[clang-format] Do not remove required spaces when aligning tokens.

[curdeius]

Summary

Fixes https://github.com/llvm/llvm-project/issues/44292.
Fixes https://github.com/llvm/llvm-project/issues/45874.

[curdeius]

clang/lib/Format/WhitespaceManager.cpp

334–337

On a second thought, it seems like a workaround only and a real solution would be to fix https://github.com/llvm/llvm-project/issues/53699 that I've just created.
It fixes an immediate problem though.
I'll add a fixme in a later revision (or when landing) to remove this when the abovementioned bug is solved properly.
Then, this problem should be caught by the assertion added later below.

[owenpan]

clang/lib/Format/WhitespaceManager.cpp

409

clang/unittests/Format/FormatTest.cpp

17287

17298

[curdeius]

Address review comments. Add a fixme note.

clang/lib/Format/WhitespaceManager.cpp

for (unsigned i = Start; i != End; ++i) {
 
     // If this is the first matching token to be aligned, remember by how many
     // spaces it has to be shifted, so the rest of the changes on the line are
     // shifted by the same amount
     if (!FoundMatchOnLine && !SkipMatchCheck && Matches(Changes[i])) {
       FoundMatchOnLine = true;
       Shift = Column - Changes[i].StartOfTokenColumn;
       Changes[i].Spaces += Shift;
+      // FIXME: This is a workaround that should be removed when we fix
+      // http://llvm.org/PR53699. An assertion later below verifies this.
+      if (Changes[i].NewlinesBefore == 0)
+        Changes[i].Spaces =
+            std::max(Changes[i].Spaces,
+                     static_cast<int>(Changes[i].Tok->SpacesRequiredBefore));
     }
 
     // This is for function parameters that are split across multiple lines,
     // as mentioned in the ScopeStack comment.
     if (InsideNestedScope && Changes[i].NewlinesBefore > 0) {
       unsigned ScopeStart = ScopeStack.back();
       auto ShouldShiftBeAdded = [&] {
         // Function declaration
if (InsideNestedScope && Changes[i].NewlinesBefore > 0) {
 
       if (ShouldShiftBeAdded())
         Changes[i].Spaces += Shift;
     }
 
     if (ContinuedStringLiteral)
       Changes[i].Spaces += Shift;
 
+    // We should not remove required spaces unless we break the line before.
+    assert(Changes[i].NewlinesBefore > 0 ||
+           Changes[i].Spaces >=
+               static_cast<int>(Changes[i].Tok->SpacesRequiredBefore) ||
+           Changes[i].Tok->is(tok::eof));
+
     Changes[i].StartOfTokenColumn += Shift;
     if (i + 1 != Changes.size())
       Changes[i + 1].PreviousEndOfTokenColumn += Shift;
 
     // If PointerAlignment is PAS_Right, keep *s or &s next to the token
     if (Style.PointerAlignment == FormatStyle::PAS_Right &&
         Changes[i].Spaces != 0) {
       for (int Previous = i - 1;

clang/unittests/Format/FormatTest.cpp

verifyFormat("unsigned int *       a;\n"
                Alignment);
   verifyFormat("Const unsigned int * c;\n"
                "const unsigned int * d;\n"
                "Const unsigned int & e;\n"
                "const unsigned int & f;\n"
                "const unsigned       g;\n"
                "Const unsigned       h;",
                Alignment);
+
+  // See PR46529
+  FormatStyle BracedAlign = getLLVMStyle();
+  BracedAlign.AlignConsecutiveDeclarations = FormatStyle::ACS_Consecutive;
+  verifyFormat("const auto result{[]() {\n"
+               "  const auto something = 1;\n"
+               "  return 2;\n"
+               "}};",
+               BracedAlign);
+  verifyFormat("int foo{[]() {\n"
+               "  int bar{0};\n"
+               "  return 0;\n"
+               "}()};",
+               BracedAlign);
+  BracedAlign.Cpp11BracedListStyle = false;
+  verifyFormat("const auto result{ []() {\n"
+               "  const auto something = 1;\n"
+               "  return 2;\n"
+               "} };",
+               BracedAlign);
+  verifyFormat("int foo{ []() {\n"
+               "  int bar{ 0 };\n"
+               "  return 0;\n"
+               "}() };",
+               BracedAlign);
 }
 
 TEST_F(FormatTest, AlignWithLineBreaks) {
   auto Style = getLLVMStyleWithColumns(120);
 
   EXPECT_EQ(Style.AlignConsecutiveAssignments, FormatStyle::ACS_None);
   EXPECT_EQ(Style.AlignConsecutiveDeclarations, FormatStyle::ACS_None);
   verifyFormat("void foo() {\n"