Adjust LDBG output: surround DebugType between [ and ] (llvm#150671)

This makes the output more readable by clearly showing the current debug
type as a keyword.

Author: joker-eph

llvm/include/llvm/Support/DebugLog.h

@@ -38,8 +38,8 @@ class LogWithNewline {
                  raw_ostream &os)
       : os(os) {
     if (debug_type)
-      os << debug_type << " ";
-    os << "[" << file << ":" << line << "] ";
+      os << "[" << debug_type << "] ";
+    os << file << ":" << line << " ";
   }
   ~LogWithNewline() { os << '\n'; }
   template <typename T> raw_ostream &operator<<(const T &t) && {

llvm/unittests/Support/DebugLogTest.cpp

@@ -27,7 +27,7 @@ TEST(DebugLogTest, Basic) {
     std::string str;
     raw_string_ostream os(str);
     DEBUGLOG_WITH_STREAM_AND_TYPE(os, nullptr) << "NoType";
-    EXPECT_TRUE(StringRef(os.str()).starts_with('['));
+    EXPECT_FALSE(StringRef(os.str()).starts_with('['));
     EXPECT_TRUE(StringRef(os.str()).ends_with("NoType\n"));
   }
 
@@ -37,6 +37,7 @@ TEST(DebugLogTest, Basic) {
     raw_string_ostream os(str);
     DEBUGLOG_WITH_STREAM_AND_TYPE(os, "A") << "A";
     DEBUGLOG_WITH_STREAM_AND_TYPE(os, "B") << "B";
+    EXPECT_TRUE(StringRef(os.str()).starts_with('['));
     EXPECT_THAT(os.str(), AllOf(HasSubstr("A\n"), HasSubstr("B\n")));
   }