Merge pull request #3291 from yglukhov/nimvm-generic-fix

Fixed when nimvm in generics.

compiler/semexprs.nim

@@ -124,6 +124,9 @@ proc semSym(c: PContext, n: PNode, s: PSym, flags: TExprFlags): PNode =
         return newSymNode(u, n.info)
     result = newSymNode(s, n.info)
   of skVar, skLet, skResult, skForVar:
+    if s.magic == mNimvm:
+      localError(n.info, "illegal context for 'nimvm' magic")
+
     markUsed(n.info, s)
     styleCheckUse(n.info, s)
     # if a proc accesses a global variable, it is not side effect free:
@@ -1769,9 +1772,14 @@ proc semWhen(c: PContext, n: PNode, semCheck = true): PNode =
   #   ...
   # else:
   #   ...
-  let whenNimvm = n.sons.len == 2 and n.sons[0].kind == nkElifBranch and
-      n.sons[1].kind == nkElse and n.sons[0].sons[0].kind == nkIdent and
-      lookUp(c, n.sons[0].sons[0]).magic == mNimvm
+  var whenNimvm = false
+  if n.sons.len == 2 and n.sons[0].kind == nkElifBranch and
+      n.sons[1].kind == nkElse:
+    let exprNode = n.sons[0].sons[0]
+    if exprNode.kind == nkIdent:
+      whenNimvm = lookUp(c, exprNode).magic == mNimvm
+    elif exprNode.kind == nkSym:
+      whenNimvm = exprNode.sym.magic == mNimvm
 
   for i in countup(0, sonsLen(n) - 1):
     var it = n.sons[i]

compiler/semfold.nim

@@ -640,8 +640,6 @@ proc getConstExpr(m: PSym, n: PNode): PNode =
       of mNaN: result = newFloatNodeT(NaN, n)
       of mInf: result = newFloatNodeT(Inf, n)
       of mNegInf: result = newFloatNodeT(NegInf, n)
-      of mNimvm:
-        localError(n.info, "illegal context for 'nimvm' magic")
       else:
         if sfFakeConst notin s.flags: result = copyTree(s.ast)
     of {skProc, skMethod}:

lib/system.nim

@@ -1173,12 +1173,12 @@ const
     ## "i386", "alpha", "powerpc", "powerpc64", "powerpc64el", "sparc",
     ## "amd64", "mips", "mipsel", "arm", "arm64".
 
-  nimvm* {.magic: "Nimvm".}: bool = false
+  seqShallowFlag = low(int)
+
+let nimvm* {.magic: "Nimvm".}: bool = false
     ## may be used only in "when" expression.
     ## It is true in Nim VM context and false otherwise
 
-  seqShallowFlag = low(int)
-
 proc compileOption*(option: string): bool {.
   magic: "CompileOption", noSideEffect.}
   ## can be used to determine an on|off compile-time option. Example: