fix semFinishOperand for bracket expressions

fixes nim-lang#23568, fixes nim-lang#23310

compiler/semexprs.nim

@@ -1021,10 +1021,14 @@ proc finishOperand(c: PContext, a: PNode): PNode =
     localError(c.config, a.info, err)
   considerGenSyms(c, result)
 
-proc semFinishOperands(c: PContext; n: PNode) =
+proc semFinishOperands(c: PContext; n: PNode; isBracketExpr = false) =
   # this needs to be called to ensure that after overloading resolution every
-  # argument has been sem'checked:
-  for i in 1..<n.len:
+  # argument has been sem'checked
+
+  # skip the first argument for operands of `[]` since it may be an unresolved
+  # generic proc, which is handled in semMagic
+  let start = 1 + ord(isBracketExpr)
+  for i in start..<n.len:
     n[i] = finishOperand(c, n[i])
 
 proc afterCallActions(c: PContext; n, orig: PNode, flags: TExprFlags; expectedType: PType = nil): PNode =
@@ -1047,10 +1051,7 @@ proc afterCallActions(c: PContext; n, orig: PNode, flags: TExprFlags; expectedTy
   of skMacro: result = semMacroExpr(c, result, orig, callee, flags, expectedType)
   of skTemplate: result = semTemplateExpr(c, result, callee, flags, expectedType)
   else:
-    if callee.magic notin {mArrGet, mArrPut, mNBindSym}:
-      # calls to `[]` can be explicit generic instantiations,
-      # don't sem every operand now, leave it to semmagic
-      semFinishOperands(c, result)
+    semFinishOperands(c, result, isBracketExpr = callee.magic in {mArrGet, mArrPut})
     activate(c, result)
     fixAbstractType(c, result)
     analyseIfAddressTakenInCall(c, result)

tests/generics/tnestedissues.nim

@@ -0,0 +1,24 @@
+block: # issue #23568
+  type G[T] = object
+    j: T
+  proc s[T](u: int) = discard
+  proc s[T]() = discard
+  proc c(e: int | int): G[G[G[int]]] = s[G[G[int]]]()
+  discard c(0)
+
+import std/options
+
+block: # issue #23310
+  type
+    BID = string or uint64
+    Future[T] = ref object of RootObj
+      internalValue: T
+    InternalRaisesFuture[T] = ref object of Future[T]
+  proc newInternalRaisesFutureImpl[T](): InternalRaisesFuture[T] =
+    let fut = InternalRaisesFuture[T]()
+  template newFuture[T](): auto =
+    newInternalRaisesFutureImpl[T]()
+  proc problematic(blockId: BID): Future[Option[seq[int]]] =
+    let resultFuture = newFuture[Option[seq[int]]]()
+    return resultFuture
+  let x = problematic("latest")