diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,3 @@
+# 0.1.0.0
+
+Initial version.
diff --git a/LICENSE b/LICENSE
new file mode 100644
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,202 @@
+
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
+      the Work and Derivative Works thereof.
+
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
+      submitted to Licensor for inclusion in the Work by the copyright owner
+      or by an individual or Legal Entity authorized to submit on behalf of
+      the copyright owner. For the purposes of this definition, "submitted"
+      means any form of electronic, verbal, or written communication sent
+      to the Licensor or its representatives, including but not limited to
+      communication on electronic mailing lists, source code control systems,
+      and issue tracking systems that are managed by, or on behalf of, the
+      Licensor for the purpose of discussing and improving the Work, but
+      excluding communication that is conspicuously marked or otherwise
+      designated in writing by the copyright owner as "Not a Contribution."
+
+      "Contributor" shall mean Licensor and any individual or Legal Entity
+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+
+   2. Grant of Copyright License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      copyright license to reproduce, prepare Derivative Works of,
+      publicly display, publicly perform, sublicense, and distribute the
+      Work and such Derivative Works in Source or Object form.
+
+   3. Grant of Patent License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      (except as stated in this section) patent license to make, have made,
+      use, offer to sell, sell, import, and otherwise transfer the Work,
+      where such license applies only to those patent claims licensable
+      by such Contributor that are necessarily infringed by their
+      Contribution(s) alone or by combination of their Contribution(s)
+      with the Work to which such Contribution(s) was submitted. If You
+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
+      or contributory patent infringement, then any patent licenses
+      granted to You under this License for that Work shall terminate
+      as of the date such litigation is filed.
+
+   4. Redistribution. You may reproduce and distribute copies of the
+      Work or Derivative Works thereof in any medium, with or without
+      modifications, and in Source or Object form, provided that You
+      meet the following conditions:
+
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
+
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+
+      (c) You must retain, in the Source form of any Derivative Works
+          that You distribute, all copyright, patent, trademark, and
+          attribution notices from the Source form of the Work,
+          excluding those notices that do not pertain to any part of
+          the Derivative Works; and
+
+      (d) If the Work includes a "NOTICE" text file as part of its
+          distribution, then any Derivative Works that You distribute must
+          include a readable copy of the attribution notices contained
+          within such NOTICE file, excluding those notices that do not
+          pertain to any part of the Derivative Works, in at least one
+          of the following places: within a NOTICE text file distributed
+          as part of the Derivative Works; within the Source form or
+          documentation, if provided along with the Derivative Works; or,
+          within a display generated by the Derivative Works, if and
+          wherever such third-party notices normally appear. The contents
+          of the NOTICE file are for informational purposes only and
+          do not modify the License. You may add Your own attribution
+          notices within Derivative Works that You distribute, alongside
+          or as an addendum to the NOTICE text from the Work, provided
+          that such additional attribution notices cannot be construed
+          as modifying the License.
+
+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
+      for use, reproduction, or distribution of Your modifications, or
+      for any such Derivative Works as a whole, provided Your use,
+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
+      origin of the Work and reproducing the content of the NOTICE file.
+
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+      implied, including, without limitation, any warranties or conditions
+      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
+      or other liability obligations and/or rights consistent with this
+      License. However, in accepting such obligations, You may act only
+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
+
+   END OF TERMS AND CONDITIONS
+
+   APPENDIX: How to apply the Apache License to your work.
+
+      To apply the Apache License to your work, attach the following
+      boilerplate notice, with the fields enclosed by brackets "[]"
+      replaced with your own identifying information. (Don't include
+      the brackets!)  The text should be enclosed in the appropriate
+      comment syntax for the file format. We also recommend that a
+      file or class name and description of purpose be included on the
+      same "printed page" as the copyright notice for easier
+      identification within third-party archives.
+
+   Copyright [yyyy] [name of copyright owner]
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
diff --git a/dependent-literals.cabal b/dependent-literals.cabal
new file mode 100644
--- /dev/null
+++ b/dependent-literals.cabal
@@ -0,0 +1,48 @@
+cabal-version: 1.12
+
+-- This file has been generated from package.yaml by hpack version 0.33.0.
+--
+-- see: https://github.com/sol/hpack
+--
+-- hash: 30f8fe2e48f6bbcd438d851405bf47990834dff8704739447c29c6398746aa0e
+
+name:           dependent-literals
+version:        0.1.0.0
+synopsis:       Provides library support for pseudo-dependently-typed int literals.
+description:    This is the library counterpart of
+                <https://hackage.haskell.org/package/dependent-literals-plugin dependent-literals-plugin>.
+                See that package's description for more details.
+category:       Constraints
+homepage:       https://github.com/google/hs-dependent-literals#readme
+bug-reports:    https://github.com/google/hs-dependent-literals/issues
+author:         Andrew Pritchard <awpr@google.com>
+maintainer:     Andrew Pritchard <awpr@google.com>
+copyright:      2019-2021 Google LLC
+license:        Apache-2.0
+license-file:   LICENSE
+build-type:     Simple
+extra-source-files:
+    CHANGELOG.md
+
+source-repository head
+  type: git
+  location: https://github.com/google/hs-dependent-literals
+  subdir: dependent-literals
+
+library
+  exposed-modules:
+      DependentLiterals
+      DependentLiterals.Bounds
+      DependentLiterals.Int
+  other-modules:
+      Paths_dependent_literals
+  hs-source-dirs:
+      src
+  build-depends:
+      base >=4.12 && <4.16
+    , fin-int >=0.1 && <0.2
+    , numeric-kinds >=0.1 && <0.2
+    , sint >=0.1 && <0.2
+    , snumber >=0.1 && <0.2
+    , tagged >=0.8 && <0.9
+  default-language: Haskell2010
diff --git a/src/DependentLiterals.hs b/src/DependentLiterals.hs
new file mode 100644
--- /dev/null
+++ b/src/DependentLiterals.hs
@@ -0,0 +1,29 @@
+-- Copyright 2020-2021 Google LLC
+--
+-- Licensed under the Apache License, Version 2.0 (the "License");
+-- you may not use this file except in compliance with the License.
+-- You may obtain a copy of the License at
+--
+--      http://www.apache.org/licenses/LICENSE-2.0
+--
+-- Unless required by applicable law or agreed to in writing, software
+-- distributed under the License is distributed on an "AS IS" BASIS,
+-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+-- See the License for the specific language governing permissions and
+-- limitations under the License.
+
+-- | Top-level module exporting the key DependentLiterals functionality.
+
+module DependentLiterals
+  ( -- * Int Literals
+    HasIntLiterals, AllowsIntLiteral, IntLiteral
+  , valueOf
+
+    -- ** Basic Literals
+  , HasBasicLiterals, StockLit(..)
+
+    -- ** Dependent Literals
+  , SNum(..), SNumLit(..)
+  ) where
+
+import DependentLiterals.Int
diff --git a/src/DependentLiterals/Bounds.hs b/src/DependentLiterals/Bounds.hs
new file mode 100644
--- /dev/null
+++ b/src/DependentLiterals/Bounds.hs
@@ -0,0 +1,116 @@
+-- Copyright 2020-2021 Google LLC
+--
+-- Licensed under the Apache License, Version 2.0 (the "License");
+-- you may not use this file except in compliance with the License.
+-- You may obtain a copy of the License at
+--
+--      http://www.apache.org/licenses/LICENSE-2.0
+--
+-- Unless required by applicable law or agreed to in writing, software
+-- distributed under the License is distributed on an "AS IS" BASIS,
+-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+-- See the License for the specific language governing permissions and
+-- limitations under the License.
+
+{-# LANGUAGE AllowAmbiguousTypes #-}
+{-# LANGUAGE ConstraintKinds #-}
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE DerivingVia #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE InstanceSigs #-}
+{-# LANGUAGE KindSignatures #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE PatternSynonyms #-}
+{-# LANGUAGE PolyKinds #-}
+{-# LANGUAGE RoleAnnotations #-}
+#if !defined(__HLINT__)
+{-# LANGUAGE StandaloneDeriving #-}
+#endif
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE TypeOperators #-}
+{-# LANGUAGE UndecidableInstances #-}
+
+module DependentLiterals.Bounds
+         ( -- * Bounds Checks
+
+           -- ** Error Messages
+           OutOfRangeMsg
+
+           -- ** Error Message Utilities
+         , ShowTypedNum, ShowRange
+
+           -- ** Error Constraints
+         , OutOfRangeErr
+
+           -- ** Inequality Assertions
+         , CheckLessThanMaxBound, CheckAtLeastMinBound, AssertEq, AssertNotApart
+
+           -- * Implementation Details
+         , ShowNum, AssertNotApart_, Eql, FailedToProveEq
+         ) where
+
+import Data.Kind (Constraint, Type)
+import GHC.TypeLits (TypeError, ErrorMessage(..))
+
+import Kinds.Integer (pattern Pos, pattern Neg)
+import Kinds.Num (type (-), type (>=?), type (<), type (>=), Cmp)
+import qualified Kinds.Integer as K (Integer)
+
+type family ShowNum (n :: K.Integer) where
+  ShowNum ('Pos n) = 'ShowType n
+  ShowNum ('Neg n) = 'Text "-" ':<>: 'ShowType n
+
+type ShowTypedNum a n = ShowNum n ':<>: 'Text " :: " ':<>: 'ShowType a
+
+type ShowRange min maxp1 =
+  'Text "(" ':<>: ShowNum min ':<>: 'Text ".." ':<>:
+  ShowNum (maxp1 - 'Pos 1) ':<>: 'Text ")"
+
+type OutOfRangeMsg min maxp1 a n =
+  'Text "Literal out of range " ':<>: ShowRange min maxp1 ':<>: 'Text ":" ':$$:
+  'Text "  " ':<>: ShowTypedNum a n
+
+class OutOfRangeErr (min :: K.Integer) (maxp1 :: K.Integer) (a :: Type) (n :: K.Integer)
+instance TypeError (OutOfRangeMsg min maxp1 a n) => OutOfRangeErr min maxp1 a n
+
+type family Eql a b :: Bool where
+  Eql a a = 'True
+  Eql a b = 'False
+
+class a ~ b => AssertEq (c :: Constraint) a b
+instance AssertEq c a a
+
+-- | If you tried to prove a constraint and failed, and want to issue a custom
+-- error message for it explicitly, write something like this.
+--
+-- Given "class _c => FailedToProveC (err :: Constraint) ...",
+-- "FailedToProveC (TypeError ...)" is a constraint that pretends to prove @c@
+-- but instead throws a type error.
+class a ~ b => FailedToProveEq (err :: Constraint) a b
+
+class a ~ b => AssertNotApart_ (msg :: ErrorMessage) eq a b
+instance a ~ b => AssertNotApart_ msg 'True a b
+instance FailedToProveEq (TypeError msg) a b => AssertNotApart_ msg 'False a b
+
+type AssertNotApart msg a b = AssertNotApart_ msg (Eql a b) a b
+
+class (n < maxp1)
+   => CheckLessThanMaxBound
+        (msg :: ErrorMessage)
+        (maxp1 :: K.Integer)
+        (a :: Type)
+        (n :: K.Integer)
+instance AssertNotApart msg (Cmp n maxp1) 'LT
+      => CheckLessThanMaxBound msg maxp1 a n
+
+class (n >= min)
+   => CheckAtLeastMinBound
+        (msg :: ErrorMessage)
+        (min :: K.Integer)
+        (a :: Type)
+        (n :: K.Integer)
+instance AssertNotApart msg (n >=? min) 'True
+      => CheckAtLeastMinBound msg min a n
diff --git a/src/DependentLiterals/Int.hs b/src/DependentLiterals/Int.hs
new file mode 100644
--- /dev/null
+++ b/src/DependentLiterals/Int.hs
@@ -0,0 +1,433 @@
+-- Copyright 2020-2021 Google LLC
+--
+-- Licensed under the Apache License, Version 2.0 (the "License");
+-- you may not use this file except in compliance with the License.
+-- You may obtain a copy of the License at
+--
+--      http://www.apache.org/licenses/LICENSE-2.0
+--
+-- Unless required by applicable law or agreed to in writing, software
+-- distributed under the License is distributed on an "AS IS" BASIS,
+-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+-- See the License for the specific language governing permissions and
+-- limitations under the License.
+
+{-# LANGUAGE AllowAmbiguousTypes #-}
+{-# LANGUAGE ConstraintKinds #-}
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE DerivingVia #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE InstanceSigs #-}
+{-# LANGUAGE KindSignatures #-}
+{-# LANGUAGE MagicHash #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE PatternSynonyms #-}
+{-# LANGUAGE PolyKinds #-}
+{-# LANGUAGE QuantifiedConstraints #-}
+{-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE RoleAnnotations #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeApplications #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE TypeOperators #-}
+{-# LANGUAGE UndecidableInstances #-}
+{-# LANGUAGE UndecidableSuperClasses #-}
+
+-- We hid all uses of this from HLint
+#if !defined(__HLINT__)
+{-# LANGUAGE StandaloneDeriving #-}
+#endif
+
+-- | The library component of "DependentLiterals.Plugin".
+--
+-- This provides a class for dependent numeric literal functionality, the entry
+-- points used by the plugin for literals and patterns, and a few ways of
+-- defining instances with less unsafe-ty.
+
+module DependentLiterals.Int
+         ( -- * Dependent Literals
+           HasIntLiterals(..), valueOf
+
+           -- ** Convenience Aliases
+         , HasBasicLiterals, AllowsIntLiteral, IntLiteral
+
+           -- ** Safer Implementations
+         , StockLit(..)
+         , SNum(..), Satisfying(..), SNumLit(..)
+         , type (-#), CMaybe(..)
+
+           -- ** Plugin Entry Points
+         , lit#, match#
+
+           -- * Implementation Details
+         , NoAssertion
+         ) where
+
+import Data.Functor.Const (Const(..))
+import Data.Functor.Identity (Identity(..))
+import Data.Int (Int8, Int16, Int32, Int64)
+import Data.Kind (Constraint, Type)
+import Data.Proxy (Proxy(..))
+import Data.Ratio (Ratio)
+import Data.Word (Word8, Word16, Word32, Word64)
+import Data.Semigroup (Sum(..), Product(..), Min(..), Max(..))
+import Data.Type.Equality ((:~:)(..))
+import Foreign.C.Types
+         ( CChar, CSChar, CUChar, CWchar
+         , CShort, CUShort, CInt, CUInt, CLong, CULong, CLLong, CULLong
+         , CPtrdiff, CSize, CSigAtomic, CBool
+         , CIntPtr, CUIntPtr, CIntMax, CUIntMax
+         , CClock, CTime, CUSeconds, CSUSeconds
+         )
+import GHC.TypeLits (TypeError, ErrorMessage(..))
+import GHC.TypeNats (Nat)
+import Numeric.Natural (Natural)
+import Unsafe.Coerce (unsafeCoerce)
+
+import Data.Tagged (Tagged(..))
+import Data.SInt (SInt(SI#, unSInt))
+import Data.SNumber (SafeSNumber, SNumber(N#), sameSNumber, unsafeMkSNumber)
+import Kinds.Integer (type (-#), KnownInteger(..), pattern Pos)
+import Kinds.Num (type (>=), type (<), Cmp, ToInteger)
+import qualified Kinds.Integer as K (Integer)
+import Data.Fin.Int (Fin, finToInt, unsafeFin)
+
+import DependentLiterals.Bounds
+         ( CheckAtLeastMinBound, CheckLessThanMaxBound
+         , AssertEq, OutOfRangeMsg, ShowTypedNum
+         )
+
+
+-- | A GADT containing some @t x@ along with a @c x@ instance.
