diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 82156fb6b0..59c82b4983 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -73,6 +73,7 @@ jobs:
       - name: Check parser error messages exhaustiveness
         run: |
           npm run compiler parser:check-errors
+          npm run compiler graindoc-parser:check-errors
 
       # Formatting lint last because building is more important
       - name: Run formatting lint
diff --git a/compiler/esy.json b/compiler/esy.json
index b6983c1d30..5307e00283 100644
--- a/compiler/esy.json
+++ b/compiler/esy.json
@@ -38,7 +38,7 @@
     "@opam/dune-configurator": ">= 3.6.1 < 4.0.0",
     "@opam/fp": "0.0.1",
     "@opam/fs": "0.0.2",
-    "@opam/menhir": "20211125",
+    "@opam/menhir": "20220210",
     "@opam/ocamlgraph": ">= 2.0.0 < 3.0.0",
     "@opam/ppx_deriving": ">= 5.2.1 < 6.0.0",
     "@opam/ppx_deriving_cmdliner": ">= 0.6.1",
diff --git a/compiler/esy.lock/index.json b/compiler/esy.lock/index.json
index d4a1ec149b..1bfe393942 100644
--- a/compiler/esy.lock/index.json
+++ b/compiler/esy.lock/index.json
@@ -1,5 +1,5 @@
 {
-  "checksum": "c0fd160e669e4135a3c194cb5123a95e",
+  "checksum": "c922120cb5fa1586903a0da6b7150e13",
   "root": "@grain/compiler@link-dev:./esy.json",
   "node": {
     "yarn-pkg-config@github:esy-ocaml/yarn-pkg-config#db3a0b63883606dd57c54a7158d560d6cba8cd79@d41d8cd9": {
@@ -220,7 +220,7 @@
       "overrides": [],
       "dependencies": [
         "ocaml@github:phated/ocaml:package.json#a25997805f1ce225f23c0321e827c0d503896017@d41d8cd9",
-        "@opam/topkg@opam:1.0.6@da3f4ab1",
+        "@opam/topkg@opam:1.0.7@7ee47d76",
         "@opam/ocamlfind@opam:1.9.5@c23112ba",
         "@opam/ocamlbuild@opam:0.14.2@c6163b28",
         "@opam/cmdliner@opam:1.1.1@03763729",
@@ -250,7 +250,7 @@
       "dependencies": [
         "ocaml@github:phated/ocaml:package.json#a25997805f1ce225f23c0321e827c0d503896017@d41d8cd9",
         "@opam/uutf@opam:1.0.3@47c95a18", "@opam/uucp@opam:15.0.0@55460339",
-        "@opam/topkg@opam:1.0.6@da3f4ab1",
+        "@opam/topkg@opam:1.0.7@7ee47d76",
         "@opam/ocamlfind@opam:1.9.5@c23112ba",
         "@opam/ocamlbuild@opam:0.14.2@c6163b28",
         "@opam/cmdliner@opam:1.1.1@03763729",
@@ -280,7 +280,7 @@
       "overrides": [],
       "dependencies": [
         "ocaml@github:phated/ocaml:package.json#a25997805f1ce225f23c0321e827c0d503896017@d41d8cd9",
-        "@opam/uutf@opam:1.0.3@47c95a18", "@opam/topkg@opam:1.0.6@da3f4ab1",
+        "@opam/uutf@opam:1.0.3@47c95a18", "@opam/topkg@opam:1.0.7@7ee47d76",
         "@opam/ocamlfind@opam:1.9.5@c23112ba",
         "@opam/ocamlbuild@opam:0.14.2@c6163b28",
         "@opam/cmdliner@opam:1.1.1@03763729",
@@ -290,20 +290,20 @@
         "ocaml@github:phated/ocaml:package.json#a25997805f1ce225f23c0321e827c0d503896017@d41d8cd9"
       ]
     },
-    "@opam/utop@opam:2.10.0@9af1bb18": {
-      "id": "@opam/utop@opam:2.10.0@9af1bb18",
+    "@opam/utop@opam:2.11.0@bd245e47": {
+      "id": "@opam/utop@opam:2.11.0@bd245e47",
       "name": "@opam/utop",
-      "version": "opam:2.10.0",
+      "version": "opam:2.11.0",
       "source": {
         "type": "install",
         "source": [
-          "archive:https://opam.ocaml.org/cache/sha256/47/475d16a2f9ea61c602ac32673ee210c76cc768f7214987d70c069532c2782d00#sha256:475d16a2f9ea61c602ac32673ee210c76cc768f7214987d70c069532c2782d00",
-          "archive:https://github.com/ocaml-community/utop/releases/download/2.10.0/utop-2.10.0.tbz#sha256:475d16a2f9ea61c602ac32673ee210c76cc768f7214987d70c069532c2782d00"
+          "archive:https://opam.ocaml.org/cache/sha256/69/6937c6c672913ac3b875341ac4a205c7561d01cd8ac8f47cfb35d3bc0e762170#sha256:6937c6c672913ac3b875341ac4a205c7561d01cd8ac8f47cfb35d3bc0e762170",
+          "archive:https://github.com/ocaml-community/utop/releases/download/2.11.0/utop-2.11.0.tbz#sha256:6937c6c672913ac3b875341ac4a205c7561d01cd8ac8f47cfb35d3bc0e762170"
         ],
         "opam": {
           "name": "utop",
-          "version": "2.10.0",
-          "path": "esy.lock/opam/utop.2.10.0"
+          "version": "2.11.0",
+          "path": "esy.lock/opam/utop.2.11.0"
         }
       },
       "overrides": [],
@@ -442,20 +442,20 @@
         "@opam/dune@opam:3.6.1@662f326b"
       ]
     },
-    "@opam/topkg@opam:1.0.6@da3f4ab1": {
-      "id": "@opam/topkg@opam:1.0.6@da3f4ab1",
+    "@opam/topkg@opam:1.0.7@7ee47d76": {
+      "id": "@opam/topkg@opam:1.0.7@7ee47d76",
       "name": "@opam/topkg",
-      "version": "opam:1.0.6",
+      "version": "opam:1.0.7",
       "source": {
         "type": "install",
         "source": [
-          "archive:https://opam.ocaml.org/cache/sha512/8e/8e34391e2f499cec332b79454a4edb36a35db6fe22437f017fd5c80ae065160dc967ac02d894a94d08d62dd476521e63733f4cadc3b9b6b314b6aa5b2b4ede78#sha512:8e34391e2f499cec332b79454a4edb36a35db6fe22437f017fd5c80ae065160dc967ac02d894a94d08d62dd476521e63733f4cadc3b9b6b314b6aa5b2b4ede78",
-          "archive:https://erratique.ch/software/topkg/releases/topkg-1.0.6.tbz#sha512:8e34391e2f499cec332b79454a4edb36a35db6fe22437f017fd5c80ae065160dc967ac02d894a94d08d62dd476521e63733f4cadc3b9b6b314b6aa5b2b4ede78"
+          "archive:https://opam.ocaml.org/cache/sha512/09/09e59f1759bf4db8471f02d0aefd8db602b44932a291c05c312b1423796e7a15d1598d3c62a0cec7f083eff8e410fac09363533dc4bd2120914bb9664efea535#sha512:09e59f1759bf4db8471f02d0aefd8db602b44932a291c05c312b1423796e7a15d1598d3c62a0cec7f083eff8e410fac09363533dc4bd2120914bb9664efea535",
+          "archive:https://erratique.ch/software/topkg/releases/topkg-1.0.7.tbz#sha512:09e59f1759bf4db8471f02d0aefd8db602b44932a291c05c312b1423796e7a15d1598d3c62a0cec7f083eff8e410fac09363533dc4bd2120914bb9664efea535"
         ],
         "opam": {
           "name": "topkg",
-          "version": "1.0.6",
-          "path": "esy.lock/opam/topkg.1.0.6"
+          "version": "1.0.7",
+          "path": "esy.lock/opam/topkg.1.0.7"
         }
       },
       "overrides": [],
@@ -627,13 +627,13 @@
       "dependencies": [
         "ocaml@github:phated/ocaml:package.json#a25997805f1ce225f23c0321e827c0d503896017@d41d8cd9",
         "@opam/sexplib0@opam:v0.15.1@51111c0c",
-        "@opam/parsexp@opam:v0.15.0@742345c3", "@opam/num@opam:1.4@54b259a0",
+        "@opam/parsexp@opam:v0.15.0@742345c3", "@opam/num@opam:1.4@16d26a67",
         "@opam/dune@opam:3.6.1@662f326b", "@esy-ocaml/substs@0.0.1@d41d8cd9"
       ],
       "devDependencies": [
         "ocaml@github:phated/ocaml:package.json#a25997805f1ce225f23c0321e827c0d503896017@d41d8cd9",
         "@opam/sexplib0@opam:v0.15.1@51111c0c",
-        "@opam/parsexp@opam:v0.15.0@742345c3", "@opam/num@opam:1.4@54b259a0",
+        "@opam/parsexp@opam:v0.15.0@742345c3", "@opam/num@opam:1.4@16d26a67",
         "@opam/dune@opam:3.6.1@662f326b"
       ]
     },
@@ -738,7 +738,7 @@
         "@opam/ppx_derivers@opam:1.2.1@e2cbad12",
         "@opam/ocamlfind@opam:1.9.5@c23112ba",
         "@opam/merlin-extend@opam:0.6.1@7d979feb",
-        "@opam/menhir@opam:20211125@5ae9a0c2",
+        "@opam/menhir@opam:20220210@ff5ea9a7",
         "@opam/fix@opam:20220121@17b9a1a4", "@opam/dune@opam:3.6.1@662f326b",
         "@esy-ocaml/substs@0.0.1@d41d8cd9"
       ],
@@ -747,7 +747,7 @@
         "@opam/result@opam:1.5@1c6a6533",
         "@opam/ppx_derivers@opam:1.2.1@e2cbad12",
         "@opam/merlin-extend@opam:0.6.1@7d979feb",
-        "@opam/menhir@opam:20211125@5ae9a0c2",
+        "@opam/menhir@opam:20220210@ff5ea9a7",
         "@opam/fix@opam:20220121@17b9a1a4", "@opam/dune@opam:3.6.1@662f326b"
       ]
     },
@@ -770,7 +770,7 @@
       "overrides": [],
       "dependencies": [
         "ocaml@github:phated/ocaml:package.json#a25997805f1ce225f23c0321e827c0d503896017@d41d8cd9",
-        "@opam/topkg@opam:1.0.6@da3f4ab1",
+        "@opam/topkg@opam:1.0.7@7ee47d76",
         "@opam/ocamlfind@opam:1.9.5@c23112ba",
         "@opam/ocamlbuild@opam:0.14.2@c6163b28",
         "@esy-ocaml/substs@0.0.1@d41d8cd9"
@@ -919,14 +919,14 @@
         "ocaml@github:phated/ocaml:package.json#a25997805f1ce225f23c0321e827c0d503896017@d41d8cd9",
         "@opam/yojson@opam:2.0.2@eb65f292", "@opam/result@opam:1.5@1c6a6533",
         "@opam/ppxlib@opam:0.28.0@8c51d241",
-        "@opam/ppx_deriving@opam:5.2.1@089e5dd3",
+        "@opam/ppx_deriving@opam:5.2.1@2315fdd0",
         "@opam/dune@opam:3.6.1@662f326b", "@esy-ocaml/substs@0.0.1@d41d8cd9"
       ],
       "devDependencies": [
         "ocaml@github:phated/ocaml:package.json#a25997805f1ce225f23c0321e827c0d503896017@d41d8cd9",
         "@opam/yojson@opam:2.0.2@eb65f292", "@opam/result@opam:1.5@1c6a6533",
         "@opam/ppxlib@opam:0.28.0@8c51d241",
-        "@opam/ppx_deriving@opam:5.2.1@089e5dd3",
+        "@opam/ppx_deriving@opam:5.2.1@2315fdd0",
         "@opam/dune@opam:3.6.1@662f326b"
       ]
     },
@@ -947,7 +947,7 @@
         "ocaml@github:phated/ocaml:package.json#a25997805f1ce225f23c0321e827c0d503896017@d41d8cd9",
         "@opam/result@opam:1.5@1c6a6533",
         "@opam/ppxlib@opam:0.28.0@8c51d241",
-        "@opam/ppx_deriving@opam:5.2.1@089e5dd3",
+        "@opam/ppx_deriving@opam:5.2.1@2315fdd0",
         "@opam/dune@opam:3.6.1@662f326b",
         "@opam/cmdliner@opam:1.1.1@03763729",
         "@esy-ocaml/substs@0.0.1@d41d8cd9"
@@ -956,13 +956,13 @@
         "ocaml@github:phated/ocaml:package.json#a25997805f1ce225f23c0321e827c0d503896017@d41d8cd9",
         "@opam/result@opam:1.5@1c6a6533",
         "@opam/ppxlib@opam:0.28.0@8c51d241",
-        "@opam/ppx_deriving@opam:5.2.1@089e5dd3",
+        "@opam/ppx_deriving@opam:5.2.1@2315fdd0",
         "@opam/dune@opam:3.6.1@662f326b",
         "@opam/cmdliner@opam:1.1.1@03763729"
       ]
     },
-    "@opam/ppx_deriving@opam:5.2.1@089e5dd3": {
-      "id": "@opam/ppx_deriving@opam:5.2.1@089e5dd3",
+    "@opam/ppx_deriving@opam:5.2.1@2315fdd0": {
+      "id": "@opam/ppx_deriving@opam:5.2.1@2315fdd0",
       "name": "@opam/ppx_deriving",
       "version": "opam:5.2.1",
       "source": {
@@ -1407,8 +1407,8 @@
         "@opam/dune@opam:3.6.1@662f326b"
       ]
     },
-    "@opam/num@opam:1.4@54b259a0": {
-      "id": "@opam/num@opam:1.4@54b259a0",
+    "@opam/num@opam:1.4@16d26a67": {
+      "id": "@opam/num@opam:1.4@16d26a67",
       "name": "@opam/num",
       "version": "opam:1.4",
       "source": {
@@ -1521,20 +1521,20 @@
         "@opam/dune@opam:3.6.1@662f326b"
       ]
     },
-    "@opam/menhirSdk@opam:20211125@60ac0b7e": {
-      "id": "@opam/menhirSdk@opam:20211125@60ac0b7e",
+    "@opam/menhirSdk@opam:20220210@fe146ed3": {
+      "id": "@opam/menhirSdk@opam:20220210@fe146ed3",
       "name": "@opam/menhirSdk",
-      "version": "opam:20211125",
+      "version": "opam:20220210",
       "source": {
         "type": "install",
         "source": [
-          "archive:https://opam.ocaml.org/cache/md5/27/27ddfc9be183d6ae8f5440d807c68e38#md5:27ddfc9be183d6ae8f5440d807c68e38",
-          "archive:https://gitlab.inria.fr/fpottier/menhir/-/archive/20211125/archive.tar.gz#md5:27ddfc9be183d6ae8f5440d807c68e38"
+          "archive:https://opam.ocaml.org/cache/md5/e3/e3cef220f676c4b1c16cbccb174cefe3#md5:e3cef220f676c4b1c16cbccb174cefe3",
+          "archive:https://gitlab.inria.fr/fpottier/menhir/-/archive/20220210/archive.tar.gz#md5:e3cef220f676c4b1c16cbccb174cefe3"
         ],
         "opam": {
           "name": "menhirSdk",
-          "version": "20211125",
-          "path": "esy.lock/opam/menhirSdk.20211125"
+          "version": "20220210",
+          "path": "esy.lock/opam/menhirSdk.20220210"
         }
       },
       "overrides": [],
@@ -1547,20 +1547,20 @@
         "@opam/dune@opam:3.6.1@662f326b"
       ]
     },
-    "@opam/menhirLib@opam:20211125@cd0b955b": {
-      "id": "@opam/menhirLib@opam:20211125@cd0b955b",
+    "@opam/menhirLib@opam:20220210@9afeb270": {
+      "id": "@opam/menhirLib@opam:20220210@9afeb270",
       "name": "@opam/menhirLib",
-      "version": "opam:20211125",
+      "version": "opam:20220210",
       "source": {
         "type": "install",
         "source": [
-          "archive:https://opam.ocaml.org/cache/md5/27/27ddfc9be183d6ae8f5440d807c68e38#md5:27ddfc9be183d6ae8f5440d807c68e38",
-          "archive:https://gitlab.inria.fr/fpottier/menhir/-/archive/20211125/archive.tar.gz#md5:27ddfc9be183d6ae8f5440d807c68e38"
+          "archive:https://opam.ocaml.org/cache/md5/e3/e3cef220f676c4b1c16cbccb174cefe3#md5:e3cef220f676c4b1c16cbccb174cefe3",
+          "archive:https://gitlab.inria.fr/fpottier/menhir/-/archive/20220210/archive.tar.gz#md5:e3cef220f676c4b1c16cbccb174cefe3"
         ],
         "opam": {
           "name": "menhirLib",
-          "version": "20211125",
-          "path": "esy.lock/opam/menhirLib.20211125"
+          "version": "20220210",
+          "path": "esy.lock/opam/menhirLib.20220210"
         }
       },
       "overrides": [],
@@ -1573,33 +1573,33 @@
         "@opam/dune@opam:3.6.1@662f326b"
       ]
     },
-    "@opam/menhir@opam:20211125@5ae9a0c2": {
-      "id": "@opam/menhir@opam:20211125@5ae9a0c2",
+    "@opam/menhir@opam:20220210@ff5ea9a7": {
+      "id": "@opam/menhir@opam:20220210@ff5ea9a7",
       "name": "@opam/menhir",
-      "version": "opam:20211125",
+      "version": "opam:20220210",
       "source": {
         "type": "install",
         "source": [
-          "archive:https://opam.ocaml.org/cache/md5/27/27ddfc9be183d6ae8f5440d807c68e38#md5:27ddfc9be183d6ae8f5440d807c68e38",
