From 9f7e87e9356b8802e4bb13fc6555088468fd3d7f Mon Sep 17 00:00:00 2001
From: Felix Krause <contact@flyx.org>
Date: Sat, 8 Oct 2016 20:57:53 +0200
Subject: [PATCH] Ordered snippets with file system hierarchy

---
 doc/examples/quickstart.json                  |  43 -------
 doc/index.txt                                 |   5 +-
 doc/rstPreproc.nim                            | 119 +++++++++---------
 .../quickstart/01/code.nim}                   |   0
 .../quickstart/01/out.yaml}                   |   0
 doc/snippets/quickstart/01/title              |   1 +
 .../quickstart/02/code.nim}                   |   0
 .../quickstart/02/in.yaml}                    |   0
 doc/snippets/quickstart/02/title              |   1 +
 .../quickstart/03/code.nim}                   |   0
 .../quickstart/03/out.yaml}                   |   0
 doc/snippets/quickstart/03/title              |   1 +
 .../quickstart/04/code.nim}                   |   0
 .../quickstart/04/out.yaml}                   |   0
 doc/snippets/quickstart/04/title              |   1 +
 .../quickstart/05/code.nim}                   |   0
 .../quickstart/05/in.yaml}                    |   0
 doc/snippets/quickstart/05/title              |   1 +
 .../quickstart/06/code.nim}                   |   0
 .../quickstart/06/out.yaml}                   |   0
 doc/snippets/quickstart/06/title              |   1 +
 .../quickstart/07/code.nim}                   |   0
 .../quickstart/07/out.yaml}                   |   0
 doc/snippets/quickstart/07/title              |   1 +
 .../quickstart/08/code.nim}                   |   0
 .../quickstart/08/in.yaml}                    |   0
 doc/snippets/quickstart/08/title              |   1 +
 .../quickstart/09/01/code.nim}                |   0
 .../quickstart/09/01/in.yaml}                 |   0
 doc/snippets/quickstart/09/01/title           |   1 +
 .../quickstart/09/02/code.nim}                |   0
 .../quickstart/09/02/in.yaml}                 |   0
 doc/snippets/quickstart/09/02/title           |   1 +
 doc/snippets/quickstart/09/title              |   1 +
 doc/snippets/quickstart/title                 |   1 +
 yaml/serialization.nim                        |  44 ++++++-
 yaml/taglib.nim                               |  26 ----
 37 files changed, 116 insertions(+), 133 deletions(-)
 delete mode 100644 doc/examples/quickstart.json
 rename doc/{examples/dump-yaml.nim => snippets/quickstart/01/code.nim} (100%)
 rename doc/{examples/dump-yaml.out.yaml => snippets/quickstart/01/out.yaml} (100%)
 create mode 100644 doc/snippets/quickstart/01/title
 rename doc/{examples/load-yaml.nim => snippets/quickstart/02/code.nim} (100%)
 rename doc/{examples/load-yaml.in.yaml => snippets/quickstart/02/in.yaml} (100%)
 create mode 100644 doc/snippets/quickstart/02/title
 rename doc/{examples/outputstyle.nim => snippets/quickstart/03/code.nim} (100%)
 rename doc/{examples/outputstyle.out.yaml => snippets/quickstart/03/out.yaml} (100%)
 create mode 100644 doc/snippets/quickstart/03/title
 rename doc/{examples/dump-reftypes.nim => snippets/quickstart/04/code.nim} (100%)
 rename doc/{examples/dump-reftypes.out.yaml => snippets/quickstart/04/out.yaml} (100%)
 create mode 100644 doc/snippets/quickstart/04/title
 rename doc/{examples/load-reftypes.nim => snippets/quickstart/05/code.nim} (100%)
 rename doc/{examples/load-reftypes.in.yaml => snippets/quickstart/05/in.yaml} (100%)
 create mode 100644 doc/snippets/quickstart/05/title
 rename doc/{examples/customtag.nim => snippets/quickstart/06/code.nim} (100%)
 rename doc/{examples/customtag.out.yaml => snippets/quickstart/06/out.yaml} (100%)
 create mode 100644 doc/snippets/quickstart/06/title
 rename doc/{examples/dump-json.nim => snippets/quickstart/07/code.nim} (100%)
 rename doc/{examples/dump-json.out.yaml => snippets/quickstart/07/out.yaml} (100%)
 create mode 100644 doc/snippets/quickstart/07/title
 rename doc/{examples/load-json.nim => snippets/quickstart/08/code.nim} (100%)
 rename doc/{examples/load-json.in.yaml => snippets/quickstart/08/in.yaml} (100%)
 create mode 100644 doc/snippets/quickstart/08/title
 rename doc/{examples/implicit-variant.nim => snippets/quickstart/09/01/code.nim} (100%)
 rename doc/{examples/implicit-variant.in.yaml => snippets/quickstart/09/01/in.yaml} (100%)
 create mode 100644 doc/snippets/quickstart/09/01/title
 rename doc/{examples/sequential-api.nim => snippets/quickstart/09/02/code.nim} (100%)
 rename doc/{examples/sequential-api.in.yaml => snippets/quickstart/09/02/in.yaml} (100%)
 create mode 100644 doc/snippets/quickstart/09/02/title
 create mode 100644 doc/snippets/quickstart/09/title
 create mode 100644 doc/snippets/quickstart/title