+data Satisfying c t = forall x. c x => Satisfying (t x)
+
+-- | 'Maybe' on 'Constraint's.
+data CMaybe c = c => CJust | CNothing
+
+-- | A user-facing dependent numeric typeclass.
+--
+-- This gives an isomorphism between @a@ and @exists n. SNumber (SNumRepr a) n@
+-- given that @SNumConstraint a n@ holds.
+--
+-- To get instances of 'HasIntLiterals' without interacting with the unsafe
+-- parts of the library, implement this class and lift it to 'HasIntLiterals'
+-- with @deriving HasIntLiterals via SNumLit MyAssertionClass MyType@.
+class SNum a where
+  -- | The underlying numerical representation type.
+  type SNumRepr a :: Type
+
+  -- | The constraint on literal values to validate/refine @a@.
+  type SNumConstraint a :: K.Integer -> Constraint
+
+  -- | Conversion from 'SNumber' with a proof of 'SNumConstraint' into @a@.
+  --
+  -- Used for interpreting integral literals.
+  fromSNum :: Satisfying (SNumConstraint a) (SNumber (SNumRepr a)) -> a
+
+  -- | Conversion from @a@ into 'SNumber' with a proof of 'SNumConstraint.'
+  --
+  -- Used for providing proofs on successful pattern matches.
+  intoSNum :: a -> Satisfying (SNumConstraint a) (SNumber (SNumRepr a))
+
+instance SNum (SInt n) where
+  type SNumRepr (SInt n) = Int
+#if !defined(__HLINT__)
+  type SNumConstraint (SInt n) = (~) ('Pos n)
+#endif
+  fromSNum (Satisfying (N# x)) = SI# x
+  intoSNum x = Satisfying (N# @('Pos n) (unSInt x))
+
+instance SNum (SNumber a n) where
+  type SNumRepr (SNumber a n) = a
+#if !defined(__HLINT__)
+  type SNumConstraint (SNumber a n) = (~) n
+#endif
+  fromSNum (Satisfying x) = x
+  intoSNum = Satisfying
+
+class (Cmp n ('Pos m) ~ 'LT, n >= 'Pos 0)
+   => FinInBounds (m :: Nat) (n :: K.Integer)
+instance (Cmp n ('Pos m) ~ 'LT, n >= 'Pos 0) => FinInBounds m n
+
+instance SNum (Fin n) where
+  type SNumRepr (Fin n) = Int
+  type SNumConstraint (Fin n) = FinInBounds n
+  fromSNum (Satisfying (N# x)) = unsafeFin x
+  intoSNum x = unsafeCoerce (Satisfying @NoConstraint (N# (finToInt x)))
+
+-- | The main class providing dependent-literals functionality.
+--
+-- Instances of this can have integral literals and numeric patterns with
+-- @-fplugin="DependentLiterals.Plugin"@.
+--
+-- This class exposes the internal unsafe machinery of the library; a safer and
+-- less error-prone way to get instances for it is via 'SNum' or 'StockLit'.
+class HasIntLiterals a where
+  -- | Constraint for representational validity of a literal: this is meant to
+  -- prevent overflowed literals from being wrapped incorrectly in 'N#'.  This
+  -- is required both for expressions and for patterns.
+  --
+  -- Safety contract: 'unsafeFromInteger' and 'unsafeMatchInteger' must not
+  -- construct illegal @SNumber n@ values when called with @Tagged \@n n@; they
+  -- may use 'ReprAssertion' to restrict the values they can receive.
+  type ReprAssertion a :: Type -> K.Integer -> Constraint
+
+  -- | @LitConstraint a n@ constrains or refines @a@ given the literal value.
+  --
+  -- This is what's proven about the integer value and type by matching on a
+  -- numeric pattern; for example, in the case of @SInt n@, @LitConstraint a m@
+  -- is @m ~ n@, so that matching numeric 'SInt' patterns introduces equality
+  -- proofs for the type parameter.
+  type LitConstraint a :: K.Integer -> Constraint
+
+  -- | Like 'LitConstraint' but with pretty error messages.