-          "archive:https://gitlab.inria.fr/fpottier/menhir/-/archive/20211125/archive.tar.gz#md5:27ddfc9be183d6ae8f5440d807c68e38"
+          "archive:https://opam.ocaml.org/cache/md5/e3/e3cef220f676c4b1c16cbccb174cefe3#md5:e3cef220f676c4b1c16cbccb174cefe3",
+          "archive:https://gitlab.inria.fr/fpottier/menhir/-/archive/20220210/archive.tar.gz#md5:e3cef220f676c4b1c16cbccb174cefe3"
         ],
         "opam": {
           "name": "menhir",
-          "version": "20211125",
-          "path": "esy.lock/opam/menhir.20211125"
+          "version": "20220210",
+          "path": "esy.lock/opam/menhir.20220210"
         }
       },
       "overrides": [],
       "dependencies": [
         "ocaml@github:phated/ocaml:package.json#a25997805f1ce225f23c0321e827c0d503896017@d41d8cd9",
-        "@opam/menhirSdk@opam:20211125@60ac0b7e",
-        "@opam/menhirLib@opam:20211125@cd0b955b",
+        "@opam/menhirSdk@opam:20220210@fe146ed3",
+        "@opam/menhirLib@opam:20220210@9afeb270",
         "@opam/dune@opam:3.6.1@662f326b", "@esy-ocaml/substs@0.0.1@d41d8cd9"
       ],
       "devDependencies": [
         "ocaml@github:phated/ocaml:package.json#a25997805f1ce225f23c0321e827c0d503896017@d41d8cd9",
-        "@opam/menhirSdk@opam:20211125@60ac0b7e",
-        "@opam/menhirLib@opam:20211125@cd0b955b",
+        "@opam/menhirSdk@opam:20220210@fe146ed3",
+        "@opam/menhirLib@opam:20220210@9afeb270",
         "@opam/dune@opam:3.6.1@662f326b"
       ]
     },
@@ -1684,7 +1684,7 @@
       "overrides": [],
       "dependencies": [
         "ocaml@github:phated/ocaml:package.json#a25997805f1ce225f23c0321e827c0d503896017@d41d8cd9",
-        "@opam/topkg@opam:1.0.6@da3f4ab1",
+        "@opam/topkg@opam:1.0.7@7ee47d76",
         "@opam/ocamlfind@opam:1.9.5@c23112ba",
         "@opam/ocamlbuild@opam:0.14.2@c6163b28",
         "@opam/lwt@opam:5.6.1@2a9902ab",
@@ -1730,8 +1730,8 @@
         "@opam/dune@opam:3.6.1@662f326b"
       ]
     },
-    "@opam/js_of_ocaml-compiler@opam:4.0.0@e10fcdb0": {
-      "id": "@opam/js_of_ocaml-compiler@opam:4.0.0@e10fcdb0",
+    "@opam/js_of_ocaml-compiler@opam:4.0.0@5d988f22": {
+      "id": "@opam/js_of_ocaml-compiler@opam:4.0.0@5d988f22",
       "name": "@opam/js_of_ocaml-compiler",
       "version": "opam:4.0.0",
       "source": {
@@ -1757,9 +1757,9 @@
         "@opam/yojson@opam:2.0.2@eb65f292",
         "@opam/ppxlib@opam:0.28.0@8c51d241",
         "@opam/ocamlfind@opam:1.9.5@c23112ba",
-        "@opam/menhirSdk@opam:20211125@60ac0b7e",
-        "@opam/menhirLib@opam:20211125@cd0b955b",
-        "@opam/menhir@opam:20211125@5ae9a0c2",
+        "@opam/menhirSdk@opam:20220210@fe146ed3",
+        "@opam/menhirLib@opam:20220210@9afeb270",
+        "@opam/menhir@opam:20220210@ff5ea9a7",
         "@opam/dune@opam:3.6.1@662f326b",
         "@opam/cmdliner@opam:1.1.1@03763729",
         "@esy-ocaml/substs@0.0.1@d41d8cd9"
@@ -1768,9 +1768,9 @@
         "ocaml@github:phated/ocaml:package.json#a25997805f1ce225f23c0321e827c0d503896017@d41d8cd9",
         "@opam/yojson@opam:2.0.2@eb65f292",
         "@opam/ppxlib@opam:0.28.0@8c51d241",
-        "@opam/menhirSdk@opam:20211125@60ac0b7e",
-        "@opam/menhirLib@opam:20211125@cd0b955b",
-        "@opam/menhir@opam:20211125@5ae9a0c2",
+        "@opam/menhirSdk@opam:20220210@fe146ed3",
+        "@opam/menhirLib@opam:20220210@9afeb270",
+        "@opam/menhir@opam:20220210@ff5ea9a7",
         "@opam/dune@opam:3.6.1@662f326b",
         "@opam/cmdliner@opam:1.1.1@03763729"
       ]
@@ -2400,9 +2400,9 @@
         "@opam/ppx_sexp_conv@opam:v0.15.1@0f138aac",
         "@opam/ppx_deriving_yojson@opam:3.7.0@167442d6",
         "@opam/ppx_deriving_cmdliner@github:hammerlab/ppx_deriving_cmdliner:ppx_deriving_cmdliner.opam#1f086651fe7f8dd98e371b09c6fcc4dbc6db1c7c@d41d8cd9",
-        "@opam/ppx_deriving@opam:5.2.1@089e5dd3",
+        "@opam/ppx_deriving@opam:5.2.1@2315fdd0",
         "@opam/ocamlgraph@opam:2.0.0@929b9eba",
-        "@opam/menhir@opam:20211125@5ae9a0c2",
+        "@opam/menhir@opam:20220210@ff5ea9a7",
         "@opam/fs@github:reasonml/reason-native:fs.opam#0ed854f986256e52e59aeecfa90e9af60f105b15@d41d8cd9",
         "@opam/fp@github:reasonml/reason-native:fp.opam#0ed854f986256e52e59aeecfa90e9af60f105b15@d41d8cd9",
         "@opam/dune-configurator@opam:3.6.1@966be260",
@@ -2414,7 +2414,7 @@
       "devDependencies": [
         "@reason-native/rely@github:reasonml/reason-native:rely.json#0ed854f986256e52e59aeecfa90e9af60f105b15@d41d8cd9",
         "@opam/ocaml-lsp-server@opam:1.14.1@ac41cc96",
-        "@opam/js_of_ocaml-compiler@opam:4.0.0@e10fcdb0"
+        "@opam/js_of_ocaml-compiler@opam:4.0.0@5d988f22"
       ],
       "installConfig": { "pnp": false }
     },
@@ -2467,11 +2467,11 @@
       "overrides": [],
       "dependencies": [
         "ocaml@github:phated/ocaml:package.json#a25997805f1ce225f23c0321e827c0d503896017@d41d8cd9",
-        "@opam/utop@opam:2.10.0@9af1bb18", "@opam/result@opam:1.5@1c6a6533",
+        "@opam/utop@opam:2.11.0@bd245e47", "@opam/result@opam:1.5@1c6a6533",
         "@opam/ppx_derivers@opam:1.2.1@e2cbad12",
         "@opam/ocamlfind@opam:1.9.5@c23112ba",
         "@opam/merlin-extend@opam:0.6.1@7d979feb",
-        "@opam/menhir@opam:20211125@5ae9a0c2",
+        "@opam/menhir@opam:20220210@ff5ea9a7",
         "@opam/fix@opam:20220121@17b9a1a4", "@opam/dune@opam:3.6.1@662f326b"
       ],
       "devDependencies": [
diff --git a/compiler/esy.lock/opam/js_of_ocaml-compiler.4.0.0/opam b/compiler/esy.lock/opam/js_of_ocaml-compiler.4.0.0/opam
index 47bdee230b..e880218768 100644
--- a/compiler/esy.lock/opam/js_of_ocaml-compiler.4.0.0/opam
+++ b/compiler/esy.lock/opam/js_of_ocaml-compiler.4.0.0/opam
@@ -28,6 +28,7 @@ conflicts: [
   "ocamlfind" {< "1.5.1"}
   "js_of_ocaml" {< "3.0"}
   "base-domains"
+  "ocaml-option-bytecode-only"
 ]
 dev-repo: "git+https://github.com/ocsigen/js_of_ocaml.git"
 build: [
diff --git a/compiler/esy.lock/opam/menhir.20211125/opam b/compiler/esy.lock/opam/menhir.20220210/opam
similarity index 69%
rename from compiler/esy.lock/opam/menhir.20211125/opam
rename to compiler/esy.lock/opam/menhir.20220210/opam
index fb1eeb040f..498658b42c 100644
--- a/compiler/esy.lock/opam/menhir.20211125/opam
+++ b/compiler/esy.lock/opam/menhir.20220210/opam
@@ -1,3 +1,4 @@
+
 opam-version: "2.0"
 maintainer: "francois.pottier@inria.fr"
 authors: [
@@ -12,7 +13,7 @@ build: [
   ["dune" "build" "-p" name "-j" jobs]
 ]
 depends: [
-  "ocaml" {>= "4.11.0" & < "5.0"}
+  "ocaml" {>= "4.03.0"}
   "dune" {>= "2.8.0"}
   "menhirLib" {= version}
   "menhirSdk" {= version}
@@ -20,9 +21,9 @@ depends: [
 synopsis: "An LR(1) parser generator"
 url {
   src:
-    "https://gitlab.inria.fr/fpottier/menhir/-/archive/20211125/archive.tar.gz"