diff --git a/doc/examples/quickstart.json b/doc/examples/quickstart.json
deleted file mode 100644
index b8efe1c..0000000
--- a/doc/examples/quickstart.json
+++ /dev/null
@@ -1,43 +0,0 @@
-{
-  "Dumping Nim objects as YAML": [
-    "dump-yaml", "out"
-  ],
-
-  "Loading Nim objects from YAML": [
-    "load-yaml", "in"
-  ],
-
-  "Customizing output style" : [
-    "outputstyle", "out"
-  ],
-
-  "Dumping reference types and cyclic structures": [
-    "dump-reftypes", "out"
-  ],
-
-  "Loading reference types and cyclic structures": [
-    "load-reftypes", "in"
-  ],
-
-  "Defining a custom tag uri for a type": [
-    "customtag", "out"
-  ],
-
-  "Dumping Nim objects as JSON": [
-    "dump-json", "out"
-  ],
-
-  "Loading Nim objects from JSON": [
-    "load-json", "in"
-  ],
-
-  "Processing a Sequence of Heterogeneous Items": {
-    "… With variant objects": [
-      "implicit-variant", "in"
-    ],
-
-    "… With the Sequential API": [
-      "sequential-api", "in"
-    ]
-  }
-}
\ No newline at end of file
diff --git a/doc/index.txt b/doc/index.txt
index 3bd71cd..d1a7498 100644
--- a/doc/index.txt
+++ b/doc/index.txt
@@ -16,7 +16,4 @@ install it with `Nimble <https://github.com/nim-lang/nimble>`_:
 .. code-block:: bash
   nimble install yaml
 
-Quickstart
-==========
-
-%examples/quickstart.json%/
\ No newline at end of file
+%quickstart%0
\ No newline at end of file
diff --git a/doc/rstPreproc.nim b/doc/rstPreproc.nim
index 6b92460..22522eb 100644
--- a/doc/rstPreproc.nim
+++ b/doc/rstPreproc.nim
@@ -1,9 +1,10 @@
 ## This is a tool for preprocessing rst files. Lines starting with ``%`` will
-## get substituted by nicely layouted included nim and yaml code.
+## get substituted by nicely layouted nim and yaml code included from file in
+## the snippets tree.
 ##
-## The syntax of substituted lines is ``'%' jsonfile '%' jsonpath``. *jsonfile*
-## shall be the path to a JSON file. *jsonpath* shall be a path to some node in
-## that JSON file.
+## The syntax of substituted lines is ``'%' path '%' level``. *path* shall be
+## a path relative to the *snippets* directory. *level* shall be the level depth
+## of the first title that should be produced.
 ##
 ## Usage:
 ##
@@ -11,8 +12,12 @@
 ##
 ## *path* is the output path. If omitted, it will be equal to infile with its
 ## suffix substituted by ``.rst``. *infile* is the source rst file.
+##
+## The reason for this complex approach is to have all snippets used in the docs
+## available as source files for automatic testing. This way, we can make sure
+## that the code in the docs actually works.
 