+  --
+  -- This is used on integral literals to provide custom error messages for
+  -- failed constraints.
+  type LitAssertion a :: Type -> K.Integer -> Constraint
+
+  -- | Runtime conversion from 'Integer' to the appropriate type.
+  --
+  -- Unsafe in that it trusts that the 'Integer' you give it is the same as the
+  -- type-level one.
+  unsafeFromInteger
+    :: forall n b
+     . (LitAssertion a b n, ReprAssertion a b n)
+    => Proxy b -> Tagged n Integer -> a
+
+  -- | Runtime pattern match implementation.
+  --
+  -- Unsafe in that it trusts that the 'Integer' you give it is the same as the
+  -- type-level one.
+  unsafeMatchInteger
+    :: forall n b
+     . ReprAssertion a b n
+    => Proxy b -> Tagged n Integer -> a -> CMaybe (LitConstraint a n)
+
+-- | A constraint alias that asserts you can use any integral literal.
+--
+-- This can be useful in polymorphic contexts when you don't want to list out
+-- constraints for every literal value you need, and are willing to accept that
+-- some types with stronger compile-time validation will be excluded.
+type HasBasicLiterals a =
+  ( HasIntLiterals a
+  , LitAssertion a ~ NoAssertion
+  , ReprAssertion a ~ NoAssertion
+  )
+
+-- | A constraint alias showing that the particular value @n@ is valid for @a@.
+--
+-- With this in context along with @'HasIntLiterals' a@, you can use an
+-- integral literal value @n@ at type @a@.  See also 'IntLiteral'.
+type AllowsIntLiteral n a =
+  ( LitAssertion a a (ToInteger n)
+  , ReprAssertion a a (ToInteger n)
+  )
+
+-- | A convenient form of 'IntLiteral' when only one value is needed.
+--
+-- This is a constraint tuple, so using this multiple times in a signature
+-- creates a bit of constraint pollution; for tidier signatures, use one
+-- 'HasIntLiterals' and several 'AllowsIntLiteral's.
+type IntLiteral n a = (HasIntLiterals a, AllowsIntLiteral n a)
+
+-- | The unsafe entry point used by "DependentLiterals.Plugin" for literals.
+--
+-- This is unsafe to use explicitly, since it implicitly trusts that the given
+-- 'Integer' is equal to the type-level integer.  The plugin guarantees this
+-- itself when generating calls, so its uses are safe.
+lit#
+  :: forall n a
+   . (HasIntLiterals a, ReprAssertion a a n, LitAssertion a a n)
+  => (Num a => a) -> Integer -> a
+lit# _ = unsafeFromInteger (Proxy @a) . Tagged @n
+
+-- | The unsafe entry point used by "DependentLiterals.Plugin" for patterns.
+--
+-- This is unsafe to use explicitly, since it implicitly trusts that the given
+-- 'Integer' is equal to the type-level integer.  The plugin guarantees this
+-- itself when generating calls, so its uses are safe.
+match#
+  :: forall n a
+   . (HasIntLiterals a, ReprAssertion a a n)
+  => (Num a => a) -> Integer -> a -> CMaybe (LitConstraint a n)
+match# _ = unsafeMatchInteger (Proxy @a) . Tagged @n
+
+-- | 'valueOf' specialized to 'Integer'.
+valueOf' :: forall n a. (IntLiteral n a, KnownInteger n) => a
+valueOf' = unsafeFromInteger (Proxy @a) (Tagged @n $ toInteger $ integerVal @n)
+
+-- | Get the value of a type-level number at runtime, as if it were a literal.
+--
+-- That is, when DependentLiterals is enabled, @42@ and @valueOf \@42@ are the
+-- same thing.  (When it's not enabled, @42@ is just @fromInteger 42@).
+valueOf
+  :: forall n a
+   . (IntLiteral (ToInteger n) a, KnownInteger (ToInteger n))
+  => a
+valueOf = valueOf' @(ToInteger n)
+
+-- | A newtype carrying a 'HasIntLiterals' instance for use with @DerivingVia@.