+    "https://gitlab.inria.fr/fpottier/menhir/-/archive/20220210/archive.tar.gz"
   checksum: [
-    "md5=27ddfc9be183d6ae8f5440d807c68e38"
-    "sha512=6f09d3008414b652aeee1387c712420635debb1e32539b17a7865805a7d4cf6c8d7dab8d5c6d4c583145f3f2fab07524ae64a832683ad64e832b80557d7526f9"
+    "md5=e3cef220f676c4b1c16cbccb174cefe3"
+    "sha512=3063fec1d8b9fe092c8461b0689d426c7fe381a2bf3fd258dc42ceecca1719d32efbb8a18d94ada5555c38175ea352da3adbb239fdbcbcf52c3a5c85a4d9586f"
   ]
 }
diff --git a/compiler/esy.lock/opam/menhirLib.20211125/opam b/compiler/esy.lock/opam/menhirLib.20220210/opam
similarity index 73%
rename from compiler/esy.lock/opam/menhirLib.20211125/opam
rename to compiler/esy.lock/opam/menhirLib.20220210/opam
index 1029e852ff..d2097ae4f3 100644
--- a/compiler/esy.lock/opam/menhirLib.20211125/opam
+++ b/compiler/esy.lock/opam/menhirLib.20220210/opam
@@ -1,3 +1,4 @@
+
 opam-version: "2.0"
 maintainer: "francois.pottier@inria.fr"
 authors: [
@@ -21,9 +22,9 @@ conflicts: [
 synopsis: "Runtime support library for parsers generated by Menhir"
 url {
   src:
-    "https://gitlab.inria.fr/fpottier/menhir/-/archive/20211125/archive.tar.gz"
+    "https://gitlab.inria.fr/fpottier/menhir/-/archive/20220210/archive.tar.gz"
   checksum: [
-    "md5=27ddfc9be183d6ae8f5440d807c68e38"
-    "sha512=6f09d3008414b652aeee1387c712420635debb1e32539b17a7865805a7d4cf6c8d7dab8d5c6d4c583145f3f2fab07524ae64a832683ad64e832b80557d7526f9"
+    "md5=e3cef220f676c4b1c16cbccb174cefe3"
+    "sha512=3063fec1d8b9fe092c8461b0689d426c7fe381a2bf3fd258dc42ceecca1719d32efbb8a18d94ada5555c38175ea352da3adbb239fdbcbcf52c3a5c85a4d9586f"
   ]
 }
diff --git a/compiler/esy.lock/opam/menhirSdk.20211125/opam b/compiler/esy.lock/opam/menhirSdk.20220210/opam
similarity index 73%
rename from compiler/esy.lock/opam/menhirSdk.20211125/opam
rename to compiler/esy.lock/opam/menhirSdk.20220210/opam
index 8feb958d86..585d2ca330 100644
--- a/compiler/esy.lock/opam/menhirSdk.20211125/opam
+++ b/compiler/esy.lock/opam/menhirSdk.20220210/opam
@@ -1,3 +1,4 @@
+
 opam-version: "2.0"
 maintainer: "francois.pottier@inria.fr"
 authors: [
@@ -21,9 +22,9 @@ conflicts: [
 synopsis: "Compile-time library for auxiliary tools related to Menhir"
 url {
   src:
-    "https://gitlab.inria.fr/fpottier/menhir/-/archive/20211125/archive.tar.gz"
+    "https://gitlab.inria.fr/fpottier/menhir/-/archive/20220210/archive.tar.gz"
   checksum: [
-    "md5=27ddfc9be183d6ae8f5440d807c68e38"
-    "sha512=6f09d3008414b652aeee1387c712420635debb1e32539b17a7865805a7d4cf6c8d7dab8d5c6d4c583145f3f2fab07524ae64a832683ad64e832b80557d7526f9"
+    "md5=e3cef220f676c4b1c16cbccb174cefe3"
+    "sha512=3063fec1d8b9fe092c8461b0689d426c7fe381a2bf3fd258dc42ceecca1719d32efbb8a18d94ada5555c38175ea352da3adbb239fdbcbcf52c3a5c85a4d9586f"
   ]
 }
diff --git a/compiler/esy.lock/opam/num.1.4/opam b/compiler/esy.lock/opam/num.1.4/opam
index 253f84e024..0cea40c1e0 100644
--- a/compiler/esy.lock/opam/num.1.4/opam
+++ b/compiler/esy.lock/opam/num.1.4/opam
@@ -10,7 +10,10 @@ depends: [
   "ocaml" {>= "4.06.0"}
   "ocamlfind" {build & >= "1.7.3"}
 ]
-conflicts: ["base-num"]
+conflicts: [
+  "base-num"
+  "ocaml-option-bytecode-only"
+]
 build: make
 install: [
   ["ocamlfind" "remove" "num"]
diff --git a/compiler/esy.lock/opam/ppx_deriving.5.2.1/opam b/compiler/esy.lock/opam/ppx_deriving.5.2.1/opam
index ea9c3c61f4..f6197c6ffa 100644
--- a/compiler/esy.lock/opam/ppx_deriving.5.2.1/opam
+++ b/compiler/esy.lock/opam/ppx_deriving.5.2.1/opam
@@ -10,7 +10,7 @@ tags: [ "syntax" ]
 build: [
   ["dune" "subst"] {dev}
   ["dune" "build" "-p" name "-j" jobs]
-  ["dune" "runtest" "-p" name "-j" jobs] {with-test}
+  ["dune" "runtest" "-p" name "-j" jobs] {with-test & ocaml:version < "5.0.0"}
   ["dune" "build" "@doc" "-p" name "-j" jobs] {with-doc}
 ]
 depends: [
diff --git a/compiler/esy.lock/opam/topkg.1.0.6/opam b/compiler/esy.lock/opam/topkg.1.0.7/opam
similarity index 89%
rename from compiler/esy.lock/opam/topkg.1.0.6/opam
rename to compiler/esy.lock/opam/topkg.1.0.7/opam
index d8c8d66195..83fc06f492 100644
--- a/compiler/esy.lock/opam/topkg.1.0.6/opam
+++ b/compiler/esy.lock/opam/topkg.1.0.7/opam
@@ -41,7 +41,7 @@ depends: [
 build: ["ocaml" "pkg/pkg.ml" "build" "--pkg-name" name "--dev-pkg" "%{dev}%"]
 dev-repo: "git+https://erratique.ch/repos/topkg.git"
 url {
-  src: "https://erratique.ch/software/topkg/releases/topkg-1.0.6.tbz"
+  src: "https://erratique.ch/software/topkg/releases/topkg-1.0.7.tbz"
   checksum:
-    "sha512=8e34391e2f499cec332b79454a4edb36a35db6fe22437f017fd5c80ae065160dc967ac02d894a94d08d62dd476521e63733f4cadc3b9b6b314b6aa5b2b4ede78"
+    "sha512=09e59f1759bf4db8471f02d0aefd8db602b44932a291c05c312b1423796e7a15d1598d3c62a0cec7f083eff8e410fac09363533dc4bd2120914bb9664efea535"
 }
\ No newline at end of file
diff --git a/compiler/esy.lock/opam/utop.2.10.0/opam b/compiler/esy.lock/opam/utop.2.11.0/opam
similarity index 77%
rename from compiler/esy.lock/opam/utop.2.10.0/opam
rename to compiler/esy.lock/opam/utop.2.11.0/opam
index dbd68fd498..d9f71c3cdb 100644
--- a/compiler/esy.lock/opam/utop.2.10.0/opam
+++ b/compiler/esy.lock/opam/utop.2.11.0/opam
@@ -6,7 +6,7 @@ homepage: "https://github.com/ocaml-community/utop"
 bug-reports: "https://github.com/ocaml-community/utop/issues"
 doc: "https://ocaml-community.github.io/utop/"
 depends: [
-  "ocaml" {>= "4.03.0"}
+  "ocaml" {>= "4.08.0"}
   "base-unix"
   "base-threads"
   "ocamlfind" {>= "1.7.2"}
@@ -34,10 +34,10 @@ and more.  It integrates with the Tuareg mode in Emacs.
 """
 url {
   src:
-    "https://github.com/ocaml-community/utop/releases/download/2.10.0/utop-2.10.0.tbz"
+    "https://github.com/ocaml-community/utop/releases/download/2.11.0/utop-2.11.0.tbz"
   checksum: [
-    "sha256=475d16a2f9ea61c602ac32673ee210c76cc768f7214987d70c069532c2782d00"
-    "sha512=becbbc3b6651978bc6729631ec8a17a4e93e21d85b00af499f10caa9553166378190e6f1b2495ce4b8c2b5952f315ca88923a761067de47b614ed16d0f0d77c4"
+    "sha256=6937c6c672913ac3b875341ac4a205c7561d01cd8ac8f47cfb35d3bc0e762170"
+    "sha512=ab8b96eaa7f24654a371245f14819b74de0907ed8f3b2bbd9196808dc10e536458cf95418eeacf6dfc4b7f64a8dd088ee31e2eaae3d9ebc7de7cebcada52fb84"
   ]
 }
-x-commit-hash: "e56a75d2826fbe0ba3bc27a6d19fe08e02c3216d"
+x-commit-hash: "595002e6f07e6a3c6abc6e94a1b2448006115f1b"
diff --git a/compiler/graindoc/docblock.re b/compiler/graindoc/docblock.re
index 7b44f13504..576061296e 100644
--- a/compiler/graindoc/docblock.re
+++ b/compiler/graindoc/docblock.re
@@ -8,7 +8,7 @@ type t = {
   name: string,
   type_sig: string,
   description: option(string),
-  attributes: list(Comments.Attribute.t),
+  attributes: Comments.Attribute.attributes,
 };
 