-import parseopt2, json, streams, tables, strutils, os
+import parseopt2, streams, tables, strutils, os
 
 var
   infile = ""
@@ -57,71 +62,73 @@ var tmpOut = newFileStream(path, fmWrite)
 proc append(s: string) =
   tmpOut.writeLine(s)
 
-proc gotoPath(root: JsonNode, path: string): JsonNode =
-  doAssert path[0] == '/'
-  if path.len == 1: return root
-  doAssert root.kind == JObject
-  for i in 1..<path.len:
-    if path[i] == '/':
-      return gotoPath(root.getFields()[path[1..<i]], path[i+1 .. ^1])
-  return root.getFields()[path[1..^1]]
+const headingChars = ['=', '-', '`', ':', '\'']
 
-const headingChars = ['-', '`', ':', '\'']
-
-proc outputExamples(node: JsonNode, prefix: string, level: int = 0) =
-  case node.kind
-  of JObject:
-    for key, value in node.getFields():
-      append(key)
+proc outputExamples(curPath: string, level: int = 0) =
+  let titlePath = curPath / "title"
+  if fileExists(titlePath):
+    let titleFile = open(titlePath, fmRead)
+    defer: titleFile.close()
+    var title = ""
+    if titleFile.readLine(title):
       let headingChar = if level >= headingChars.len: headingChars[^1] else:
           headingChars[level]
-      append(repeat(headingChar, key.len) & '\l')
-      outputExamples(value, prefix, level + 1)
-  of JArray:
-    let elems = node.getElems()
-    case elems.len
-    of 2:
-      append(".. raw:: html")
-      append("  <table class=\"quickstart-example\"><thead><tr><th>code.nim</th>")
-      append("  <th>" & elems[1].getStr() &
-             ".yaml</th></tr></thead><tbody><tr><td>\n")
-      append(".. code:: nim")
-      append("   :file: " & prefix & elems[0].getStr() & ".nim\n")
-      append(".. raw:: html")
-      append("  </td>\n  <td>\n")
-      append(".. code:: yaml")
-      append("   :file: " & prefix & elems[0].getStr() & '.' &
-             elems[1].getStr() & ".yaml\n")
-      append(".. raw:: html")
-      append("  </td></tr></tbody></table>\n")
-    else:
-      echo "Unexpected number of elements in array: ", elems.len
-      quit 1
+      append(title)
+      append(repeat(headingChar, title.len) & '\l')
+
+  # process content files under this directory
+
+  var codeFiles = newSeq[string]()
+  for kind, filePath in walkDir(curPath, true):
+    if kind == pcFile:
+      if filePath != "title": codeFiles.add(filePath)
+  case codeFiles.len
+  of 0: discard
+  of 1:
+    let (nullPath, name, extension) = codeFiles[0].splitFile()
+    append(".. code:: " & extension[1..^1])
+    append("   :file: " & (curPath / codeFiles[0]) & '\l')
+  of 2:
+    append(".. raw:: html")
+    append("  <table class=\"quickstart-example\"><thead><tr>")
+    for codeFile in codeFiles:
+      append("    <th>" & codeFile & "</th>")
+    append("  </th></tr></thead><tbody><tr><td>\n")
+
+    var first = true
+    for codeFile in codeFiles:
+      if first: first = false
+      else: append(".. raw:: html\n  </td>\n  <td>\n")
+      let (nullPath, name, extension) = codeFile.splitFile()
+      append(".. code:: " & extension[1..^1])
+      append("   :file: " & (curPath / codeFile) & '\l')
+
+    append(".. raw:: html")
+    append("  </td></tr></tbody></table>\n")
   else:
-    echo "Unexpected node kind: ", node.kind
-    quit 1
+    echo "Unexpected number of files in ", curPath, ": ", codeFiles.len
+
+  # process child directories
+
+  for kind, dirPath in walkDir(curPath):
+    if kind == pcDir:
+      outputExamples(dirPath, level + 1)
 
 var lineNum = 0
 for line in infile.lines():
   if line.len > 0 and line[0] == '%':
     var
-      jsonFile: string = nil
-      jsonPath: string = nil
+      srcPath: string = nil
+      level = 0
     for i in 1..<line.len:
       if line[i] == '%':
-        jsonFile = line[1 .. i - 1]
-        jsonPath = line[i + 1 .. ^1]
+        srcPath = line[1 .. i - 1]
+        level = parseInt(line[i + 1 .. ^1])
         break
-    if isNil(jsonFile):
+    if isNil(srcPath):
       echo "Second % missing in line " & $lineNum & "! content:\n"
       echo line
       quit 1
-    let root = parseFile(jsonFile)
-    var prefix = ""
-    for i in countdown(jsonFile.len - 1, 0):
-      if jsonFile[i] == '/':
-        prefix = jsonFile[0..i]
-        break
-    outputExamples(root.gotoPath(jsonPath), prefix)
+    outputExamples("snippets" / srcPath, level)
   else:
     append(line)
diff --git a/doc/examples/dump-yaml.nim b/doc/snippets/quickstart/01/code.nim
similarity index 100%
rename from doc/examples/dump-yaml.nim
rename to doc/snippets/quickstart/01/code.nim
diff --git a/doc/examples/dump-yaml.out.yaml b/doc/snippets/quickstart/01/out.yaml
similarity index 100%
rename from doc/examples/dump-yaml.out.yaml
rename to doc/snippets/quickstart/01/out.yaml
diff --git a/doc/snippets/quickstart/01/title b/doc/snippets/quickstart/01/title
new file mode 100644
index 0000000..fd45668
--- /dev/null
+++ b/doc/snippets/quickstart/01/title
@@ -0,0 +1 @@
+Dumping Nim objects as YAML
diff --git a/doc/examples/load-yaml.nim b/doc/snippets/quickstart/02/code.nim
similarity index 100%
rename from doc/examples/load-yaml.nim
rename to doc/snippets/quickstart/02/code.nim
diff --git a/doc/examples/load-yaml.in.yaml b/doc/snippets/quickstart/02/in.yaml
similarity index 100%
rename from doc/examples/load-yaml.in.yaml
rename to doc/snippets/quickstart/02/in.yaml
diff --git a/doc/snippets/quickstart/02/title b/doc/snippets/quickstart/02/title
new file mode 100644
index 0000000..96a5007
--- /dev/null
+++ b/doc/snippets/quickstart/02/title
@@ -0,0 +1 @@
+Loading Nim objects from YAML
diff --git a/doc/examples/outputstyle.nim b/doc/snippets/quickstart/03/code.nim
similarity index 100%
rename from doc/examples/outputstyle.nim
rename to doc/snippets/quickstart/03/code.nim
diff --git a/doc/examples/outputstyle.out.yaml b/doc/snippets/quickstart/03/out.yaml
similarity index 100%
rename from doc/examples/outputstyle.out.yaml
rename to doc/snippets/quickstart/03/out.yaml
diff --git a/doc/snippets/quickstart/03/title b/doc/snippets/quickstart/03/title
new file mode 100644
index 0000000..944d448
--- /dev/null
+++ b/doc/snippets/quickstart/03/title
@@ -0,0 +1 @@
+Customizing output style
diff --git a/doc/examples/dump-reftypes.nim b/doc/snippets/quickstart/04/code.nim
similarity index 100%
rename from doc/examples/dump-reftypes.nim
rename to doc/snippets/quickstart/04/code.nim
diff --git a/doc/examples/dump-reftypes.out.yaml b/doc/snippets/quickstart/04/out.yaml
similarity index 100%
rename from doc/examples/dump-reftypes.out.yaml
rename to doc/snippets/quickstart/04/out.yaml
diff --git a/doc/snippets/quickstart/04/title b/doc/snippets/quickstart/04/title
new file mode 100644
index 0000000..4ffce07
--- /dev/null
+++ b/doc/snippets/quickstart/04/title
@@ -0,0 +1 @@
+Dumping reference types and cyclic structures
diff --git a/doc/examples/load-reftypes.nim b/doc/snippets/quickstart/05/code.nim
similarity index 100%
rename from doc/examples/load-reftypes.nim
rename to doc/snippets/quickstart/05/code.nim
diff --git a/doc/examples/load-reftypes.in.yaml b/doc/snippets/quickstart/05/in.yaml
similarity index 100%
rename from doc/examples/load-reftypes.in.yaml
rename to doc/snippets/quickstart/05/in.yaml
diff --git a/doc/snippets/quickstart/05/title b/doc/snippets/quickstart/05/title
new file mode 100644
index 0000000..225029d
--- /dev/null
+++ b/doc/snippets/quickstart/05/title
@@ -0,0 +1 @@
+Loading reference types and cyclic structures
diff --git a/doc/examples/customtag.nim b/doc/snippets/quickstart/06/code.nim
similarity index 100%
