fixed macros.getTypeImpl for a symbol of type tyGenericBody (#5788) (#5812)

* fixed macros.getTypeImpl for a symbol of type tyGenericBody
* added test case and commented test code

3 files changed, 55 insertions, 19 deletions

diff --git a/compiler/vmdeps.nim b/compiler/vmdeps.nim
index 8c7388643..b2b1ec92b 100644
--- a/compiler/vmdeps.nim
+++ b/compiler/vmdeps.nim
@@ -175,7 +175,12 @@ proc mapTypeToAstX(t: PType; info: TLineInfo;
           result.add mapTypeToAst(t.sons[i], info)
     else:
       result = mapTypeToAstX(t.lastSon, info, inst, allowRecursion)
-  of tyGenericBody, tyOrdinal:
+  of tyGenericBody:
+    if inst:
+      result = mapTypeToAstX(t.lastSon, info, inst, true)
+    else:
+      result = mapTypeToAst(t.lastSon, info)
+  of tyOrdinal:
     result = mapTypeToAst(t.lastSon, info)
   of tyDistinct:
     if inst:
diff --git a/tests/macros/tgettypeinst.nim b/tests/macros/tgettypeinst.nim
index 255eff949..f89aa5e0b 100644
--- a/tests/macros/tgettypeinst.nim
+++ b/tests/macros/tgettypeinst.nim
@@ -21,49 +21,67 @@ proc symToIdent(x: NimNode): NimNode =
       for c in x:
         result.add symToIdent(c)
 
+# check getTypeInst and getTypeImpl for given symbol x
 macro testX(x,inst0: typed; recurse: static[bool]; implX: stmt): typed =
+  # check that getTypeInst(x) equals inst0
   let inst = x.getTypeInst
-  let impl = x.getTypeImpl
-  let inst0r = inst0.symToIdent.treeRepr
   let instr = inst.symToIdent.treeRepr
-  #echo inst0r
+  let inst0r = inst0.symToIdent.treeRepr
   #echo instr
+  #echo inst0r
   doAssert(instr == inst0r)
+
+  # check that getTypeImpl(x) is correct
+  #  if implX is nil then compare to inst0
+  #  else we expect implX to be a type definition
+  #       and we extract the implementation from that
+  let impl = x.getTypeImpl
   var impl0 =
     if implX.kind == nnkNilLit: inst0
     else: implX[0][2]
-  let impl0r = impl0.symToIdent.treerepr
   let implr = impl.symToIdent.treerepr
-  #echo impl0r
+  let impl0r = impl0.symToIdent.treerepr
   #echo implr
+  #echo impl0r
   doAssert(implr == impl0r)
-  template echoString(s:string) = echo s.replace("\n","\n  ")
+
   result = newStmtList()
+  #template echoString(s: string) = echo s.replace("\n","\n  ")
   #result.add getAst(echoString("  " & inst0.repr))
   #result.add getAst(echoString("  " & inst.repr))
   #result.add getAst(echoString("  " & impl0.repr))
   #result.add getAst(echoString("  " & impl.repr))
+
   if recurse:
-    template testDecl(n, m :typed) =
+    # now test using a newly formed variable of type getTypeInst(x)
+    template testDecl(n,m: typed) =
       testV(n, false):
         type _ = m
     result.add getAst(testDecl(inst.symToIdent, impl.symToIdent))
 
+# test with a variable (instance) of type
 template testV(inst, recurse, impl) =
   block:
     #echo "testV(" & astToStr(inst) & ", " & $recurse & "):" & astToStr(impl)
     var x: inst
     testX(x, inst, recurse, impl)
-template testT(inst, recurse) =
+
+# test with a newly created typedesc (myType)
+# using the passed type as the implementation
+template testT(impl, recurse) =
   block:
-    type myType = inst
+    type myType = impl
     testV(myType, recurse):
-      type _ = inst
+      type _ = impl
 
+# test a built-in type whose instance is equal to the implementation
 template test(inst) =
   testT(inst, false)
   testV(inst, true, nil)
-template test(inst, impl) = testV(inst, true, impl)
+
+# test a custom type with provided implementation
+template test(inst, impl) =
+  testV(inst, true, impl)
 
 type
   Model = object of RootObj
@@ -87,9 +105,12 @@ type
     value:T
   Foo[N:static[int],T] = object
   Bar[N:static[int],T] = object
-    #baz:Foo[N+1,GenericObject[T]]
+    #baz:Foo[N+1,GenericObject[T]]  # currently fails
     baz:Foo[N,GenericObject[T]]
 
+  Generic[T] = seq[int]
+  Concrete = Generic[int]
+
 test(bool)
 test(char)
 test(int)
@@ -97,13 +118,17 @@ test(float)
 test(ptr int)
 test(ref int)
 test(array[1..10,Bar[2,Foo[3,float]]])
+test(array[MyEnum,Bar[2,Foo[3,float]]])
 test(distinct Bar[2,Foo[3,float]])
 test(tuple[a:int,b:Foo[-1,float]])
-#test(MyEnum):
-#  type _ = enum
-#    valueA, valueB, valueC
-test(set[MyEnum])
 test(seq[int])
+test(set[MyEnum])
+test(proc (a: int, b: Foo[2,float]))
+test(proc (a: int, b: Foo[2,float]): Bar[3,int])
+
+test(MyEnum):
+  type _ = enum
+    valueA, valueB, valueC
 test(Bar[2,Foo[3,float]]):
   type _ = object
     baz: Foo[2, GenericObject[Foo[3, float]]]
@@ -118,8 +143,12 @@ test(Tree):
     value: int
     left: ref Tree
     right: ref Tree
-test(proc (a: int, b: Foo[2,float]))
-test(proc (a: int, b: Foo[2,float]): Bar[3,int])
+test(Concrete):
+  type _ = Generic[int]
+test(Generic[int]):
+  type _ = seq[int]
+test(Generic[float]):
+  type _ = seq[int]
 
 # bug #4862
 static:
diff --git a/web/news/e031_version_0_16_2.rst b/web/news/e031_version_0_16_2.rst
index 63884700f..4f49bd8d9 100644
--- a/web/news/e031_version_0_16_2.rst
+++ b/web/news/e031_version_0_16_2.rst
@@ -45,6 +45,8 @@ Changes affecting backwards compatibility
   AST that is the same as what is used to define an enum.  Previously the AST
   returned had a repeated ``EnumTy`` node and was missing the initial pragma
   node (which is currently empty for an enum).
+- ``macros.getTypeImpl`` now correctly returns the implementation for a symbol
+  of type ``tyGenericBody``.
 - If the dispatcher parameter's value used in multi method is ``nil``,
   a ``NilError`` exception is raised. The old behavior was that the method
   would be a ``nop`` then.