[clang] [clang-format] Stop ctor initializer from being inlined (PR #150361)

[Eric Li via cfe-commits]

https://github.com/tJener updated https://github.com/llvm/llvm-project/pull/150361

>From 2c1a695bd602b45f68bdc97043ff2b144372230b Mon Sep 17 00:00:00 2001
From: Eric Li <li.zhe.hua at gmail.com>
Date: Wed, 23 Jul 2025 22:18:05 -0400
Subject: [PATCH 1/2] [clang-format] Stop ctor initializer from being inlined

The colon in a constructor's initializer list triggers the inlining of a nested
block as if it was a conditional operator expression. This prevents line breaks
under certain circumstances when the initializer list contains braced
initializers, which in turn prevents the line formatter from finding a solution.

In this commit we exclude colons that are a constructor initializer colon from
consideration of nested block inlining.
---
 clang/lib/Format/ContinuationIndenter.cpp |  3 ++-
 clang/unittests/Format/FormatTest.cpp     | 31 +++++++++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Format/ContinuationIndenter.cpp b/clang/lib/Format/ContinuationIndenter.cpp
index 4010f7fbd25be..83920ea492870 100644
--- a/clang/lib/Format/ContinuationIndenter.cpp
+++ b/clang/lib/Format/ContinuationIndenter.cpp
@@ -1724,7 +1724,8 @@ unsigned ContinuationIndenter::moveStateToNextToken(LineState &State,
   }
   if (Previous && (Previous->isOneOf(TT_BinaryOperator, TT_ConditionalExpr) ||
                    (Previous->isOneOf(tok::l_paren, tok::comma, tok::colon) &&
-                    !Previous->isOneOf(TT_DictLiteral, TT_ObjCMethodExpr)))) {
+                    !Previous->isOneOf(TT_DictLiteral, TT_ObjCMethodExpr,
+                                       TT_CtorInitializerColon)))) {
     CurrentState.NestedBlockInlined =
         !Newline && hasNestedBlockInlined(Previous, Current, Style);
   }
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 944e7c3fb152a..75bdb9444bc45 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -7771,6 +7771,37 @@ TEST_F(FormatTest, ConstructorInitializers) {
                "Constructor() :\n"
                "    // Comment forcing unwanted break.\n"
                "    aaaa(aaaa) {}");
+
+  // Braced initializers with trailing commas.
+  verifyFormat("MyClass::MyClass()\n"
+               "    : aaaa{\n"
+               "          0,\n"
+               "      } {}",
+               "MyClass::MyClass():aaaa{0,}{}", getGoogleStyle());
+  verifyFormat("MyClass::MyClass()\n"
+               "    : aaaa(0),\n"
+               "      bbbb{\n"
+               "          0,\n"
+               "      } {}",
+               "MyClass::MyClass():aaaa(0),bbbb{0,}{}", getGoogleStyle());
+  verifyFormat("MyClass::MyClass()\n"
+               "    : aaaa(0),\n"
+               "      bbbb{\n"
+               "          0,\n"
+               "      },\n"
+               "      cccc{\n"
+               "          0,\n"
+               "      } {}",
+               "MyClass::MyClass():aaaa(0),bbbb{0,},cccc{0,}{}",
+               getGoogleStyle());
+  verifyFormat("MyClass::MyClass()\n"
+               "    : aaaa{\n"
+               "          0,\n"
+               "      },\n"
+               "      bbbb{\n"
+               "          0,\n"
+               "      } {}",
+               "MyClass::MyClass():aaaa{0,},bbbb{0,}{}", getGoogleStyle());
 }
 
 TEST_F(FormatTest, AllowAllConstructorInitializersOnNextLine) {

>From 8c28f84f8c8a31356526fa37cca4a4bcdc7535da Mon Sep 17 00:00:00 2001
From: Eric Li <li.zhe.hua at gmail.com>
Date: Thu, 24 Jul 2025 03:44:23 -0400
Subject: [PATCH 2/2] fixup

---
 clang/unittests/Format/FormatTest.cpp | 23 +----------------------
 1 file changed, 1 insertion(+), 22 deletions(-)

diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 75bdb9444bc45..0d086bb5290e1 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -7773,27 +7773,6 @@ TEST_F(FormatTest, ConstructorInitializers) {
                "    aaaa(aaaa) {}");
 
   // Braced initializers with trailing commas.
-  verifyFormat("MyClass::MyClass()\n"
-               "    : aaaa{\n"
-               "          0,\n"
-               "      } {}",
-               "MyClass::MyClass():aaaa{0,}{}", getGoogleStyle());
-  verifyFormat("MyClass::MyClass()\n"
-               "    : aaaa(0),\n"
-               "      bbbb{\n"
-               "          0,\n"
-               "      } {}",
-               "MyClass::MyClass():aaaa(0),bbbb{0,}{}", getGoogleStyle());
-  verifyFormat("MyClass::MyClass()\n"
-               "    : aaaa(0),\n"
-               "      bbbb{\n"
-               "          0,\n"
-               "      },\n"
-               "      cccc{\n"
-               "          0,\n"
-               "      } {}",
-               "MyClass::MyClass():aaaa(0),bbbb{0,},cccc{0,}{}",
-               getGoogleStyle());
   verifyFormat("MyClass::MyClass()\n"
                "    : aaaa{\n"
                "          0,\n"
@@ -7801,7 +7780,7 @@ TEST_F(FormatTest, ConstructorInitializers) {
                "      bbbb{\n"
                "          0,\n"
                "      } {}",
-               "MyClass::MyClass():aaaa{0,},bbbb{0,}{}", getGoogleStyle());
+               "MyClass::MyClass():aaaa{0,},bbbb{0,}{}");
 }
 
 TEST_F(FormatTest, AllowAllConstructorInitializersOnNextLine) {