nimvm is magic

compiler/ast.nim

@@ -605,7 +605,8 @@ type
     mNBindSym, mLocals, mNCallSite,
     mEqIdent, mEqNimrodNode, mSameNodeType, mGetImpl,
     mNHint, mNWarning, mNError,
-    mInstantiationInfo, mGetTypeInfo, mNGenSym
+    mInstantiationInfo, mGetTypeInfo, mNGenSym,
+    mNimvm
 
 # things that we can evaluate safely at compile time, even if not asked for it:
 const

compiler/semfold.nim

@@ -640,6 +640,8 @@ 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

@@ -1173,6 +1173,10 @@ const
     ## "i386", "alpha", "powerpc", "powerpc64", "powerpc64el", "sparc",
     ## "amd64", "mips", "mipsel", "arm", "arm64".
 
+  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 {.