replaces pairs with keys and items; saves 8 bytes (#21319)

replace `pairs` with `keys` and `items`

compiler/condsyms.nim

@@ -25,7 +25,7 @@ proc undefSymbol*(symbols: StringTableRef; symbol: string) =
 #  result = if isDefined(symbol): gSymbols[symbol] else: nil
 
 iterator definedSymbolNames*(symbols: StringTableRef): string =
-  for key, val in pairs(symbols):
+  for key in keys(symbols):
     yield key
 
 proc countDefinedSymbols*(symbols: StringTableRef): int =

compiler/semfold.nim

@@ -685,7 +685,7 @@ proc getConstExpr(m: PSym, n: PNode; idgen: IdGenerator; g: ModuleGraph): PNode
       n[0] = a
   of nkBracket, nkCurly:
     result = copyNode(n)
-    for i, son in n.pairs:
+    for son in n.items:
       var a = getConstExpr(m, son, idgen, g)
       if a == nil: return nil
       result.add a
@@ -709,7 +709,7 @@ proc getConstExpr(m: PSym, n: PNode; idgen: IdGenerator; g: ModuleGraph): PNode
     # tuple constructor
     result = copyNode(n)
     if (n.len > 0) and (n[0].kind == nkExprColonExpr):
-      for i, expr in n.pairs:
+      for expr in n.items:
         let exprNew = copyNode(expr) # nkExprColonExpr
         exprNew.add expr[0]
         let a = getConstExpr(m, expr[1], idgen, g)
@@ -717,7 +717,7 @@ proc getConstExpr(m: PSym, n: PNode; idgen: IdGenerator; g: ModuleGraph): PNode
         exprNew.add a
         result.add exprNew
     else:
-      for i, expr in n.pairs:
+      for expr in n.items:
         let a = getConstExpr(m, expr, idgen, g)
         if a == nil: return nil
         result.add a

compiler/seminst.nim

@@ -40,7 +40,7 @@ const
 
 iterator instantiateGenericParamList(c: PContext, n: PNode, pt: TIdTable): PSym =
   internalAssert c.config, n.kind == nkGenericParams
-  for i, a in n.pairs:
+  for a in n.items:
     internalAssert c.config, a.kind == nkSym
     var q = a.sym
     if q.typ.kind in {tyTypeDesc, tyGenericParam, tyStatic, tyConcept}+tyTypeClasses: