Working test cases for the sophisticated matrix library example from the manual

Fixed the dot operator when used within return types (see tgenericdotrettype)
Fixed the matching of generic concepts aliases used with the implicit generics style

compiler/sigmatch.nim

@@ -613,26 +613,34 @@ proc matchUserTypeClass*(c: PContext, m: var TCandidate,
       template paramSym(kind): untyped =
         newSym(kind, typeParamName, Concept.sym, Concept.sym.info)
 
-      case typ.kind
-      of tyStatic:
-        param = paramSym skConst
-        param.typ = typ.exactReplica
-        if typ.n == nil:
-          param.typ.flags.incl tfInferrableStatic
-        else:
-          param.ast = typ.n
-      of tyUnknown:
-        param = paramSym skVar
-        param.typ = typ.exactReplica
-      else:
-        param = paramSym skType
-        param.typ = if typ.isMetaType:
-                      c.newTypeWithSons(tyInferred, @[typ])
-                    else:
-                      makeTypeDesc(c, typ)
+      block addTypeParam:
+        for prev in typeParams:
+          if prev[1].id == typ.id:
+            param = paramSym prev[0].kind
+            param.typ = prev[0].typ
+            break addTypeParam
 
+        case typ.kind
+        of tyStatic:
+          param = paramSym skConst
+          param.typ = typ.exactReplica
+          if typ.n == nil:
+            param.typ.flags.incl tfInferrableStatic
+          else:
+            param.ast = typ.n
+        of tyUnknown:
+          param = paramSym skVar
+          param.typ = typ.exactReplica
+        else:
+          param = paramSym skType
+          param.typ = if typ.isMetaType:
+                        c.newTypeWithSons(tyInferred, @[typ])
+                      else:
+                        makeTypeDesc(c, typ)
+
+        typeParams.safeAdd((param, typ))
+      
       addDecl(c, param)
-      typeParams.safeAdd((param, typ))
 
   for param in Concept.n[0]:
     var
@@ -682,7 +690,7 @@ proc matchUserTypeClass*(c: PContext, m: var TCandidate,
       diagnostics.add msg
    
   var checkedBody = c.semTryExpr(c, body.copyTree, flags)
-  
+
   if collectDiagnostics:
     writelnHook = oldWriteHook
     for msg in diagnostics: m.diagnostics.safeAdd msg
@@ -696,7 +704,7 @@ proc matchUserTypeClass*(c: PContext, m: var TCandidate,
     put(m.bindings, p[1], p[0].typ)
 
   if ff.kind == tyUserTypeClassInst:
-    result = generateTypeInstance(c, m.bindings, ff.sym.info, ff)
+    result = generateTypeInstance(c, m.bindings, Concept.sym.info, ff)
   else:
     result = copyType(ff, ff.owner, true)