fix nim-lang#14340 (nim-lang#16386)

compiler/ccgexprs.nim

@@ -3094,7 +3094,9 @@ proc genBracedInit(p: BProc, n: PNode; isConst: bool; optionalType: PType): Rope
       else:
         result = genConstSeq(p, n, typ, isConst)
     of tyProc:
-      if typ.callConv == ccClosure and n.len > 1 and n[1].kind == nkNilLit:
+      if typ.callConv == ccClosure and n.safeLen > 1 and n[1].kind == nkNilLit:
+        # n.kind could be: nkClosure, nkTupleConstr and maybe others; `n.safeLen`
+        # guards against the case of `nkSym`, refs bug #14340.
         # Conversion: nimcall -> closure.
         # this hack fixes issue that nkNilLit is expanded to {NIM_NIL,NIM_NIL}
         # this behaviour is needed since closure_var = nil must be

tests/vm/tvmmisc.nim

@@ -306,6 +306,23 @@ block: # bug #8007
   const d = @[Cost(kind: Fixed, cost: 999), Cost(kind: Dynamic, handler: foo)]
   doAssert $d == "@[(kind: Fixed, cost: 999), (kind: Dynamic, handler: ...)]"
 
+block: # bug #14340
+  block:
+    proc opl3EnvelopeCalcSin0() = discard
+    type EnvelopeSinfunc = proc()
+    # const EnvelopeCalcSin0 = opl3EnvelopeCalcSin0 # ok
+    const EnvelopeCalcSin0: EnvelopeSinfunc = opl3EnvelopeCalcSin0 # was bug
+    const envelopeSin = [EnvelopeCalcSin0]
+    var a = 0
+    envelopeSin[a]()
+
+  block:
+    type Mutator = proc() {.noSideEffect, gcsafe, locks: 0.}
+    proc mutator0() = discard
+    const mTable = [Mutator(mutator0)]
+    var i=0
+    mTable[i]()
+
 block: # VM wrong register free causes errors in unrelated code
   block: # bug #15597
     #[