2 files changed, 69 insertions, 59 deletions
diff --git a/nix/tag/default.nix b/nix/tag/default.nix
index 9c55e6263b39..0038404460b1 100644
--- a/nix/tag/default.nix
+++ b/nix/tag/default.nix
@@ -4,22 +4,24 @@ let
   # if so sets `isTag` to `true` and sets the name and value.
   # If not, sets `isTag` to `false` and sets `errmsg`.
   verifyTag = tag:
-    let cases = builtins.attrNames tag;
-        len = builtins.length cases;
+    let
+      cases = builtins.attrNames tag;
+      len = builtins.length cases;
     in
     if builtins.length cases == 1
-    then let name = builtins.head cases; in {
-      isTag = true;
-      name = name;
-      val = tag.${name};
-      errmsg = null;
-    }
+    then
+      let name = builtins.head cases; in {
+        isTag = true;
+        name = name;
+        val = tag.${name};
+        errmsg = null;
+      }
     else {
       isTag = false;
       errmsg =
-        ( "match: an instance of a sum is an attrset "
-        + "with exactly one element, yours had ${toString len}"
-        + ", namely: ${lib.generators.toPretty {} cases}" );
+        ("match: an instance of a sum is an attrset "
+          + "with exactly one element, yours had ${toString len}"
+          + ", namely: ${lib.generators.toPretty {} cases}");
       name = null;
       val = null;
     };
@@ -63,21 +65,22 @@ let
   #   ] 1
   #   => { smol = 1; }
   discrDef = defTag: fs: v:
-    let res = lib.findFirst
-                (t: t.val v)
-                null
-                (map assertIsTag fs);
+    let
+      res = lib.findFirst
+        (t: t.val v)
+        null
+        (map assertIsTag fs);
     in
-      if res == null
-      then { ${defTag} = v; }
-      else { ${res.name} = v; };
+    if res == null
+    then { ${defTag} = v; }
+    else { ${res.name} = v; };
 
   # Like `discrDef`, but fail if there is no match.
   discr = fs: v:
     let res = discrDef null fs v; in
-      assert lib.assertMsg (res != null)
-        "tag.discr: No predicate found that matches ${lib.generators.toPretty {} v}";
-      res;
+    assert lib.assertMsg (res != null)
+      "tag.discr: No predicate found that matches ${lib.generators.toPretty {} v}";
+    res;
 
   # The canonical pattern matching primitive.
   # A sum value is an attribute set with one element,
@@ -104,17 +107,17 @@ let
   match = sum: matcher:
     let cases = builtins.attrNames sum;
     in assert
-      let len = builtins.length cases; in
-        lib.assertMsg (len == 1)
-          ( "match: an instance of a sum is an attrset "
-          + "with exactly one element, yours had ${toString len}"
-          + ", namely: ${lib.generators.toPretty {} cases}" );
+    let len = builtins.length cases; in
+    lib.assertMsg (len == 1)
+      ("match: an instance of a sum is an attrset "
+        + "with exactly one element, yours had ${toString len}"
+        + ", namely: ${lib.generators.toPretty {} cases}");
     let case = builtins.head cases;
     in assert
-        lib.assertMsg (matcher ? ${case})
-        ( "match: \"${case}\" is not a valid case of this sum, "
+    lib.assertMsg (matcher ? ${case})
+      ("match: \"${case}\" is not a valid case of this sum, "
         + "the matcher accepts: ${lib.generators.toPretty {}
-            (builtins.attrNames matcher)}" );
+            (builtins.attrNames matcher)}");
     matcher.${case} sum.${case};
 
   # A `match` with the arguments flipped.
@@ -148,15 +151,16 @@ let
       ;
   };
 
-in {
-   inherit
-     verifyTag
-     tagName
-     tagValue
-     discr
-     discrDef
-     match
-     matchLam
-     tests
-     ;
+in
+{
+  inherit
+    verifyTag
+    tagName
+    tagValue
+    discr
+    discrDef
+    match
+    matchLam
+    tests
+    ;
 }
diff --git a/nix/tag/tests.nix b/nix/tag/tests.nix
index 8c9c73807472..bcc42c758a6c 100644
--- a/nix/tag/tests.nix
+++ b/nix/tag/tests.nix
@@ -17,7 +17,7 @@ let
         errmsg = null;
       })
     (assertEq "is not Tag"
-      (removeAttrs (verifyTag { foo = "bar"; baz = 42; }) ["errmsg"])
+      (removeAttrs (verifyTag { foo = "bar"; baz = 42; }) [ "errmsg" ])
       {
         isTag = false;
         name = null;
@@ -41,7 +41,8 @@ let
       (discr [
         { bool = lib.isBool; }
         { int = lib.isInt; }
-      ] true)
+      ]
+        true)
       { bool = true; })
     (assertEq "fallback to default"
       (discrDef "def" [
@@ -53,19 +54,24 @@ let
 
   match-test = it "can match things" [
     (assertEq "match example"
-      (let
-        success = { res = 42; };
-        failure = { err = "no answer"; };
-        matcher = {
-          res = i: i + 1;
-          err = _: 0;
-        };
-      in {
-        one = match success matcher;
-        two = match failure matcher;
+      (
+        let
+          success = { res = 42; };
+          failure = { err = "no answer"; };
+          matcher = {
+            res = i: i + 1;
+            err = _: 0;
+          };
+        in
+        {
+          one = match success matcher;
+          two = match failure matcher;
+        }
+      )
+      {
+        one = 43;
+        two = 0;
       })
-      { one = 43;
-        two = 0; })
     (assertEq "matchLam & pipe"
       (lib.pipe { foo = 42; } [
         (matchLam {
@@ -81,8 +87,8 @@ let
   ];
 
 in
-  runTestsuite "tag" [
-    isTag-test
-    discr-test
-    match-test
-  ]
+runTestsuite "tag" [
+  isTag-test
+  discr-test
+  match-test
+]