[clang-format] Alignment does not honor ColumnLimit

[HazardyKnusperkeks]

Given the code

LongT foo() const noexcept;
T bar(int arg, int arg2, int arg3,
      int loooooooooooooooong) noexcept;

with AlignConsecutiveDeclarations: true and ColumnLimit: 40 it gets formatted as

LongT foo() const noexcept;
T     bar(int arg, int arg2, int arg3,
          int loooooooooooooooong) noexcept;

which does not fit within the ColumnLimit.

[llvmbot]

@llvm/issue-subscribers-bug

Given the code ```c++ LongT foo() const noexcept; T bar(int arg, int arg2, int arg3, int loooooooooooooooong) noexcept; ``` with `AlignConsecutiveDeclarations: true` and `ColumnLimit: 40` it gets formatted as ```c++ LongT foo() const noexcept; T bar(int arg, int arg2, int arg3, int loooooooooooooooong) noexcept; ``` which does not fit within the `ColumnLimit`.

[llvmbot]

@llvm/issue-subscribers-clang-format

Given the code ```c++ LongT foo() const noexcept; T bar(int arg, int arg2, int arg3, int loooooooooooooooong) noexcept; ``` with `AlignConsecutiveDeclarations: true` and `ColumnLimit: 40` it gets formatted as ```c++ LongT foo() const noexcept; T bar(int arg, int arg2, int arg3, int loooooooooooooooong) noexcept; ``` which does not fit within the `ColumnLimit`.

[HazardyKnusperkeks]

Okay, I know that we need to check the next line(s) for the width here:

llvm-project/clang/lib/Format/WhitespaceManager.cpp

Lines 647 to 656 in afe957e

	for (unsigned j = i + 1; j != e && Changes[j].NewlinesBefore == 0; ++j) {
	ChangeWidthRight += Changes[j].Spaces;
	// Changes are generally 1:1 with the tokens, but a change could also be
	// inside of a token, in which case it's counted more than once: once for
	// the whitespace surrounding the token (!IsInsideToken) and once for
	// each whitespace change within it (IsInsideToken).
	// Therefore, changes inside of a token should only count the space.
	if (!Changes[j].IsInsideToken)
	ChangeWidthRight += Changes[j].TokenLength;
	}

But no idea how to detect if the next line belongs to the statement, any idea @owenca @mydeveloperday ?

[owenca]

What's the expected/preferred format for the example at the top?

[HazardyKnusperkeks]

I never thought about what I prefer. But consistently it would be the given code. The alignment does not add line breaks, it just doesn't align if it doesn't fit. Easily achievable when the first line of bar would be longer (and thus not fit in the ColumnLimit when aligned.

This is a corner case which I never saw before, and I have basically all alignment options activated.