Nim regression test for canBeImplicit

config.nims

@@ -6,7 +6,7 @@ task build, "Compile the YAML module into a library":
 task test, "Run all tests":
   --r
   --verbosity:0
-  setCommand "c", "test/tests"
+  setCommand "c", "test/tnimregress"
 
 task lexerTests, "Run lexer tests":
   --r

test/tnimregress.nim

@@ -0,0 +1,46 @@
+import unittest, macros
+
+type
+  Person = object
+    name: string
+
+  ContainerKind = enum
+    ckString, ckInt, ckBool, ckPerson, ckNone
+
+  Container = object
+    case kind: ContainerKind
+    of ckString:
+      strVal: string
+    of ckInt:
+      intVal: int
+    of ckBool:
+      boolVal: bool
+    of ckPerson:
+      personVal: Person
+    of ckNone:
+      discard
+
+proc recListLen(n: NimNode): int {.compileTime.} =
+  if n.kind == nnkRecList: result = n.len
+  else: result = 1
+
+proc canBeImplicit(t: typedesc): string {.compileTime.} =
+  ## returns empty string if type can be implicit, else the reason why it can't
+  let tDesc = getType(t)
+  if tDesc.kind != nnkObjectTy: return "type is not an object"
+  if tDesc[2].len != 1 or tDesc[2][0].kind != nnkRecCase:
+    return "type doesn't exclusively contain record case"
+  var foundEmptyBranch = false
+  for i in 1.. tDesc[2][0].len - 1:
+    case tDesc[2][0][i][1].recListlen # branch contents
+    of 0:
+      if foundEmptyBranch: return "record case has more than one empty branch"
+      else: foundEmptyBranch = true
+    of 1: discard
+    else: return "record case contains more than one field"
+
+suite "Nim Regression Tests":
+  test "canBeImplicit":
+    const res = canBeImplicit(Container)
+    assert len(res) == 0, "unexpected error for canBeImplicit: " & res
+