rename from doc/examples/customtag.nim
rename to doc/snippets/quickstart/06/code.nim
diff --git a/doc/examples/customtag.out.yaml b/doc/snippets/quickstart/06/out.yaml
similarity index 100%
rename from doc/examples/customtag.out.yaml
rename to doc/snippets/quickstart/06/out.yaml
diff --git a/doc/snippets/quickstart/06/title b/doc/snippets/quickstart/06/title
new file mode 100644
index 0000000..dda14d4
--- /dev/null
+++ b/doc/snippets/quickstart/06/title
@@ -0,0 +1 @@
+Defining a custom tag uri for a type
diff --git a/doc/examples/dump-json.nim b/doc/snippets/quickstart/07/code.nim
similarity index 100%
rename from doc/examples/dump-json.nim
rename to doc/snippets/quickstart/07/code.nim
diff --git a/doc/examples/dump-json.out.yaml b/doc/snippets/quickstart/07/out.yaml
similarity index 100%
rename from doc/examples/dump-json.out.yaml
rename to doc/snippets/quickstart/07/out.yaml
diff --git a/doc/snippets/quickstart/07/title b/doc/snippets/quickstart/07/title
new file mode 100644
index 0000000..21eb8cf
--- /dev/null
+++ b/doc/snippets/quickstart/07/title
@@ -0,0 +1 @@
+Dumping Nim objects as JSON
diff --git a/doc/examples/load-json.nim b/doc/snippets/quickstart/08/code.nim
similarity index 100%
rename from doc/examples/load-json.nim
rename to doc/snippets/quickstart/08/code.nim
diff --git a/doc/examples/load-json.in.yaml b/doc/snippets/quickstart/08/in.yaml
similarity index 100%
rename from doc/examples/load-json.in.yaml
rename to doc/snippets/quickstart/08/in.yaml
diff --git a/doc/snippets/quickstart/08/title b/doc/snippets/quickstart/08/title
new file mode 100644
index 0000000..5fb44c7
--- /dev/null
+++ b/doc/snippets/quickstart/08/title
@@ -0,0 +1 @@
+Loading Nim objects from JSON
diff --git a/doc/examples/implicit-variant.nim b/doc/snippets/quickstart/09/01/code.nim
similarity index 100%
rename from doc/examples/implicit-variant.nim
rename to doc/snippets/quickstart/09/01/code.nim
diff --git a/doc/examples/implicit-variant.in.yaml b/doc/snippets/quickstart/09/01/in.yaml
similarity index 100%
rename from doc/examples/implicit-variant.in.yaml
rename to doc/snippets/quickstart/09/01/in.yaml
diff --git a/doc/snippets/quickstart/09/01/title b/doc/snippets/quickstart/09/01/title
new file mode 100644
index 0000000..237f9a9
--- /dev/null
+++ b/doc/snippets/quickstart/09/01/title
@@ -0,0 +1 @@
+… With variant objects
diff --git a/doc/examples/sequential-api.nim b/doc/snippets/quickstart/09/02/code.nim
similarity index 100%
rename from doc/examples/sequential-api.nim
rename to doc/snippets/quickstart/09/02/code.nim
diff --git a/doc/examples/sequential-api.in.yaml b/doc/snippets/quickstart/09/02/in.yaml
similarity index 100%
rename from doc/examples/sequential-api.in.yaml
rename to doc/snippets/quickstart/09/02/in.yaml
diff --git a/doc/snippets/quickstart/09/02/title b/doc/snippets/quickstart/09/02/title
new file mode 100644
index 0000000..99176f2
--- /dev/null
+++ b/doc/snippets/quickstart/09/02/title
@@ -0,0 +1 @@
+… With the Sequential API
diff --git a/doc/snippets/quickstart/09/title b/doc/snippets/quickstart/09/title
new file mode 100644
index 0000000..d413d92
--- /dev/null
+++ b/doc/snippets/quickstart/09/title
@@ -0,0 +1 @@
+Processing a Sequence of Heterogeneous Items
diff --git a/doc/snippets/quickstart/title b/doc/snippets/quickstart/title
new file mode 100644
index 0000000..ddddbf8
--- /dev/null
+++ b/doc/snippets/quickstart/title
@@ -0,0 +1 @@
+Quickstart
diff --git a/yaml/serialization.nim b/yaml/serialization.nim
index 0f384cd..df95ac5 100644
--- a/yaml/serialization.nim
+++ b/yaml/serialization.nim
@@ -738,15 +738,20 @@ macro constructImplicitVariantObject(s, c, r, possibleTagIds: untyped,
   ))
   ifStmt.add(newNimNode(nnkElse).add(newNimNode(nnkTryStmt).add(
       newStmtList(raiseStmt), newNimNode(nnkExceptBranch).add(
-        newIdentNode("KeyError"), newStmtList(newCall("internalError",
-        newStrLitNode("Unexcpected KeyError")))
+        newNimNode(nnkDiscardStmt).add(newEmptyNode())
   ))))
   result = newStmtList(newCall("reset", r), ifStmt)
 
