new-style concepts implementation, WIP (#15251)

* fixes #15210 [backport:1.2]

* make tests green
* make ordinal work
* makes Swapable test compile
* make Indexable example work
* concepts: 'self' is now 'Self'
* concepts: make Dictionary example compile
* document the new concept implementation
* concepts: make typeDesc work properly
* concepts: allow documentation comments (d'oh)

compiler/semdata.nim

@@ -153,7 +153,7 @@ type
     suggestionsMade*: bool
     isAmbiguous*: bool # little hack
     features*: set[Feature]
-    inTypeContext*: int
+    inTypeContext*, inConceptDecl*: int
     unusedImports*: seq[(PSym, TLineInfo)]
     exportIndirections*: HashSet[(int, int)]
     lastTLineInfo*: TLineInfo
@@ -410,14 +410,6 @@ proc makeVarType*(owner: PSym, baseType: PType; idgen: IdGenerator; kind = tyVar
     result = newType(kind, nextTypeId(idgen), owner)
     addSonSkipIntLit(result, baseType, idgen)
 
-proc makeTypeDesc*(c: PContext, typ: PType): PType =
-  if typ.kind == tyTypeDesc:
-    result = typ
-  else:
-    result = newTypeS(tyTypeDesc, c)
-    incl result.flags, tfCheckedForDestructor
-    result.addSonSkipIntLit(typ, c.idgen)
-
 proc makeTypeSymNode*(c: PContext, typ: PType, info: TLineInfo): PNode =
   let typedesc = newTypeS(tyTypeDesc, c)
   incl typedesc.flags, tfCheckedForDestructor