Disable the new generic params handling for immediate template and macros

Since immediate templates are not subjected to the standard sigmatching
algorithm, they will have a number of deficiencies when it comes to generic
params: Type dependencies between the parameters won't be honoured
and the bound generic symbols won't be resolvable within their bodies.
We could try to fix this, but it may be wiser to just deprecate immediate
templates and macros now that we have working untyped parameters.

Disabling the new features is admittedly not the greatest way to handle
this situations as it introduces inconsistency in the language, but at least
it makes the code backwards-compatible with the previous version of the
compiler instead of triggering more serious problems.

compiler/evaltempl.nim

@@ -66,7 +66,16 @@ proc evalTemplateArgs(n: PNode, s: PSym): PNode =
     else: 0
 
   var
-    genericParams = s.ast[genericParamsPos].len
+    # XXX: Since immediate templates are not subjected to the
+    # standard sigmatching algorithm, they will have a number
+    # of deficiencies when it comes to generic params:
+    # Type dependencies between the parameters won't be honoured
+    # and the bound generic symbols won't be resolvable within
+    # their bodies. We could try to fix this, but it may be
+    # wiser to just deprecate immediate templates and macros
+    # now that we have working untyped parameters.
+    genericParams = if sfImmediate in s.flags: 0
+                    else: s.ast[genericParamsPos].len
     expectedRegularParams = <s.typ.len
     givenRegularParams = totalParams - genericParams
 
@@ -81,6 +90,7 @@ proc evalTemplateArgs(n: PNode, s: PSym): PNode =
   # not supplied by the user
   for i in givenRegularParams+1 .. expectedRegularParams:
     let default = s.typ.n.sons[i].sym.ast
+    internalAssert default != nil
     if default.kind == nkEmpty:
       localError(n.info, errWrongNumberOfArguments)
       addSon(result, ast.emptyNode)

compiler/vm.nim

@@ -1521,10 +1521,11 @@ proc evalMacroCall*(module: PSym, n, nOrig: PNode, sym: PSym): PNode =
   for i in 1.. <sym.typ.len:
     tos.slots[i] = setupMacroParam(n.sons[i], sym.typ.sons[i])
 
-  let gp = sym.ast[genericParamsPos]
-  for i in 0 .. <gp.len:
-    let idx = sym.typ.len + i
-    tos.slots[idx] = setupMacroParam(n.sons[idx], gp[i].sym.typ)
+  if sfImmediate notin sym.flags:
+    let gp = sym.ast[genericParamsPos]
+    for i in 0 .. <gp.len:
+      let idx = sym.typ.len + i
+      tos.slots[idx] = setupMacroParam(n.sons[idx], gp[i].sym.typ)
 
   # temporary storage:
   #for i in L .. <maxSlots: tos.slots[i] = newNode(nkEmpty)

compiler/vmgen.nim

@@ -1845,9 +1845,13 @@ proc genProc(c: PCtx; s: PSym): int =
     c.prc = p
     # iterate over the parameters and allocate space for them:
     genParams(c, s.typ.n)
+    
     # allocate additional space for any generically bound parameters
-    if s.kind == skMacro and s.ast[genericParamsPos].kind != nkEmpty:
+    if s.kind == skMacro and
+       sfImmediate notin s.flags and
+       s.ast[genericParamsPos].kind != nkEmpty:
       genGenericParams(c, s.ast[genericParamsPos])
+    
     if tfCapturesEnv in s.typ.flags:
       #let env = s.ast.sons[paramsPos].lastSon.sym
       #assert env.position == 2