 exception
@@ -163,7 +163,7 @@ let for_value_description =
 
   let (args, returns) = types_for_function(~ident, vd);
   // This replaces the default `None` for `attr_type` on `Param` and `Returns` attributes
-  let apply_types: (int, Comments.Attribute.t) => Comments.Attribute.t =
+  let apply_types: (int, Comment_attributes.t) => Comment_attributes.t =
     (idx, attr) => {
       switch (attr) {
       | Param(attr) =>
@@ -252,7 +252,7 @@ let to_markdown = (~current_version, docblock) => {
   let deprecations =
     docblock.attributes
     |> List.filter(Comments.Attribute.is_deprecated)
-    |> List.map((attr: Comments.Attribute.t) => {
+    |> List.map((attr: Comment_attributes.t) => {
          switch (attr) {
          | Deprecated({attr_desc}) => attr_desc
          | _ =>
@@ -275,7 +275,7 @@ let to_markdown = (~current_version, docblock) => {
   let since_attr =
     docblock.attributes
     |> List.find_opt(Comments.Attribute.is_since)
-    |> Option.map((attr: Comments.Attribute.t) => {
+    |> Option.map((attr: Comment_attributes.t) => {
          switch (attr) {
          | Since({attr_version}) =>
            output_for_since(~current_version, attr_version)
@@ -286,7 +286,7 @@ let to_markdown = (~current_version, docblock) => {
   let history_attrs =
     docblock.attributes
     |> List.filter(Comments.Attribute.is_history)
-    |> List.map((attr: Comments.Attribute.t) => {
+    |> List.map((attr: Comment_attributes.t) => {
          switch (attr) {
          | History({attr_version, attr_desc}) =>
            output_for_history(~current_version, attr_version, attr_desc)
@@ -315,7 +315,7 @@ let to_markdown = (~current_version, docblock) => {
   let params =
     docblock.attributes
     |> List.filter(Comments.Attribute.is_param)
-    |> List.map((attr: Comments.Attribute.t) => {
+    |> List.map((attr: Comment_attributes.t) => {
          switch (attr) {
          | Param({attr_name, attr_type, attr_desc}) => [
              Markdown.code(attr_name),
@@ -336,7 +336,7 @@ let to_markdown = (~current_version, docblock) => {
   let returns =
     docblock.attributes
     |> List.filter(Comments.Attribute.is_returns)
-    |> List.map((attr: Comments.Attribute.t) => {
+    |> List.map((attr: Comment_attributes.t) => {
          switch (attr) {
          | Returns({attr_type, attr_desc}) => [
              Option.fold(~none="", ~some=Markdown.code, attr_type),
@@ -357,7 +357,7 @@ let to_markdown = (~current_version, docblock) => {
     docblock.attributes
     |> List.filter(Comments.Attribute.is_throws)
     |> List.fold_left(
-         (map, attr: Comments.Attribute.t) => {
+         (map, attr: Comment_attributes.t) => {
            switch (attr) {
            | Throws({attr_type: Some(attr_type), attr_desc}) =>
              StringMap.update(
@@ -400,7 +400,7 @@ let to_markdown = (~current_version, docblock) => {
   let examples =
     docblock.attributes
     |> List.filter(Comments.Attribute.is_example)
-    |> List.map((attr: Comments.Attribute.t) => {
+    |> List.map((attr: Comment_attributes.t) => {
          switch (attr) {
          | Example({attr_desc}) => attr_desc
          | _ =>
diff --git a/compiler/graindoc/graindoc.re b/compiler/graindoc/graindoc.re
index f89478927f..1e2d88467d 100644
--- a/compiler/graindoc/graindoc.re
+++ b/compiler/graindoc/graindoc.re
@@ -100,7 +100,7 @@ let generate_docs =
     let deprecations =
       attrs
       |> List.filter(Comments.Attribute.is_deprecated)
-      |> List.map((attr: Comments.Attribute.t) => {
+      |> List.map((attr: Comment_attributes.t) => {
            switch (attr) {
            | Deprecated({attr_desc}) => attr_desc
            | _ =>
@@ -130,7 +130,7 @@ let generate_docs =
     let since_attr =
       attrs
       |> List.find_opt(Comments.Attribute.is_since)
-      |> Option.map((attr: Comments.Attribute.t) => {
+      |> Option.map((attr: Comment_attributes.t) => {
            switch (attr) {
            | Since({attr_version}) =>
              Docblock.output_for_since(~current_version, attr_version)
@@ -141,7 +141,7 @@ let generate_docs =
     let history_attrs =
       attrs
       |> List.filter(Comments.Attribute.is_history)
-      |> List.map((attr: Comments.Attribute.t) => {
+      |> List.map((attr: Comment_attributes.t) => {
            switch (attr) {
            | History({attr_version, attr_desc}) =>
              Docblock.output_for_history(
@@ -168,7 +168,7 @@ let generate_docs =
     let example_attrs = attrs |> List.filter(Comments.Attribute.is_example);
     if (List.length(example_attrs) > 0) {
       List.iter(
-        (attr: Comments.Attribute.t) => {
+        (attr: Comment_attributes.t) => {
           switch (attr) {
           | Example({attr_desc}) =>
             Buffer.add_string(buf, Markdown.code_block(attr_desc))
@@ -218,7 +218,7 @@ let generate_docs =
             next_section_start_line,
           );
         List.iter(
-          (attr: Comments.Attribute.t) => {
+          (attr: Comment_attributes.t) => {
             switch (attr) {
             | Section({attr_name, attr_desc}) =>
               Buffer.add_string(buf, Markdown.heading(~level=2, attr_name));
diff --git a/compiler/package.json b/compiler/package.json
index 2c900bfa20..5a84c2673c 100644
--- a/compiler/package.json
+++ b/compiler/package.json
@@ -31,6 +31,11 @@
     "parser:list-errors": "esy b menhir src/parsing/parser.mly --unused-tokens --list-errors > src/parsing/parser.messages.generated",
     "parser:update-errors": "esy b menhir src/parsing/parser.mly --unused-tokens --update-errors src/parsing/parser.messages > src/parsing/parser.messages.generated && cp src/parsing/parser.messages.generated src/parsing/parser.messages",
     "parser:check-errors": "npm run parser:list-errors && esy b menhir src/parsing/parser.mly --unused-tokens --compare-errors src/parsing/parser.messages.generated --compare-errors src/parsing/parser.messages",
+    "graindoc-parser:interpret": "esy b menhir src/diagnostics/graindoc_parser.mly --unused-tokens --interpret",
+    "graindoc-parser:interpret-error": "esy b menhir src/diagnostics/graindoc_parser.mly --unused-tokens --interpret-error",
+    "graindoc-parser:list-errors": "esy b menhir src/diagnostics/graindoc_parser.mly --unused-tokens --list-errors > src/diagnostics/graindoc_parser.messages.generated",
+    "graindoc-parser:update-errors": "esy b menhir src/diagnostics/graindoc_parser.mly --unused-tokens --update-errors src/diagnostics/graindoc_parser.messages > src/diagnostics/graindoc_parser.messages.generated && cp src/diagnostics/graindoc_parser.messages.generated src/diagnostics/graindoc_parser.messages",
+    "graindoc-parser:check-errors": "npm run graindoc-parser:list-errors && esy b menhir src/diagnostics/graindoc_parser.mly --unused-tokens --compare-errors src/diagnostics/graindoc_parser.messages.generated --compare-errors src/diagnostics/graindoc_parser.messages",
     "import-dependencies": "esy import-dependencies _export",
     "export-dependencies": "esy export-dependencies",
     "build-dependencies": "esy build-dependencies"
diff --git a/compiler/src/diagnostics/comment_attributes.re b/compiler/src/diagnostics/comment_attributes.re
new file mode 100644
index 0000000000..b56ae56307
--- /dev/null
+++ b/compiler/src/diagnostics/comment_attributes.re
@@ -0,0 +1,37 @@
+exception InvalidAttribute(string);
+exception MalformedAttribute(string, string);
+
+type attr_name = string;
+type attr_desc = string;
+// The `attr_type` always starts as `None` and is applied later by something like Graindoc
+type attr_type = option(string);
+type attr_version = string;
+
+type t =
+  | Param({
+      attr_name,
+      attr_type,
+      attr_desc,
+    })
+  | Returns({
+      attr_desc,
+      attr_type,
+    })
+  // Currently only accepts single-line examples
+  | Example({attr_desc})
+  | Section({
+      attr_name,
+      attr_desc,
+    })
+  | Deprecated({attr_desc})
+  | Since({attr_version})
+  | History({
+      attr_version,
+      attr_desc,
+    })
+  | Throws({
+      attr_type,
+      attr_desc,
+    });
+
+type parsed_graindoc = (option(string), list(t));
diff --git a/compiler/src/diagnostics/comments.re b/compiler/src/diagnostics/comments.re
index e5be786d5e..c28153e825 100644
--- a/compiler/src/diagnostics/comments.re
+++ b/compiler/src/diagnostics/comments.re
@@ -4,253 +4,121 @@ open Grain_utils;
 
 // Attributes in a comment are prefixed with `@` symbol, such as `@param`
 module Attribute = {
-  exception InvalidAttribute(string);
-  exception MalformedAttribute(string, string);
-
-  type attr_name = string;
-  type attr_desc = string;
-  // The `attr_type` always starts as `None` and is applied later by something like Graindoc
-  type attr_type = option(string);
-  type attr_version = string;
-
-  type t =
-    | Param({
-        attr_name,
-        attr_type,
-        attr_desc,
-      })
-    | Returns({
-        attr_desc,
-        attr_type,
-      })
-    // Currently only accepts single-line examples
-    | Example({attr_desc})
-    | Section({
-        attr_name,
-        attr_desc,
-      })
-    | Deprecated({attr_desc})
-    | Since({attr_version})
-    | History({
-        attr_version,
-        attr_desc,
-      })
-    | Throws({
-        attr_type,
-        attr_desc,
-      });
-
-  let parse_param = (~attr, content) => {
-    let re = Str.regexp({|^\([^:]+\):[ ]+\(.+\)$|});
-    if (Str.string_match(re, content, 0)) {
-      let attr_name = Str.matched_group(1, content);
-      let attr_desc = Str.matched_group(2, content);
-      Param({attr_name, attr_desc, attr_type: None});
-    } else {
-      raise(
-        MalformedAttribute(
-          attr,
-          "@param ParamName: Description of param value",
-        ),
-      );
-    };
-  };
+  open Comment_attributes;
 