+newtype SNumLit (c :: Type -> K.Integer -> Constraint) a = SNumLit a
+
+class SNumConstraint a n => SNumLitAssertion c a b n
+#if !defined(__HLINT__)
+instance (c b n, cc ~ SNumConstraint a, forall m. c b m => cc m)
+      => SNumLitAssertion c a b n
+#endif
+
+class SafeSNumber repr n => SNumReprAssertion repr b n
+instance SafeSNumber repr n => SNumReprAssertion repr b n
+
+instance (Eq (SNumRepr a), Num (SNumRepr a), SNum a)
+      => HasIntLiterals (SNumLit c a) where
+  type ReprAssertion (SNumLit c a) = SNumReprAssertion (SNumRepr a)
+  type LitAssertion (SNumLit c a) = SNumLitAssertion c a
+  type LitConstraint (SNumLit c a) = SNumConstraint a
+
+  unsafeFromInteger (_ :: Proxy b) (Tagged n :: Tagged n Integer) =
+    SNumLit $ fromSNum $ Satisfying (unsafeMkSNumber @n (fromInteger n))
+
+  unsafeMatchInteger (_ :: Proxy b) (Tagged n :: Tagged n Integer) (SNumLit a) =
+    case intoSNum a of
+      Satisfying m ->
+        case sameSNumber (unsafeMkSNumber @n (fromInteger n)) m of
+          Just Refl -> CJust
+          Nothing   -> CNothing
+
+
+-- | A type with a 'HasIntLiterals' instance that just behaves like 'Num'.
+--
+-- For use with @-XDerivingVia@.  This calls through to the 'fromIntegral' of
+-- the underlying 'Num' instance for the final conversion.  If the type in
+-- question has a 'Num' instance and it's acceptable for literals to overflow
+-- (or if the type is supported by -Woverflowed-literals), this is a good way
+-- to get an instance.
+--
+-- This is suitable for @DerivingVia@ and tends to work as a deriving clause,
+-- so:
+--
+-- @
+--     newtype MyType = MyType Int
+--       deriving Num
+--       deriving HasIntLiterals via StockLit Int
+-- @
+--
+-- Note in this case you could just as well say @deriving HasIntLiterals@ to
+-- get a @GeneralizedNewtypeDeriving@ instance that consumes Int literals and
+-- coerces them, but if you wrote a custom Num instance, @via FromIntegral _ _@
+-- will respect it.
+newtype StockLit a = StockLit a
+
+class NoConstraint (a :: k)
+instance NoConstraint a
+
+-- | The "assertion" used by basic integral literals, which is always solvable.
+class NoAssertion (a :: Type) (n :: K.Integer)
+instance NoAssertion a n
+
+instance (Eq a, Num a) => HasIntLiterals (StockLit a) where
+  type ReprAssertion (StockLit a) = NoAssertion
+  type LitConstraint (StockLit a) = NoConstraint
+  type LitAssertion (StockLit a) = NoAssertion
+
+  unsafeFromInteger _ (Tagged n) = StockLit (fromInteger n)
+
+  unsafeMatchInteger _ (Tagged n) (StockLit a) = if fromInteger n == a
+    then CJust
+    else CNothing
+
+class n ~ m => SIntLitAssertion (m :: K.Integer) (a :: Type) (n :: K.Integer)
+instance AssertEq
+           (TypeError
+             ('Text "SInt literal value does not match " ':<>:
+              'Text "expected type index:" ':$$:
+              'Text "  " ':<>: ShowTypedNum a n))
+           n
+           m
+      => SIntLitAssertion m a n
+
+class (n >= 'Pos 0, n < 'Pos m) => FinLitAssertion m a n
+instance ( CheckLessThanMaxBound
+             (OutOfRangeMsg ('Pos 0) ('Pos m) a n)
+             ('Pos m)
+             a
+             n
+         , CheckAtLeastMinBound
+             (OutOfRangeMsg ('Pos 0) ('Pos m) a n)
+             ('Pos 0)
+             a
+             n
+         )
+      => FinLitAssertion m a n
+
