Diagnostic is not specific enough when when scoped enumeration requires a explicit conversion for binary operations

[chandlerc]

Bugzilla Link	23891
Version	unspecified
OS	All
CC	@DougGregor,@Weverything

Extended Description

I just got the worst syntax error message I've seen in a long time:

In file included from ../lib/CodeGen/PostRASchedulerList.cpp:27:
../include/llvm/Analysis/AliasAnalysis.h:129:57: error: invalid operands to binary expression ('llvm::FunctionModRefLocation' and 'llvm::ModRefInfo')
  DoesNotAccessMemory = FunctionModRefLocation::Nowhere | ModRefInfo::NoModRef,
                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~
../include/llvm/Analysis/AliasAnalysis.h:137:48: error: invalid operands to binary expression ('llvm::FunctionModRefLocation' and 'llvm::ModRefInfo')
      FunctionModRefLocation::ArgumentPointees | ModRefInfo::Ref,
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~
../include/llvm/Analysis/AliasAnalysis.h:145:48: error: invalid operands to binary expression ('llvm::FunctionModRefLocation' and 'llvm::ModRefInfo')
      FunctionModRefLocation::ArgumentPointees | ModRefInfo::ModRef,
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~
../include/llvm/Analysis/AliasAnalysis.h:153:54: error: invalid operands to binary expression ('llvm::FunctionModRefLocation' and 'llvm::ModRefInfo')
  OnlyReadsMemory = FunctionModRefLocation::Anywhere | ModRefInfo::Ref,
                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~

The bug is that these are scoped enumerations and so there is no | operator (it would require an implicit conversion to int). But the error message literally tells me nothing other than that there is an error. =[ =[ =[

[Weverything]

There's three cases to consider.

1. Two scoped enumeration operands
2. One scoped enumeration and one arithmetic operand
3. One scoped enumeration and one other type of operand

The first two are the important cases, since if the scoped enum is treated as the underlying integer type, then binary operation would work. We could possibly add a fix-it hint to the scoped enumeration to static_cast it to the underlying type.

[Endilll]

Clang 21.0 emits the same diagnostic: https://godbolt.org/z/aT4eKfh3f

[shafik]

Other implementations are not much better: https://godbolt.org/z/Tz6cMq35v

[shafik]

AFAICT we are hitting this diagnostic in Sema::CheckBitwiseOperands:

llvm-project/clang/lib/Sema/SemaExpr.cpp

Lines 13313 to 13315 in c215318

	if (!compType.isNull() && compType->isIntegralOrUnscopedEnumerationType())
	return compType;
	return InvalidOperands(Loc, LHS, RHS);

This diagnostic though should also apply for other binary operations so maybe we should specialize InvalidOperands(...) but we are using it pretty generically and special casing scoped enumerations here may not totally make sense for all the use cases. So it might require some thoughtfulness to make sure the fix does not introduce unintended issues.

[llvmbot]

Hi!

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[llvmbot]

@llvm/issue-subscribers-good-first-issue

Author: Chandler Carruth (chandlerc)

| | | | --- | --- | | Bugzilla Link | [23891](https://llvm.org/bz23891) | | Version | unspecified | | OS | All | | CC | @DougGregor,@Weverything |

Extended Description

I just got the worst syntax error message I've seen in a long time:

In file included from ../lib/CodeGen/PostRASchedulerList.cpp:27:
../include/llvm/Analysis/AliasAnalysis.h:129:57: error: invalid operands to binary expression ('llvm::FunctionModRefLocation' and 'llvm::ModRefInfo')
  DoesNotAccessMemory = FunctionModRefLocation::Nowhere | ModRefInfo::NoModRef,
                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~
../include/llvm/Analysis/AliasAnalysis.h:137:48: error: invalid operands to binary expression ('llvm::FunctionModRefLocation' and 'llvm::ModRefInfo')
      FunctionModRefLocation::ArgumentPointees | ModRefInfo::Ref,
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~
../include/llvm/Analysis/AliasAnalysis.h:145:48: error: invalid operands to binary expression ('llvm::FunctionModRefLocation' and 'llvm::ModRefInfo')
      FunctionModRefLocation::ArgumentPointees | ModRefInfo::ModRef,
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~
../include/llvm/Analysis/AliasAnalysis.h:153:54: error: invalid operands to binary expression ('llvm::FunctionModRefLocation' and 'llvm::ModRefInfo')
  OnlyReadsMemory = FunctionModRefLocation::Anywhere | ModRefInfo::Ref,
                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~

The bug is that these are scoped enumerations and so there is no | operator (it would require an implicit conversion to int). But the error message literally tells me nothing other than that there is an error. =[ =[ =[

[tinnamchoi]

I'm working on this, can someone assign it to me?

[shafik]

I'm working on this, can someone assign it to me?

We are assigning after a PR is posted.