Detangle CHECK() failures from std::ostream

This adjusts code paths to not rely on streaming CHECK() failures to a
std::ostream, which required both that an underlying ostream object
exists and that the logged type was not the first argument streamed to
a CHECK() failure.

This intends to unlock further optimizations (can skip logging steps) as
no std::ostream object needs to be generated. This may be used for
skipping constant strings in official builds where they don't contribute
to debuggability (i.e. streaming a string constant may for instance just
return *this).

Bug: 378574882
Change-Id: I594c1fec8ed8757ac54ecef5239de24db82a80cb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6332885
Owners-Override: Peter Kasting <pkasting@chromium.org>
Auto-Submit: Peter Boström <pbos@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Commit-Queue: Peter Boström <pbos@chromium.org>
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1430504}

ash/wm/overview/birch/birch_bar_view.cc

@@ -6,6 +6,7 @@
 
 #include <array>
 #include <ostream>
+#include <string_view>
 #include <vector>
 
 #include "ash/birch/birch_item.h"
@@ -125,20 +126,20 @@ bool IsLoadingState(State state) {
 
 #if DCHECK_IS_ON()
 // Gets the string of given state.
-std::ostream& operator<<(std::ostream& stream, State state) {
+std::string_view ToString(State state) {
   switch (state) {
     case State::kLoading:
-      return stream << "loading";
+      return "loading";
     case State::kLoadingForInformedRestore:
-      return stream << "loading for informed restore";
+      return "loading for informed restore";
     case State::kLoadingByUser:
-      return stream << "loading by user";
+      return "loading by user";
     case State::kReloading:
-      return stream << "reloading";
+      return "reloading";
     case State::kShuttingDown:
-      return stream << "shutting down";
+      return "shutting down";
     case State::kNormal:
-      return stream << "normal";
+      return "normal";
   }
 }
 
@@ -227,8 +228,8 @@ void BirchBarView::SetState(State state) {
 
 #if DCHECK_IS_ON()
   if (!IsValidStateTransition(state_, state)) {
-    NOTREACHED() << "Transition from state " << state_ << " to state " << state
-                 << " is invalid.";
+    NOTREACHED() << "Transition from state " << ToString(state_) << " to state "
+                 << ToString(state) << " is invalid.";
   }
 #endif
 

base/check.h

@@ -135,8 +135,9 @@ class BASE_EXPORT CheckError {
   CheckError& operator=(const CheckError&) = delete;
 
   template <typename T>
-  std::ostream& operator<<(T&& streamed_type) {
-    return stream() << streamed_type;
+  CheckError& operator<<(T&& streamed_type) {
+    stream() << streamed_type;
+    return *this;
   }
 
  protected:

components/viz/common/yuv_readback_unittest.cc

@@ -91,7 +91,7 @@ class YUVReadbackTest : public testing::Test {
     auto parsed_json = base::JSONReader::ReadAndReturnValueWithError(json_data);
     CHECK(parsed_json.has_value())
         << "JSON parsing failed (" << parsed_json.error().message
-        << ") JSON data:" << std::endl
+        << ") JSON data:\n"
         << json_data;
 
     CHECK(parsed_json->is_list());

services/webnn/public/cpp/webnn_trace_unittest.cc

@@ -72,7 +72,7 @@ class ScopedTraceTest : public testing::Test {
         base::JSONReader::ReadAndReturnValueWithError(json_data.json_output);
     CHECK(parsed_json.has_value())
         << "JSON parsing failed (" << parsed_json.error().message
-        << ") JSON data:" << std::endl
+        << ") JSON data:\n"
         << json_data.json_output;
 
     CHECK(parsed_json->is_list());

third_party/blink/renderer/core/editing/editing_utilities.cc

@@ -26,6 +26,7 @@
 #include "third_party/blink/renderer/core/editing/editing_utilities.h"
 
 #include <array>
+#include <string_view>
 
 #include "base/trace_event/trace_event.h"
 #include "third_party/blink/renderer/core/clipboard/clipboard_mime_types.h"
@@ -105,12 +106,12 @@ using mojom::blink::FormControlType;
 
 namespace {
 
-std::ostream& operator<<(std::ostream& os, PositionMoveType type) {
-  static const std::array<const char*, 3> kTexts = {
+std::string_view ToString(PositionMoveType type) {
+  static const std::array<std::string_view, 3> kTexts = {
       "CodeUnit", "BackwardDeletion", "GraphemeCluster"};
   DCHECK_LT(static_cast<size_t>(type), kTexts.size())
       << "Unknown PositionMoveType value";
-  return os << kTexts[static_cast<size_t>(type)];
+  return kTexts[static_cast<size_t>(type)];
 }
 
 UChar WhitespaceRebalancingCharToAppend(const String& string,
@@ -743,7 +744,7 @@ PositionTemplate<Strategy> PreviousPositionOfAlgorithm(
         return PositionTemplate<Strategy>(
             node, PreviousGraphemeBoundaryOf(*node, offset));
       default:
-        NOTREACHED() << "Unhandled moveType: " << move_type;
+        NOTREACHED() << "Unhandled moveType: " << ToString(move_type);
     }
   }
 
@@ -805,7 +806,7 @@ PositionTemplate<Strategy> NextPositionOfAlgorithm(
         return PositionTemplate<Strategy>::EditingPositionOf(
             node, NextGraphemeBoundaryOf(*node, offset));
       default:
-        NOTREACHED() << "Unhandled moveType: " << move_type;
+        NOTREACHED() << "Unhandled moveType: " << ToString(move_type);
     }
   }