Add test coverage for lowering raw identifiers in function names (#4257)

toolchain/lower/testdata/function/definition/raw_name.carbon

@@ -0,0 +1,32 @@
+// 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
+//
+// AUTOUPDATE
+// TIP: To test this file alone, run:
+// TIP:   bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/lower/testdata/function/definition/raw_name.carbon
+// TIP: To dump output, run:
+// TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/function/definition/raw_name.carbon
+
+fn r#self() {}
+
+
+// CHECK:STDOUT: ; ModuleID = 'raw_name.carbon'
+// CHECK:STDOUT: source_filename = "raw_name.carbon"
+// CHECK:STDOUT:
+// CHECK:STDOUT: define void @self() !dbg !4 {
+// CHECK:STDOUT: entry:
+// CHECK:STDOUT:   ret void, !dbg !7
+// CHECK:STDOUT: }
+// 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, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
+// CHECK:STDOUT: !3 = !DIFile(filename: "raw_name.carbon", directory: "")
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "self", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
+// CHECK:STDOUT: !6 = !{}
+// CHECK:STDOUT: !7 = !DILocation(line: 11, column: 1, scope: !4)