+let implicitVariantObjectMarker {.compileTime.} =
+    newIdentNode(":implicitVariantObject")
+
+macro isImplicitVariantObject(o: typed): untyped =
+  result = newCall("compiles", newCall(implicitVariantObjectMarker, o))
+
 proc constructChild*[T](s: var YamlStream, c: ConstructionContext,
                         result: var T) =
   let item = s.peek()
-  when compiles(implicitVariantObject(result)):
+  when isImplicitVariantObject(result):
     var possibleTagIds = newSeq[TagId]()
     case item.kind
     of yamlScalar:
@@ -915,7 +920,7 @@ proc representChild*[O](value: ref O, ts: TagStyle, c: SerializationContext) =
 
 proc representChild*[O](value: O, ts: TagStyle,
                         c: SerializationContext) =
-  when compiles(implicitVariantObject(value)):
+  when isImplicitVariantObject(value):
     # todo: this would probably be nicer if constructed with a macro
     var count = 0
     for name, field in fieldPairs(value):
@@ -1032,3 +1037,34 @@ proc dump*[K](value: K, tagStyle: TagStyle = tsRootOnly,
   try: result = present(events, serializationTagLibrary, options)
   except YamlStreamError:
     internalError("Unexpected exception: " & getCurrentException().repr)
+
+proc canBeImplicit(t: typedesc): bool {.compileTime.} =
+  let tDesc = getType(t)
+  if tDesc.kind != nnkObjectTy: return false
+  if tDesc[2].len != 1: return false
+  if tDesc[2][0].kind != nnkRecCase: return false
+  var foundEmptyBranch = false
+  for i in 1.. tDesc[2][0].len - 1:
+    case tDesc[2][0][i][1].len # branch contents
+    of 0:
+      if foundEmptyBranch: return false
+      else: foundEmptyBranch = true
+    of 1: discard
+    else: return false
+  return true
+
+macro setImplicitVariantObjectMarker(t: typedesc): untyped =
+  result = quote do:
+    proc `implicitVariantObjectMarker`*(unused: `t`) = discard
+
+template markAsImplicit*(t: typedesc): typed =
+  ## Mark a variant object type as implicit. This requires the type to consist
+  ## of nothing but a case expression and each branch of the case expression
+  ## containing exactly one field - with the exception that one branch may
+  ## contain zero fields.
+  when canBeImplicit(t):
+    # this will be checked by means of compiles(implicitVariantObject(...))
+    setImplicitVariantObjectMarker(t)
+  else:
+    {. fatal: "This type cannot be marked as implicit" .}
+
diff --git a/yaml/taglib.nim b/yaml/taglib.nim
index 5a2ddcc..25f99e8 100644
--- a/yaml/taglib.nim
+++ b/yaml/taglib.nim
@@ -253,32 +253,6 @@ template setTagUri*(t: typedesc, uri: string, idName: untyped): typed =
   proc yamlTag*(T: typedesc[t]): TagId {.inline, raises: [].} = idName
     ## autogenerated
 
-proc canBeImplicit(t: typedesc): bool {.compileTime.} =
-  let tDesc = getType(t)
-  if tDesc.kind != nnkObjectTy: return false
-  if tDesc[2].len != 1: return false
-  if tDesc[2][0].kind != nnkRecCase: return false
-  var foundEmptyBranch = false
-  for i in 1.. tDesc[2][0].len - 1:
-    case tDesc[2][0][i][1].len # branch contents
-    of 0:
-      if foundEmptyBranch: return false
-      else: foundEmptyBranch = true
-    of 1: discard
-    else: return false
-  return true
-
-template markAsImplicit*(t: typedesc): typed =
-  ## Mark a variant object type as implicit. This requires the type to consist
-  ## of nothing but a case expression and each branch of the case expression
-  ## containing exactly one field - with the exception that one branch may
-  ## contain zero fields.
-  when canBeImplicit(t):
-    # this will be checked by means of compiles(implicitVariantObject(...))
-    proc implicitVariantObject*(unused: t) = discard
-  else:
-    {. fatal: "This type cannot be marked as implicit" .}
-
 static:
   # standard YAML tags used by serialization
   registeredUris.add("!")