),
+    InvalidDouble(String),
     /// Tried to convert an invalid string to an Integer.
-    InvalidInteger(SmartString),
+    InvalidInteger(String),
     /// Tried to access a global before it being initialised.
     InvalidSymbol,
     /// Tried to do a shl or shr with a value below zero.
@@ -182,7 +182,7 @@ pub enum VMErrorKind {
     /// Tried to do a shl that would overflow memory and/or not fit in the required integer size.
     ShiftTooBig,
     /// An unknown global.
-    UnknownGlobal(SmartString),
+    UnknownGlobal(String),
     /// An unknown method.
     UnknownMethod,
     /// Tried calling a method with the wrong number of arguments.
diff --git a/src/lib/vm/objects/block.rs b/src/lib/vm/objects/block.rs
index 96cb356f..bb64dc59 100644
--- a/src/lib/vm/objects/block.rs
+++ b/src/lib/vm/objects/block.rs
@@ -74,10 +74,15 @@ pub struct Block {
     pub method_stack_base: usize,
 }
 
-// By default, `Block` is not `FinalizerSafe` because it has fields to other
-// `Gc`s. These fields would be unsound to access inside a `drop` method, so
-// this explicit impl is needed to tell the compiler we are not doing that.
+// The following impls are needed to allow the GC to finalise `Block`. By
+// default, `Block` is not `FinalizerSafe` because it has fields to other `Gc`s.
+// These fields would be unsound to access inside a `drop` method, so this
+// explicit impl is needed to tell the compiler we are not doing that. The only
+// time a `Block` is shared between threads is inside a finaliser, which is
+// Sync-safe because we guarantee it will not be accessed at the same time as
+// the main-thread.
 unsafe impl FinalizerSafe for Block {}
+unsafe impl Sync for Block {}
 
 impl Obj for Block {
     fn dyn_objtype(self: Gc<Self>) -> ObjType {
diff --git a/src/lib/vm/objects/class.rs b/src/lib/vm/objects/class.rs
index 7944b34f..f44e74f8 100644
--- a/src/lib/vm/objects/class.rs
+++ b/src/lib/vm/objects/class.rs
@@ -8,7 +8,6 @@ use std::{
     str,
 };
 
-use smartstring::alias::String as SmartString;
 use std::gc::{Gc, NonFinalizable};
 
 use crate::vm::{
@@ -26,14 +25,14 @@ pub struct Class {
     /// Offset to this class's instructions in VM::instrs.
     pub instrs_off: usize,
     supercls: Cell<Val>,
-    pub inst_vars_map: NonFinalizable<HashMap<SmartString, usize>>,
+    pub inst_vars_map: NonFinalizable<HashMap<String, usize>>,
     /// A SOM Array of methods (though note that it is *not* guaranteed that these definitely point
     /// to SOM `Method` instances -- anything can be stored in this array!).
     methods: Val,
     /// A map from method names to indexes into the methods SOM Array. Note that indexes are stored
     /// with SOM indexing (starting from 1). We guarantee that the indexes are valid indexes for
     /// the `methods` array.
-    methods_map: NonFinalizable<HashMap<SmartString, usize>>,
+    methods_map: NonFinalizable<HashMap<String, usize>>,
     inst_vars: UnsafeCell<Vec<Val>>,
 }
 
@@ -42,6 +41,7 @@ pub struct Class {
 // thread, it is guaranteed that the finalizer thread will be the only thread
 // accessing its data.
 unsafe impl FinalizerSafe for Class {}
+unsafe impl Sync for Class {}
 
 impl Obj for Class {
     fn dyn_objtype(self: Gc<Self>) -> ObjType {
@@ -93,9 +93,9 @@ impl Class {
         path: PathBuf,
         instrs_off: usize,
         supercls: Val,
-        inst_vars_map: NonFinalizable<HashMap<SmartString, usize>>,
+        inst_vars_map: NonFinalizable<HashMap<String, usize>>,
         methods: Val,
-        methods_map: NonFinalizable<HashMap<SmartString, usize>>,
+        methods_map: NonFinalizable<HashMap<String, usize>>,
     ) -> Val {
         #[cfg(debug_assertions)]
         {
diff --git a/src/lib/vm/objects/double.rs b/src/lib/vm/objects/double.rs
index 75b24d0d..0ff06ff9 100644
--- a/src/lib/vm/objects/double.rs
+++ b/src/lib/vm/objects/double.rs
@@ -4,7 +4,7 @@ use std::{collections::hash_map::DefaultHasher, hash::Hasher};
 
 use num_bigint::BigInt;
 use num_traits::{FromPrimitive, ToPrimitive, Zero};
-use smartstring::alias::String as SmartString;
+
 use std::gc::Gc;
 
 use crate::vm::{
@@ -33,10 +33,7 @@ impl Obj for Double {
 
     fn to_strval(self: Gc<Self>, vm: &mut VM) -> Result<Val, Box<VMError>> {
         let mut buf = ryu::Buffer::new();
-        Ok(String_::new_str(
-            vm,
-            SmartString::from(buf.format(self.val)),
-        ))
+        Ok(String_::new_str(vm, String::from(buf.format(self.val))))
     }
 
     fn hashcode(self: Gc<Self>) -> u64 {
diff --git a/src/lib/vm/objects/method.rs b/src/lib/vm/objects/method.rs
index f5cf7b3d..abdf4ebe 100644
--- a/src/lib/vm/objects/method.rs
+++ b/src/lib/vm/objects/method.rs
@@ -22,6 +22,7 @@ pub struct Method {
 // method. This explicit impl is needed to tell the compiler we are not doing
 // that.
 unsafe impl FinalizerSafe for Method {}
+unsafe impl Sync for Method {}
 
 impl Obj for Method {
     fn dyn_objtype(self: Gc<Self>) -> ObjType {
diff --git a/src/lib/vm/objects/mod.rs b/src/lib/vm/objects/mod.rs
index c1e5033d..0015c9b4 100644
--- a/src/lib/vm/objects/mod.rs
+++ b/src/lib/vm/objects/mod.rs
@@ -40,6 +40,7 @@ pub use string_::String_;
 
 use natrob::narrowable_alloy;
 use std::gc::Gc;
+use std::gc::ReferenceFree;
 
 use crate::vm::{
     core::VM,
@@ -80,7 +81,7 @@ impl ObjType {
 /// The main SOM Object trait. Notice that code should almost never call these functions directly:
 /// you should instead call the equivalent function in the `Val` struct.
 #[narrowable_alloy(ThinObj)]
-pub trait Obj: std::fmt::Debug + FinalizerSafe {
+pub trait Obj: std::fmt::Debug + Send + Sync + FinalizerSafe + ReferenceFree {
     /// What `ObjType` does this `Val` represent?
     fn dyn_objtype(self: Gc<Self>) -> ObjType;
 
diff --git a/src/lib/vm/objects/string_.rs b/src/lib/vm/objects/string_.rs
index 4cd1d1a4..a2d58f24 100644
--- a/src/lib/vm/objects/string_.rs
+++ b/src/lib/vm/objects/string_.rs
@@ -7,7 +7,6 @@ use std::{
     str,
 };
 
-use smartstring::alias::String as SmartString;
 use std::gc::Gc;
 
 use crate::vm::{
@@ -26,7 +25,7 @@ pub struct String_ {
     /// that if anyone ever manages to make a string of usize::MAX characters, we won't cache its
     /// length correctly, but will recalculate it each time.
     chars_len: Cell<usize>,
-    s: SmartString,
+    s: String,
 }
 
 // This is safe because there is no non-GC'd shared ownership inside `String_`.
@@ -34,6 +33,7 @@ pub struct String_ {
 // thread, it is guaranteed that the finalizer thread will be the only thread
 // accessing its data.
 unsafe impl FinalizerSafe for String_ {}
+unsafe impl Sync for String_ {}
 
 impl Obj for String_ {
     fn dyn_objtype(self: Gc<Self>) -> ObjType {
@@ -98,13 +98,13 @@ impl StaticObjType for String_ {
 }
 
 impl String_ {
-    pub fn new_str(vm: &mut VM, s: SmartString) -> Val {
+    pub fn new_str(vm: &mut VM, s: String) -> Val {
         String_::new_str_chars_len(vm, s, usize::MAX)
     }
 
     /// Create a new `String_` whose number of Unicode characters is already known. Note that it is
     /// safe to pass `usize::MAX` for `chars_len`.
-    fn new_str_chars_len(vm: &mut VM, s: SmartString, chars_len: usize) -> Val {
+    fn new_str_chars_len(vm: &mut VM, s: String, chars_len: usize) -> Val {
         Val::from_obj(String_ {
             cls: Cell::new(vm.str_cls),
             chars_len: Cell::new(chars_len),
@@ -112,7 +112,7 @@ impl String_ {
         })
     }
 
