Add comment and test for special case in `NameRef` lowering (#7008)

toolchain/lower/handle.cpp

@@ -226,6 +226,11 @@ auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
 
   auto inner_inst_id = inst.value_id;
 
+  // `GetValue` will fail on package-scope value bindings because they aren't
+  // constants, and they aren't global variables, so as a workaround we
+  // peek through bindings here to directly access the bound value.
+  // TODO: Find a way of dealing with this that still works if the bound
+  // value isn't a global variable or constant either.
   if (auto bind_name =
           context.sem_ir().insts().TryGetAs<SemIR::AnyBinding>(inner_inst_id)) {
     inner_inst_id = bind_name->value_id;

toolchain/lower/testdata/let/global.carbon

@@ -0,0 +1,60 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+// INCLUDE-FILE: toolchain/testing/testdata/min_prelude/none.carbon
+//
+// AUTOUPDATE
+// TIP: To test this file alone, run:
+// TIP:   bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/lower/testdata/let/global.carbon
+// TIP: To dump output, run:
+// TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/let/global.carbon
+
+class C {}
+
+let c: C = {};
+
+fn Sink(_: C);
+
+fn F() {
+  Sink(c);
+}
+
+// CHECK:STDOUT: ; ModuleID = 'global.carbon'
+// CHECK:STDOUT: source_filename = "global.carbon"
+// CHECK:STDOUT:
+// CHECK:STDOUT: @C.val = internal constant {} zeroinitializer
+// CHECK:STDOUT: @C.val.loc15_13.5 = internal constant {} zeroinitializer
+// CHECK:STDOUT: @llvm.global_ctors = appending global [1 x { i32, ptr, ptr }] [{ i32, ptr, ptr } { i32 0, ptr @_C__global_init.Main, ptr null }]
+// CHECK:STDOUT:
+// CHECK:STDOUT: declare void @_CSink.Main(ptr)
+// CHECK:STDOUT:
+// CHECK:STDOUT: ; Function Attrs: nounwind
+// CHECK:STDOUT: define void @_CF.Main() #0 !dbg !4 {
+// CHECK:STDOUT: entry:
+// CHECK:STDOUT:   call void @_CSink.Main(ptr @C.val.loc15_13.5), !dbg !7
+// CHECK:STDOUT:   ret void, !dbg !8
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: ; Function Attrs: nounwind
+// CHECK:STDOUT: define internal void @_C__global_init.Main() #0 !dbg !9 {
+// CHECK:STDOUT: entry:
+// CHECK:STDOUT:   ret void, !dbg !10
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: attributes #0 = { nounwind }
+// CHECK:STDOUT:
+// CHECK:STDOUT: !llvm.module.flags = !{!0, !1}
+// CHECK:STDOUT: !llvm.dbg.cu = !{!2}
+// CHECK:STDOUT:
+// CHECK:STDOUT: !0 = !{i32 7, !"Dwarf Version", i32 5}
+// CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
+// CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
+// CHECK:STDOUT: !3 = !DIFile(filename: "global.carbon", directory: "")
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "_CF.Main", scope: null, file: !3, line: 19, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
+// CHECK:STDOUT: !6 = !{null}
+// CHECK:STDOUT: !7 = !DILocation(line: 20, column: 3, scope: !4)
+// CHECK:STDOUT: !8 = !DILocation(line: 19, column: 1, scope: !4)
+// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "__global_init", linkageName: "_C__global_init.Main", scope: null, file: !3, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !10 = !DILocation(line: 0, scope: !9)