+-- HLint doesn't understand any of these because of DerivingVia :/
+#if !defined(__HLINT__)
+deriving via SNumLit (SIntLitAssertion ('Pos n)) (SInt n)
+  instance HasIntLiterals (SInt n)
+
+deriving via SNumLit (SIntLitAssertion n) (SNumber a n)
+  instance (Eq a, Num a) => HasIntLiterals (SNumber a n)
+
+deriving via SNumLit (FinLitAssertion n) (Fin n) instance HasIntLiterals (Fin n)
+
+deriving via StockLit Integer instance HasIntLiterals Integer
+deriving via StockLit Natural instance HasIntLiterals Natural
+deriving via StockLit (Ratio a) instance Integral a => HasIntLiterals (Ratio a)
+
+deriving via StockLit Int instance HasIntLiterals Int
+deriving via StockLit Int8 instance HasIntLiterals Int8
+deriving via StockLit Int16 instance HasIntLiterals Int16
+deriving via StockLit Int32 instance HasIntLiterals Int32
+deriving via StockLit Int64 instance HasIntLiterals Int64
+
+deriving via StockLit Word instance HasIntLiterals Word
+deriving via StockLit Word8 instance HasIntLiterals Word8
+deriving via StockLit Word16 instance HasIntLiterals Word16
+deriving via StockLit Word32 instance HasIntLiterals Word32
+deriving via StockLit Word64 instance HasIntLiterals Word64
+
+deriving via StockLit Float instance HasIntLiterals Float
+deriving via StockLit Double instance HasIntLiterals Double
+
+deriving via StockLit (Sum a)
+  instance (Eq a, Num a) => HasIntLiterals (Sum a)
+deriving via StockLit (Product a)
+  instance (Eq a, Num a) => HasIntLiterals (Product a)
+deriving via StockLit (Min a)
+  instance (Eq a, Num a) => HasIntLiterals (Min a)
+deriving via StockLit (Max a)
+  instance (Eq a, Num a) => HasIntLiterals (Max a)
+deriving via StockLit (Const a b)
+  instance (Eq a, Num a) => HasIntLiterals (Const a b)
+deriving via StockLit (Identity a)
+  instance (Eq a, Num a) => HasIntLiterals (Identity a)
+
+deriving via StockLit CChar instance HasIntLiterals CChar
+deriving via StockLit CSChar instance HasIntLiterals CSChar
+deriving via StockLit CUChar instance HasIntLiterals CUChar
+deriving via StockLit CShort instance HasIntLiterals CShort
+deriving via StockLit CUShort instance HasIntLiterals CUShort
+deriving via StockLit CInt instance HasIntLiterals CInt
+deriving via StockLit CUInt instance HasIntLiterals CUInt
+deriving via StockLit CLong instance HasIntLiterals CLong
+deriving via StockLit CULong instance HasIntLiterals CULong
+deriving via StockLit CPtrdiff instance HasIntLiterals CPtrdiff
+deriving via StockLit CSize instance HasIntLiterals CSize
+deriving via StockLit CWchar instance HasIntLiterals CWchar
+deriving via StockLit CSigAtomic instance HasIntLiterals CSigAtomic
+deriving via StockLit CLLong instance HasIntLiterals CLLong
+deriving via StockLit CULLong instance HasIntLiterals CULLong
+deriving via StockLit CBool instance HasIntLiterals CBool
+deriving via StockLit CIntPtr instance HasIntLiterals CIntPtr
+deriving via StockLit CUIntPtr instance HasIntLiterals CUIntPtr
+deriving via StockLit CIntMax instance HasIntLiterals CIntMax
+deriving via StockLit CUIntMax instance HasIntLiterals CUIntMax
+deriving via StockLit CClock instance HasIntLiterals CClock
+deriving via StockLit CTime instance HasIntLiterals CTime
+deriving via StockLit CUSeconds instance HasIntLiterals CUSeconds
+deriving via StockLit CSUSeconds instance HasIntLiterals CSUSeconds
+#endif