fix #986

compiler/semexprs.nim

@@ -899,6 +899,21 @@ proc makeDeref(n: PNode): PNode =
     addSon(result, a)
     t = skipTypes(t.sons[0], {tyGenericInst})
 
+proc readTypeParameter(c: PContext, ty: PType,
+                       paramName: PIdent, info: TLineInfo): PNode =
+  internalAssert ty.kind == tyGenericInst
+  let ty = ty.skipGenericAlias
+  let tbody = ty.sons[0]
+  for s in countup(0, tbody.len-2):
+    let tParam = tbody.sons[s]
+    if tParam.sym.name == paramName:
+      let rawTyp = ty.sons[s + 1]
+      if rawTyp.kind == tyStatic:
+        return rawTyp.n
+      else:
+        let foundTyp = makeTypeDesc(c, rawTyp)
+        return newSymNode(copySym(tParam.sym).linkTo(foundTyp), info)
+
 proc builtinFieldAccess(c: PContext, n: PNode, flags: TExprFlags): PNode =
   ## returns nil if it's not a built-in field access
   checkSonsLen(n, 2)
@@ -932,18 +947,7 @@ proc builtinFieldAccess(c: PContext, n: PNode, flags: TExprFlags): PNode =
         markUsed(n, f)
         return
     of tyGenericInst:
-      assert ty.sons[0].kind == tyGenericBody
+      return readTypeParameter(c, ty, i, n.info)
-      let tbody = ty.sons[0]
-      for s in countup(0, tbody.len-2):
-        let tParam = tbody.sons[s]
-        if tParam.sym.name == i:
-          let rawTyp = ty.sons[s + 1]
-          if rawTyp.kind == tyStatic:
-            return rawTyp.n
-          else:
-            let foundTyp = makeTypeDesc(c, rawTyp)
-            return newSymNode(copySym(tParam.sym).linkTo(foundTyp), n.info)
-      return
     of tyObject, tyTuple:
       if ty.n.kind == nkRecList:
         for field in ty.n.sons:
@@ -990,6 +994,10 @@ proc builtinFieldAccess(c: PContext, n: PNode, flags: TExprFlags): PNode =
       n.typ = f.typ
       result = n
 
+  # we didn't find any field, let's look for a generic param
+  if result == nil and n.sons[0].typ.kind == tyGenericInst:
+    result = readTypeParameter(c, n.sons[0].typ, i, n.info)
+
 proc dotTransformation(c: PContext, n: PNode): PNode =
   if isSymChoice(n.sons[1]):
     result = newNodeI(nkDotCall, n.info)

compiler/semtypinst.nim

@@ -181,7 +181,8 @@ proc replaceTypeVarsN(cl: var TReplTypeVars, n: PNode): PNode =
   of nkStaticExpr:
     var n = prepareNode(cl, n)
     n = reResolveCallsWithTypedescParams(cl, n)
-    result = cl.c.semExpr(cl.c, n)
+    result = if cl.allowMetaTypes: n
+             else: cl.c.semExpr(cl.c, n)
   else:
     var length = sonsLen(n)
     if length > 0:
@@ -341,6 +342,7 @@ proc replaceTypeVarsTAux(cl: var TReplTypeVars, t: PType): PType =
     result = replaceTypeVarsT(cl, lastSon(t))
 
   of tyFromExpr:
+    if cl.allowMetaTypes: return
     var n = prepareNode(cl, t.n)
     n = cl.c.semConstExpr(cl.c, n)
     if n.typ.kind == tyTypeDesc:

tests/metatype/tstaticparams.nim

@@ -1,6 +1,6 @@
 discard """
   file: "tstaticparams.nim"
-  output: "abracadabra\ntest\n3\n15"
+  output: "abracadabra\ntest\n3\n15\4"
 """
 
 type 
@@ -41,3 +41,7 @@ type
 var m: AffineTransform3D[float]
 echo high(m)
 
+proc getRows(mtx: Matrix): int =
+  result = mtx.M
+
+echo getRows(m)