[firtool] Change layer specialization CLI interface

lib/Dialect/FIRRTL/Import/FIRParser.cpp

@@ -5671,11 +5671,11 @@ ParseResult FIRCircuitParser::parseCircuit(
   // a SymbolRefAttr.
   auto parseLayerName = [&](StringRef name) {
     // Parse the layer name into a SymbolRefAttr.
-    auto [head, rest] = name.split("::");
+    auto [head, rest] = name.split(".");
     SmallVector<FlatSymbolRefAttr> nestedRefs;
     while (!rest.empty()) {
       StringRef next;
-      std::tie(next, rest) = rest.split("::");
+      std::tie(next, rest) = rest.split(".");
       nestedRefs.push_back(FlatSymbolRefAttr::get(getContext(), next));
     }
     return SymbolRefAttr::get(getContext(), head, nestedRefs);

test/firtool/specialize-layers-cli.fir

@@ -0,0 +1,21 @@
+; RUN: firtool -parse-only %s | FileCheck %s --check-prefixes=NONE
+; RUN: firtool -parse-only -disable-layers=A %s | FileCheck %s --check-prefixes=DISABLEA
+; RUN: firtool -parse-only -enable-layers=A %s | FileCheck %s --check-prefixes=ENABLEA
+; RUN: firtool -parse-only -enable-layers=A.B %s | FileCheck %s --check-prefixes=ENABLEB
+; RUN: firtool -parse-only -disable-layers=A,A.B %s | FileCheck %s --check-prefixes=DISABLEBOTH
+; RUN: firtool -parse-only -disable-layers=A -enable-layers=A.B %s | FileCheck %s --check-prefixes=BOTH
+
+; Check that the command line options are working correctly.
+; https://github.com/llvm/circt/issues/7345
+
+FIRRTL version 4.0.0
+; NONE:        firrtl.circuit "Foo" {
+; DISABLEA:    firrtl.circuit "Foo" attributes {disable_layers = [@A]} {
+; ENABLEA:     firrtl.circuit "Foo" attributes {enable_layers = [@A]} {
+; ENABLEB:     firrtl.circuit "Foo" attributes {enable_layers = [@A::@B]} {
+; DISABLEBOTH: firrtl.circuit "Foo" attributes {disable_layers = [@A, @A::@B]} {
+; BOTH:        firrtl.circuit "Foo" attributes {disable_layers = [@A], enable_layers = [@A::@B]} {
+circuit Foo:
+  layer A, bind:
+    layer B, bind:
+  public module Foo: