correct comparisons for nil strings/seqs

compiler/ccgexprs.nim

@@ -980,10 +980,10 @@ proc genEcho(p: BProc, n: PNode) =
     var a: TLoc
     for it in n.sons:
       if it.skipConv.kind == nkNilLit:
-        add(args, ", \"nil\"")
+        add(args, ", \"\"")
       else:
         initLocExpr(p, it, a)
-        addf(args, ", $1? ($1)->data:\"nil\"", [rdLoc(a)])
+        addf(args, ", $1? ($1)->data:\"\"", [rdLoc(a)])
     p.module.includeHeader("<base/log.h>")
     linefmt(p, cpsStmts, """Genode::log(""$1);$n""", args)
   else:
@@ -1755,16 +1755,14 @@ proc genStrEquals(p: BProc, e: PNode, d: var TLoc) =
   var x: TLoc
   var a = e.sons[1]
   var b = e.sons[2]
-  if (a.kind == nkNilLit) or (b.kind == nkNilLit):
-    binaryExpr(p, e, d, "($1 == $2)")
-  elif (a.kind in {nkStrLit..nkTripleStrLit}) and (a.strVal == ""):
+  if a.kind in {nkStrLit..nkTripleStrLit} and a.strVal == "":
     initLocExpr(p, e.sons[2], x)
     putIntoDest(p, d, e,
-      rfmt(nil, "(($1) && ($1)->$2 == 0)", rdLoc(x), lenField(p)))
-  elif (b.kind in {nkStrLit..nkTripleStrLit}) and (b.strVal == ""):
+      rfmt(nil, "(!($1) || ($1)->$2 == 0)", rdLoc(x), lenField(p)))
+  elif b.kind in {nkStrLit..nkTripleStrLit} and b.strVal == "":
     initLocExpr(p, e.sons[1], x)
     putIntoDest(p, d, e,
-      rfmt(nil, "(($1) && ($1)->$2 == 0)", rdLoc(x), lenField(p)))
+      rfmt(nil, "(!($1) || ($1)->$2 == 0)", rdLoc(x), lenField(p)))
   else:
     binaryExpr(p, e, d, "#eqStrings($1, $2)")
 

compiler/condsyms.nim

@@ -82,7 +82,6 @@ proc countDefinedSymbols*(): int =
 
 proc initDefines*() =
   gSymbols = newStringTable(modeStyleInsensitive)
-  defineSymbol("nimrod") # 'nimrod' is always defined
   # for bootstrapping purposes and old code:
   defineSymbol("nimhygiene")
   defineSymbol("niminheritable")
@@ -115,3 +114,4 @@ proc initDefines*() =
   defineSymbol("nimHasNilChecks")
   defineSymbol("nimSymKind")
   defineSymbol("nimVmEqIdent")
+  defineSymbol("nimNoNil")

compiler/vmgen.nim

@@ -1553,6 +1553,7 @@ proc getNullValue(typ: PType, info: TLineInfo): PNode =
     result = newNodeIT(nkFloatLit, info, t)
   of tyCString, tyString:
     result = newNodeIT(nkStrLit, info, t)
+    result.strVal = ""
   of tyVar, tyLent, tyPointer, tyPtr, tySequence, tyExpr,
      tyStmt, tyTypeDesc, tyStatic, tyRef, tyNil:
     result = newNodeIT(nkNilLit, info, t)