-  let parse_returns = (~attr, content) => {
-    let re = Str.regexp({|^\(.+\)$|});
-    if (Str.string_match(re, content, 0)) {
-      let attr_desc = Str.matched_group(1, content);
-      Returns({attr_desc, attr_type: None});
-    } else {
-      raise(
-        MalformedAttribute(attr, "@returns Description of return value"),
-      );
-    };
-  };
+  type attributes = list(t);
 
-  let parse_example = (~attr, content) => {
-    let re = Str.regexp({|^\(.+\)$|});
-    if (Str.string_match(re, content, 0)) {
-      let attr_desc = Str.matched_group(1, content);
-      Example({attr_desc: attr_desc});
-    } else {
-      raise(MalformedAttribute(attr, "@example single-line code example"));
-    };
-  };
+  type error =
+    | GraindocSyntaxError(string, string);
 
-  let parse_section = (~attr, content) => {
-    let re = Str.regexp({|^\([^:]+\):[ ]+\(.+\)$|});
-    if (Str.string_match(re, content, 0)) {
-      let attr_name = Str.matched_group(1, content);
-      let attr_desc = Str.matched_group(2, content);
-      Section({attr_name, attr_desc});
-    } else {
-      raise(
-        MalformedAttribute(
-          attr,
-          "@section SectionName: Description of section",
-        ),
-      );
+  exception Error(Location.t, error);
+
+  let report_error = (ppf, err) =>
+    switch (err) {
+    | GraindocSyntaxError(msg, where) =>
+      Format.fprintf(ppf, "Graindoc syntax error %s: %s", where, msg)
     };
-  };
 
-  let parse_deprecated = (~attr, content) => {
-    let re = Str.regexp({|^\(.+\)$|});
-    if (Str.string_match(re, content, 0)) {
-      let attr_desc = Str.matched_group(1, content);
-      Deprecated({attr_desc: attr_desc});
-    } else {
-      raise(
-        MalformedAttribute(attr, "@deprecated Description of deprecation"),
+  let () =
+    Location.register_error_of_exn(
+      fun
+      | Error(loc, err) =>
+        Some(Location.error_of_printer(loc, report_error, err))
+      | _ => None,
+    );
+
+  let extract = (comment_source, comment_content, comment_loc) => {
+    // strip trailing */ to allow block comments in examples
+    let modified_source =
+      String.trim(
+        Grain_utils.String_utils.slice(~first=0, ~last=-2, comment_source),
       );
-    };
-  };
+    let lexbuf = Sedlexing.Utf8.from_string(modified_source);
 
-  let parse_since = (~attr, content) => {
-    let re = Str.regexp({|^v?\([0-9]+\.[0-9]+\.[0-9]+\)$|});
-    if (Str.string_match(re, content, 0)) {
-      let attr_version = Str.matched_group(1, content);
-      Since({attr_version: attr_version});
-    } else {
-      raise(MalformedAttribute(attr, "@since vX.Y.Z"));
-    };
-  };
+    Sedlexing.set_position(lexbuf, comment_loc.Location.loc_start);
+    Sedlexing.set_filename(lexbuf, comment_loc.Location.loc_start.pos_fname);
 
-  let parse_history = (~attr, content) => {
-    let re = Str.regexp({|^v?\([0-9]+\.[0-9]+\.[0-9]+\):[ ]+\(.+\)$|});
-    if (Str.string_match(re, content, 0)) {
-      let attr_version = Str.matched_group(1, content);
-      let attr_desc = Str.matched_group(2, content);
-      History({attr_version, attr_desc});
-    } else {
-      raise(
-        MalformedAttribute(attr, "@history vX.Y.Z: Description of history"),
+    let parse_graindoc =
+      MenhirLib.Convert.Simplified.traditional2revised(
+        Graindoc_parser.graindoc,
+      );
+    let (buffer, graindoc_lexer) =
+      MenhirLib.ErrorReports.wrap_supplier(
+        Sedlexing.with_tokenizer(Graindoc_lexer.make_lexer(), lexbuf),
       );
-    };
-  };
 
-  let parse_throws = (~attr, content) => {
-    let re = Str.regexp({|^\([^:]+\):[ ]+\(.+\)$|});
-    if (Str.string_match(re, content, 0)) {
-      let attr_type = Str.matched_group(1, content);
-      let attr_desc = Str.matched_group(2, content);
-      Throws({attr_type: Some(attr_type), attr_desc});
-    } else {
+    try(parse_graindoc(graindoc_lexer)) {
+    | Graindoc_parser.Error(state) =>
+      open Lexing;
+      let chunk = ((start_p, end_p)) =>
+        String_utils.Utf8.sub(
+          comment_source,
+          start_p.pos_cnum - comment_loc.loc_start.pos_cnum,
+          end_p.pos_cnum - start_p.pos_cnum,
+        );
+      let where = MenhirLib.ErrorReports.show(chunk, buffer);
       raise(
-        MalformedAttribute(
-          attr,
-          "@throws ExceptionType: Explanation of exceptional case",
+        Error(
+          Location.curr(lexbuf),
+          GraindocSyntaxError(
+            Graindoc_parser_messages.message(state),
+            where,
+          ),
         ),
       );
     };
   };
 
-  let extract = comment => {
-    let attrs = ref([]);
-    let attr_line_re = Str.regexp({|^@\([a-zA-Z_]+\)\b\(.*\)$|});
-
-    // TODO: We should probably transition to a lexer, instead of 2-passes of RegExp
-    let out =
-      Str.global_substitute(
-        attr_line_re,
-        _ => {
-          let attr = Str.matched_group(1, comment);
-          // Trim this since we only match word boundaries now
-          let content = String.trim(Str.matched_group(2, comment));
-          switch (attr) {
-          | "param" =>
-            let param_attr = parse_param(~attr, content);
-            attrs := [param_attr, ...attrs^];
-          | "returns" =>
-            let returns_attr = parse_returns(~attr, content);
-            attrs := [returns_attr, ...attrs^];
-          | "example" =>
-            let example_attr = parse_example(~attr, content);
-            attrs := [example_attr, ...attrs^];
-          | "section" =>
-            let section_attr = parse_section(~attr, content);
-            attrs := [section_attr, ...attrs^];
-          | "deprecated" =>
-            let deprecated_attr = parse_deprecated(~attr, content);
-            attrs := [deprecated_attr, ...attrs^];
-          | "since" =>
-            let since_attr = parse_since(~attr, content);
-            attrs := [since_attr, ...attrs^];
-          | "history" =>
-            let history_attr = parse_history(~attr, content);
-            attrs := [history_attr, ...attrs^];
-          | "throws" =>
-            let throws_attr = parse_throws(~attr, content);
-            attrs := [throws_attr, ...attrs^];
-          | _ => raise(InvalidAttribute(attr))
-          };
-
-          // Replace it with nothing
-          "";
-        },
-        comment,
-      );
-
-    let desc = String.trim(out);
-    let desc_opt =
-      if (desc != "") {
-        Some(desc);
-      } else {
-        None;
-      };
-    (desc_opt, List.rev(attrs^));
-  };
-
-  let is_param = (attr: t) => {
+  let is_param = attr => {
     switch (attr) {
     | Param(_) => true
     | _ => false
     };
   };
 
-  let is_returns = (attr: t) => {
+  let is_returns = attr => {
     switch (attr) {
     | Returns(_) => true
     | _ => false
     };
   };
 
-  let is_example = (attr: t) => {
+  let is_example = attr => {
     switch (attr) {
     | Example(_) => true
     | _ => false
     };
   };
 
-  let is_section = (attr: t) => {
+  let is_section = attr => {
     switch (attr) {
     | Section(_) => true
     | _ => false
     };
   };
 
-  let is_deprecated = (attr: t) => {
+  let is_deprecated = attr => {
     switch (attr) {
     | Deprecated(_) => true
     | _ => false
     };
   };
 
-  let is_since = (attr: t) => {
+  let is_since = attr => {
     switch (attr) {
     | Since(_) => true
     | _ => false
     };
   };
 
-  let is_history = (attr: t) => {
+  let is_history = attr => {
     switch (attr) {
     | History(_) => true
     | _ => false
     };
   };
 
-  let is_throws = (attr: t) => {
+  let is_throws = attr => {
     switch (attr) {
     | Throws(_) => true
     | _ => false
@@ -281,7 +149,7 @@ module Attribute = {
 };
 
 type description = option(string);
-type attributes = list(Attribute.t);
+type attributes = Attribute.attributes;
 
 module type OrderedComments = {
   type comment = (Typedtree.comment, description, attributes);
@@ -321,8 +189,9 @@ module MakeOrderedComments =
         | Block({cmt_loc, _}) =>
           let data = (comment, None, []);
           (cmt_loc.loc_start.pos_lnum, cmt_loc.loc_end.pos_lnum, data);
-        | Doc({cmt_loc, cmt_content}) =>
-          let (description, attributes) = Attribute.extract(cmt_content);
+        | Doc({cmt_source, cmt_content, cmt_loc}) =>
+          let (description, attributes) =
+            Attribute.extract(cmt_source, cmt_content, cmt_loc);
           let data = (comment, description, attributes);
           (cmt_loc.loc_start.pos_lnum, cmt_loc.loc_end.pos_lnum, data);
         };
diff --git a/compiler/src/diagnostics/dune b/compiler/src/diagnostics/dune
index d8c8eda563..8c9fe95dbc 100644
--- a/compiler/src/diagnostics/dune
+++ b/compiler/src/diagnostics/dune
@@ -1,8 +1,19 @@
+(menhir
+ (modules graindoc_parser)
+ (flags --explain --unused-tokens --exn-carries-state --strict))
+
+(rule
+ (action
+  (with-stdout-to
+   graindoc_parser_messages.ml
+   (run menhir %{dep:graindoc_parser.mly} --compile-errors
+     %{dep:graindoc_parser.messages} --unused-tokens))))
+
 (library
  (name grain_diagnostics)
  (public_name grain_diagnostics)
  (synopsis "Diagnostic modules for Grain compiler")
  (libraries compiler-libs.common grain_utils grain_typed str
-   ppx_deriving_yojson.runtime yojson)
+   ppx_deriving_yojson.runtime yojson menhirLib sexplib)
  (preprocess
-  (pps ppx_deriving_yojson)))
+  (pps ppx_deriving_yojson sedlex.ppx)))
diff --git a/compiler/src/diagnostics/graindoc_lexer.re b/compiler/src/diagnostics/graindoc_lexer.re
new file mode 100644
index 0000000000..0429fdc4ff
--- /dev/null
+++ b/compiler/src/diagnostics/graindoc_lexer.re
@@ -0,0 +1,213 @@
+open Grain_parsing;
+open Graindoc_parser;
+
+let lexbuf_loc = lexbuf => {
+  let (loc_start, loc_end) = Sedlexing.lexing_positions(lexbuf);
+  Location.{loc_start, loc_end, loc_ghost: false};
+};
+
+let ident = [%sedlex.regexp? (xid_start | '_', Star(xid_continue))];
+let semver = [%sedlex.regexp?
+  (
+    Opt('v'),
+    Plus('0' .. '9'),
+    '.',
+    Plus('0' .. '9'),
+    '.',
+    Plus('0' .. '9'),
+    Opt((
+      '-',
+      Star('0' .. '9' | 'A' .. 'z' | '-' | '.'),
+      Opt(('+', Star('0' .. '9' | 'A' .. 'z' | '-'))),
+    )),
+  )
+];
+
+let normalize_semver = semver =>
+  if (semver.[0] == 'v') {
+    Grain_utils.String_utils.slice(
+      ~first=1,
+      ~last=String.length(semver),
+      semver,
+    );
+  } else {
+    semver;
+  };
+
+// HORIZONTAL TABULATION
+// VERTICAL TABULATION
+// SPACE
+// LEFT-TO-RIGHT MARK
+// RIGHT-TO-LEFT MARK
+let blank = [%sedlex.regexp? 0x09 | 0x0B | 0x20 | 0x200E | 0x200F];
+
+// LINE FEED
+// FORM FEED
+// CARRIAGE RETURN
+// NEXT LINE
+// LINE SEPARATOR
+// PARAGRAPH SEPARATOR
+let newline = [%sedlex.regexp? 0x0A | 0x0C | 0x0D | 0x85 | 0x2028 | 0x2029];
+
+// A colon eats whitespace after it
+let colon = [%sedlex.regexp? (':', Star(blank))];
+
+// A asterisk eats whitespace before it and up to 1 after it
+let asterisk = [%sedlex.regexp? (Star(blank), '*', Opt(blank))];
+
+type lexer_state = {mutable lexer_mode}
+and lexer_mode =
+  | Start
+  | Default
+  | Param
+  | Section
+  | Since
+  | History
+  | Throws
+  | FreeTextAttribute;
+
+let rec token = (state, lexbuf) => {
+  switch (state.lexer_mode) {
+  | Start => start(state, lexbuf)
+  | Default => default(state, lexbuf)
+  | Param => param(state, lexbuf)
+  | Section => section(state, lexbuf)
+  | Since => since(state, lexbuf)
+  | History => history(state, lexbuf)
+  | Throws => throws(state, lexbuf)
+  | FreeTextAttribute => free_text_attribute(state, lexbuf)
+  };
+}
+
+and start = (state, lexbuf) => {
+  switch%sedlex (lexbuf) {
+  | ("/**", Star(blank)) =>
+    state.lexer_mode = Default;
+    default(state, lexbuf);
+  | _ =>
+    state.lexer_mode = Default;
+    default(state, lexbuf);
+  };
+}
+
+and default = (state, lexbuf) => {
+  switch%sedlex (lexbuf) {
+  | asterisk => default(state, lexbuf)
+  | "@param" =>
+    state.lexer_mode = Param;
+    PARAM;
+  | "@returns" =>
+    state.lexer_mode = FreeTextAttribute;
+    RETURNS;
+  | "@example" =>
+    state.lexer_mode = FreeTextAttribute;
+    EXAMPLE;
+  | "@section" =>
+    state.lexer_mode = Section;
+    SECTION;
+  | "@deprecated" =>
+    state.lexer_mode = FreeTextAttribute;
+    DEPRECATED;
+  | "@since" =>
+    state.lexer_mode = Since;
+    SINCE;
+  | "@history" =>
+    state.lexer_mode = History;
+    HISTORY;
+  | "@throws" =>
+    state.lexer_mode = Throws;
+    THROWS;
+  | newline => EOL
+  | eof => EOF
+  | _ => text(state, lexbuf)
+  };
+}
+
+and free_text_attribute = (state, lexbuf) => {
+  switch%sedlex (lexbuf) {
+  | blank => free_text_attribute(state, lexbuf)
+  | _ =>
+    state.lexer_mode = Default;
+    default(state, lexbuf);
+  };
+}
+
+and param = (state, lexbuf) => {
+  switch%sedlex (lexbuf) {
+  | blank => param(state, lexbuf)
+  | ident => IDENT(Sedlexing.Utf8.lexeme(lexbuf))
+  | colon =>
+    state.lexer_mode = Default;
+    COLON;
+  | _ =>
+    state.lexer_mode = Default;
+    default(state, lexbuf);
+  };
+}
+
+and section = (state, lexbuf) => {
+  switch%sedlex (lexbuf) {
+  | blank => section(state, lexbuf)
+  | (Compl(blank | newline | ':' | eof), Star(Compl(newline | ':' | eof))) =>
+    TEXT(Sedlexing.Utf8.lexeme(lexbuf))
+  | colon =>
+    state.lexer_mode = Default;
+    COLON;
+  | _ =>
+    state.lexer_mode = Default;
+    default(state, lexbuf);
+  };
+}
+
+and since = (state, lexbuf) => {
+  switch%sedlex (lexbuf) {
+  | blank => since(state, lexbuf)
+  | semver =>
+    state.lexer_mode = Default;
+    SEMVER(normalize_semver(Sedlexing.Utf8.lexeme(lexbuf)));
+  | _ =>
+    state.lexer_mode = Default;
+    default(state, lexbuf);
+  };
+}
+
+and history = (state, lexbuf) => {
+  switch%sedlex (lexbuf) {
+  | blank => history(state, lexbuf)
+  | semver => SEMVER(normalize_semver(Sedlexing.Utf8.lexeme(lexbuf)))
+  | colon =>
+    state.lexer_mode = Default;
+    COLON;
+  | _ =>
+    state.lexer_mode = Default;
+    default(state, lexbuf);
+  };
+}
+
+and throws = (state, lexbuf) => {
+  switch%sedlex (lexbuf) {
+  | blank => throws(state, lexbuf)
+  | (Compl(blank | newline | ':' | eof), Star(Compl(newline | ':' | eof))) =>
+    CONSTRUCTOR(Sedlexing.Utf8.lexeme(lexbuf))
+  | colon =>
+    state.lexer_mode = Default;
+    COLON;
+  | _ =>
+    state.lexer_mode = Default;
+    default(state, lexbuf);
+  };
+}
+
+and text = (state, lexbuf) => {
+  switch%sedlex (lexbuf) {
+  | Plus(Compl(newline | eof)) => TEXT(Sedlexing.Utf8.lexeme(lexbuf))
+  | _ =>
+    state.lexer_mode = Default;
+    default(state, lexbuf);
+  };
+};
+
+let make_lexer = () => {
+  let state = {lexer_mode: Start};
+  lexbuf => token(state, lexbuf);
+};
diff --git a/compiler/src/diagnostics/graindoc_parser.messages b/compiler/src/diagnostics/graindoc_parser.messages
new file mode 100644
index 0000000000..3dea2af3ed
--- /dev/null
+++ b/compiler/src/diagnostics/graindoc_parser.messages
@@ -0,0 +1,278 @@
+graindoc: SEMVER
+##
+## Ends in an error in state: 0.
+##
+## graindoc' -> . graindoc [ # ]
+##
+## The known suffix of the stack is as follows:
+##
+##
+
+Expected a description or Graindoc attribute.
+
+graindoc: TEXT TEXT
+##
+## Ends in an error in state: 4.
+##
+## description -> multiline_text_help . [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOF DEPRECATED ]
+## description -> multiline_text_help . eols [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOF DEPRECATED ]
+## multiline_text_help -> multiline_text_help . EOL TEXT [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+## multiline_text_help -> multiline_text_help . eols EOL TEXT [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+##
+## The known suffix of the stack is as follows:
+## multiline_text_help
+##
+graindoc: SINCE SEMVER TEXT
+##
+## Ends in an error in state: 42.
+##
+## attributes_help -> attributes_help . option(eols) attribute [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+## graindoc -> option(eols) description attributes_help . EOF [ # ]
+## graindoc -> option(eols) description attributes_help . eols EOF [ # ]
+##
+## The known suffix of the stack is as follows:
+## option(eols) description attributes_help
+##
+
+Expected a newline character.
+
+graindoc: TEXT EOL SEMVER
+##
+## Ends in an error in state: 5.
+##
+## eols -> EOL . [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+## multiline_text_help -> multiline_text_help EOL . TEXT [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+##
+## The known suffix of the stack is as follows:
+## multiline_text_help EOL
+##
+graindoc: TEXT EOL EOL SEMVER
+##
+## Ends in an error in state: 8.
+##
+## eols -> eols EOL . [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+## multiline_text_help -> multiline_text_help eols EOL . TEXT [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+##
+## The known suffix of the stack is as follows:
+## multiline_text_help eols EOL
+##
+graindoc: DEPRECATED TEXT TEXT
+##
+## Ends in an error in state: 14.
+##
+## attribute_text -> multiline_text_help . [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+## attribute_text -> multiline_text_help . eols [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+## multiline_text_help -> multiline_text_help . EOL TEXT [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+## multiline_text_help -> multiline_text_help . eols EOL TEXT [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+##
+## The known suffix of the stack is as follows:
+## multiline_text_help
+##
+graindoc: DEPRECATED EOL TEXT TEXT
+##
+## Ends in an error in state: 18.
+##
+## attribute_text -> eols multiline_text_help . [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+## attribute_text -> eols multiline_text_help . eols [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+## multiline_text_help -> multiline_text_help . EOL TEXT [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+## multiline_text_help -> multiline_text_help . eols EOL TEXT [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+##
+## The known suffix of the stack is as follows:
+## eols multiline_text_help
+##
+graindoc: SINCE SEMVER EOL TEXT
+##
+## Ends in an error in state: 46.
+##
+## eols -> eols . EOL [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+## graindoc -> option(eols) description attributes_help eols . EOF [ # ]
+## option(eols) -> eols . [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE DEPRECATED ]
+##
+## The known suffix of the stack is as follows:
+## option(eols) description attributes_help eols
+##
+graindoc: EOL SEMVER
+##
+## Ends in an error in state: 50.
+##
+## eols -> eols . EOL [ THROWS TEXT SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+## option(eols) -> eols . [ THROWS TEXT SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOF DEPRECATED ]
+##
+## The known suffix of the stack is as follows:
+## eols
+##
+
+Expected a Graindoc attribute, such as `@param`, `@returns`, or `@example`.
+
+graindoc: THROWS THROWS
+##
+## Ends in an error in state: 11.
+##
+## attribute -> THROWS . CONSTRUCTOR COLON attribute_text [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+##
+## The known suffix of the stack is as follows:
+## THROWS
+##
+
+Expected an exception constructor.
+
+graindoc: THROWS CONSTRUCTOR THROWS
+##
+## Ends in an error in state: 12.
+##
+## attribute -> THROWS CONSTRUCTOR . COLON attribute_text [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+##
+## The known suffix of the stack is as follows:
+## THROWS CONSTRUCTOR
+##
+graindoc: SECTION TEXT THROWS
+##
+## Ends in an error in state: 24.
+##
+## attribute -> SECTION TEXT . COLON attribute_text [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+##
+## The known suffix of the stack is as follows:
+## SECTION TEXT
+##
+graindoc: PARAM IDENT THROWS
+##
+## Ends in an error in state: 30.
+##
+## attribute -> PARAM IDENT . COLON attribute_text [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+##
+## The known suffix of the stack is as follows:
+## PARAM IDENT
+##
+graindoc: HISTORY SEMVER THROWS
+##
+## Ends in an error in state: 34.
+##
+## attribute -> HISTORY SEMVER . COLON attribute_text [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+##
+## The known suffix of the stack is as follows:
+## HISTORY SEMVER
+##
+
+Expected a colon.
+
+graindoc: THROWS CONSTRUCTOR COLON THROWS
+##
+## Ends in an error in state: 13.
+##
+## attribute -> THROWS CONSTRUCTOR COLON . attribute_text [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+##
+## The known suffix of the stack is as follows:
+## THROWS CONSTRUCTOR COLON
+##
+graindoc: DEPRECATED EOL THROWS
+##
+## Ends in an error in state: 16.
+##
+## attribute_text -> eols . multiline_text_help [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+## attribute_text -> eols . multiline_text_help eols [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+## eols -> eols . EOL [ TEXT EOL ]
+##
+## The known suffix of the stack is as follows:
+## eols
+##
+graindoc: SECTION TEXT COLON THROWS
+##
+## Ends in an error in state: 25.
+##
+## attribute -> SECTION TEXT COLON . attribute_text [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+##
+## The known suffix of the stack is as follows:
+## SECTION TEXT COLON
+##
+graindoc: RETURNS THROWS
+##
+## Ends in an error in state: 27.
+##
+## attribute -> RETURNS . attribute_text [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+##
+## The known suffix of the stack is as follows:
+## RETURNS
+##
+graindoc: PARAM IDENT COLON THROWS
+##
+## Ends in an error in state: 31.
+##
+## attribute -> PARAM IDENT COLON . attribute_text [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+##
+## The known suffix of the stack is as follows:
+## PARAM IDENT COLON
+##
+graindoc: HISTORY SEMVER COLON THROWS
+##
+## Ends in an error in state: 35.
+##
+## attribute -> HISTORY SEMVER COLON . attribute_text [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+##
+## The known suffix of the stack is as follows:
+## HISTORY SEMVER COLON
+##
+graindoc: EXAMPLE THROWS
+##
+## Ends in an error in state: 37.
+##
+## attribute -> EXAMPLE . attribute_text [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+##
+## The known suffix of the stack is as follows:
+## EXAMPLE
+##
+graindoc: DEPRECATED THROWS
+##
+## Ends in an error in state: 40.
+##
+## attribute -> DEPRECATED . attribute_text [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+##
+## The known suffix of the stack is as follows:
+## DEPRECATED
+##
+
+Expected a description.
+
+graindoc: SINCE THROWS
+##
+## Ends in an error in state: 21.
+##
+## attribute -> SINCE . SEMVER [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+##
+## The known suffix of the stack is as follows:
+## SINCE
+##
+graindoc: HISTORY THROWS
+##
+## Ends in an error in state: 33.
+##
+## attribute -> HISTORY . SEMVER COLON attribute_text [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+##
+## The known suffix of the stack is as follows:
+## HISTORY
+##
+
+Expected a version number in Semantic Versioning format, e.g. `v1.2.3`.
+
+graindoc: SECTION THROWS
+##
+## Ends in an error in state: 23.
+##
+## attribute -> SECTION . TEXT COLON attribute_text [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+##
+## The known suffix of the stack is as follows:
+## SECTION
+##
+
+Expected a section title.
+
+graindoc: PARAM THROWS
+##
+## Ends in an error in state: 29.
+##
+## attribute -> PARAM . IDENT COLON attribute_text [ THROWS SINCE SECTION RETURNS PARAM HISTORY EXAMPLE EOL EOF DEPRECATED ]
+##
+## The known suffix of the stack is as follows:
+## PARAM
+##
+
+Expected a parameter name.
diff --git a/compiler/src/diagnostics/graindoc_parser.mly b/compiler/src/diagnostics/graindoc_parser.mly
new file mode 100644
index 0000000000..a80cc1c1a1
--- /dev/null
+++ b/compiler/src/diagnostics/graindoc_parser.mly
@@ -0,0 +1,48 @@
+%token PARAM SECTION SINCE HISTORY THROWS RETURNS EXAMPLE DEPRECATED COLON EOL EOF
+%token <string> TEXT IDENT SEMVER CONSTRUCTOR
+
+%right EOL
+
+%start <Comment_attributes.parsed_graindoc> graindoc
+
+%%
+
+eols:
+  | EOL
+  | eols EOL {}
+
+multiline_text_help:
+  | TEXT { [$1] }
+  | multiline_text_help EOL TEXT { $3 :: "\n" :: $1 }
+  | multiline_text_help eols EOL TEXT { $4 :: "\n\n" :: $1 }
+
+%inline multiline_text:
+  | rev(multiline_text_help) { String.concat "" $1 }
+
+description:
+  | { None }
+  | multiline_text ioption(eols) { Some($1) }
+
+attribute_text:
+  | ioption(eols) multiline_text ioption(eols) %prec EOL { $2 }
+
+attribute:
+  | PARAM IDENT COLON attribute_text { Param({ attr_name=$2; attr_type=None; attr_desc=$4 }) }
+  | RETURNS attribute_text { Returns({ attr_desc=$2; attr_type=None }) }
+  | EXAMPLE attribute_text { Example({attr_desc=$2}) }
+  | SECTION TEXT COLON attribute_text { Section({ attr_name=$2; attr_desc=$4; }) }
+  | DEPRECATED attribute_text { Deprecated({attr_desc=$2}) }
+  | SINCE SEMVER { Since({attr_version=$2}) }
+  | HISTORY SEMVER COLON attribute_text { History({ attr_version=$2; attr_desc=$4; }) }
+  | THROWS CONSTRUCTOR COLON attribute_text { Throws({ attr_type=Some $2; attr_desc=$4; }); }
+
+attributes_help:
+  | attribute { [$1] }
+  | attributes_help option(eols) attribute { $3 :: $1 }
+
+%inline attributes:
+  | { [] }
+  | rev(attributes_help) ioption(eols) { $1 }
+
+graindoc:
+  | option(eols) description attributes EOF { ($2, $3) }