-    pub fn new_sym(vm: &mut VM, s: SmartString) -> Val {
+    pub fn new_sym(vm: &mut VM, s: String) -> Val {
         Val::from_obj(String_ {
             cls: Cell::new(vm.sym_cls),
             chars_len: Cell::new(usize::MAX),
@@ -169,7 +169,7 @@ impl String_ {
             todo!();
         }
         if end < start {
-            return Ok(String_::new_str(vm, SmartString::new()));
+            return Ok(String_::new_str(vm, String::new()));
         }
         if start > self.s.len() || end > self.s.len() {
             todo!();
diff --git a/src/lib/vm/val.rs b/src/lib/vm/val.rs
index 9db33f99..f933456f 100644
--- a/src/lib/vm/val.rs
+++ b/src/lib/vm/val.rs
@@ -9,8 +9,6 @@ use num_enum::{IntoPrimitive, UnsafeFromPrimitive};
 use num_traits::{FromPrimitive, ToPrimitive};
 use std::gc::Gc;
 
-use std::gc::NoTrace;
-
 use super::{
     core::VM,
     error::{VMError, VMErrorKind},
@@ -62,8 +60,6 @@ pub struct Val {
     pub val: usize,
 }
 
-impl !NoTrace for Val {}
-
 impl Val {
     /// Create a new `Val` from an object that should be allocated on the heap.
     pub fn from_obj<T: Obj + 'static>(obj: T) -> Val {
@@ -666,7 +662,6 @@ mod tests {
     };
 
     use serial_test::serial;
-    use smartstring::alias::String as SmartString;
 
     #[test]
     #[serial]
@@ -737,7 +732,7 @@ mod tests {
         assert_eq!(v.as_usize(&mut vm).unwrap(), 1 << (BITSIZE - 2));
         assert_eq!(v.as_isize(&mut vm).unwrap(), 1 << (BITSIZE - 2));
 
-        let v = String_::new_str(&mut vm, SmartString::new());
+        let v = String_::new_str(&mut vm, String::new());
         assert!(v.as_usize(&mut vm).is_err());
     }
 
@@ -747,7 +742,7 @@ mod tests {
         let mut vm = VM::new_no_bootstrap();
 
         let v = {
-            let v = String_::new_str(&mut vm, SmartString::from("s"));
+            let v = String_::new_str(&mut vm, String::from("s"));
             let v_tobj = v.tobj(&mut vm).unwrap();
             let v_str: Gc<String_> = v_tobj.downcast().unwrap();
             let v_recovered = Val::recover(v_str);
@@ -763,7 +758,7 @@ mod tests {
     #[serial]
     fn test_cast() {
         let mut vm = VM::new_no_bootstrap();
-        let v = String_::new_str(&mut vm, SmartString::from("s"));
+        let v = String_::new_str(&mut vm, String::from("s"));
         assert!(v.downcast::<String_>(&mut vm).is_ok());
         assert_eq!(
             v.downcast::<Class>(&mut vm).unwrap_err().kind,
@@ -778,7 +773,7 @@ mod tests {
     #[serial]
     fn test_downcast() {
         let mut vm = VM::new_no_bootstrap();
-        let v = String_::new_str(&mut vm, SmartString::from("s"));
+        let v = String_::new_str(&mut vm, String::from("s"));
         assert!(v.downcast::<String_>(&mut vm).is_ok());
         assert!(v.downcast::<Class>(&mut vm).is_err());
         assert!(v.try_downcast::<String_>(&mut vm).is_some());
diff --git a/src/main.rs b/src/main.rs
index 1987cf03..ca8345af 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -12,7 +12,6 @@ use std::{
 };
 
 use getopts::Options;
-use smartstring::alias::String as SmartString;
 
 use yksom::vm::{
     objects::{NormalArray, String_},
@@ -99,14 +98,14 @@ fn main() {
     };
     let mut src_fname = PathBuf::from(src_fname);
     src_fname.set_extension("");
-    let src_fname_val = String_::new_str(&mut vm, SmartString::from(src_fname.to_str().unwrap()));
+    let src_fname_val = String_::new_str(&mut vm, String::from(src_fname.to_str().unwrap()));
     let mut args_vec = vec![src_fname_val];
     args_vec.extend(
         matches
             .free
             .iter()
             .skip(1)
-            .map(|x| String_::new_str(&mut vm, SmartString::from(x))),
+            .map(|x| String_::new_str(&mut vm, String::from(x))),
     );
     let args = NormalArray::from_vec(args_vec);
     match vm.top_level_send(system, "initialize:", vec![args]) {