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Emit a diagnostic warning about parsing ambiguity in a conjunction #55

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Emit a diagnostic warning about parsing ambiguity in a conjunction #55

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378e907
feat: first version of implementation
BaLiKfromUA May 27, 2024
53c7d38
test: add basic test for parsing
BaLiKfromUA May 28, 2024
98b0a59
minor refactoring
BaLiKfromUA May 28, 2024
32c3567
fix: add suppressing of introduced warning
BaLiKfromUA May 30, 2024
99e6528
feat: add warning for parsing of '&' token in reflection expr
BaLiKfromUA May 30, 2024
44b62f0
style: revert some changes
BaLiKfromUA May 30, 2024
a13d5e8
style: remove tabs
BaLiKfromUA May 30, 2024
6772510
style: remove tabs
BaLiKfromUA May 30, 2024
7be17b0
refactor: improve wording in warning
BaLiKfromUA May 31, 2024
bfdfdd6
refactor: replace hardcoded lines in tests
BaLiKfromUA Jun 9, 2024
a736536
fix: false positive warning during parsing rvalue of type `meta::info`
BaLiKfromUA Jun 9, 2024
3554cdb
refactor: rename and move test to Reflection folder
BaLiKfromUA Jun 9, 2024
af2a8c1
refactor: change wording in warning
BaLiKfromUA Jun 9, 2024
5bb406e
fix typo
BaLiKfromUA Jun 9, 2024
a2aead4
test: add more test cases
BaLiKfromUA Jun 9, 2024
07bba7b
test: add more test cases
BaLiKfromUA Jun 11, 2024
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3 changes: 3 additions & 0 deletions clang/include/clang/Basic/DiagnosticGroups.td
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Expand Up @@ -1532,3 +1532,6 @@ def BitIntExtension : DiagGroup<"bit-int-extension">;

// Warnings about misuse of ExtractAPI options.
def ExtractAPIMisuse : DiagGroup<"extractapi-misuse">;

// Warning related to reflection
def ReflExprParsingAmbiguity : DiagGroup<"reflect-parsing-ambiguity">;
6 changes: 6 additions & 0 deletions clang/include/clang/Basic/DiagnosticParseKinds.td
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Expand Up @@ -1713,6 +1713,12 @@ let CategoryName = "Reflection Issue" in {
def err_cannot_reflect_entity : Error<"cannot reflect entity">;
def err_expansion_statements_disabled : Error<
"'template for' statements are not enabled; use '-fexpansion-statements'">;

def warn_parsing_ambiguity_in_refl_expression_with_reference_types : Warning <
"given expression may be misinterpreted due to '%0 %1'"
" type parsing logic. did you mean '... (^%0) %1 ...'?"
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nit: maybe something like:

token '&&' binds left to the type 'int &&'; did you mean '(^int) &&'?

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Changed. But I still cannot get name of type :(
So message looks like this: token '&' binds left to type 'T &'; did you mean '(^T) &'?

I checked similar places in a code to get an idea where to get type name but in all methods names are empty for my tests.

>,
InGroup<ReflExprParsingAmbiguity>;
}

let CategoryName = "Generics Issue" in {
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15 changes: 15 additions & 0 deletions clang/lib/Parse/ParseDecl.cpp
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Expand Up @@ -6750,6 +6750,21 @@ void Parser::ParseDeclaratorInternal(Declarator &D,
// Is a reference
DeclSpec DS(AttrFactory);

// Complain about parsing ambiguity of parsing reference types
// inside expressions with reflection in C++2x
if (D.getContext() == DeclaratorContext::ReflectOperator &&
!Tok.isOneOf(tok::r_paren, tok::semi)) {
// parser already consumed '^' token before setting this context
assert((Kind == tok::ampamp || Kind == tok::amp) &&
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Unfortunately, there are a lot more cases here. I'm not sure this approach will work (although it might - not really sure one way or the other).

r == ^int& ? 1 : 0
condition ? ^int& : ^int;
^int&(*)(bool)
^int& != r
^int& == r
constexpr auto r {^int&};

In addition to those, in the presence of some user-defined

consteval result_type operator???(std::meta::info R, MyStupidClass);

You could have ^int& + o, along with: -, *, /, %, ], |, || <=, >=, >.

Those are all the cases I can think of off the top of my head, but I may have forgotten some.

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thank you! gonna think more how to address it

"expected '&' or '&&'");
Diag(Loc,
diag::warn_parsing_ambiguity_in_refl_expression_with_reference_types)
<< (D.hasName()
? Actions.GetNameForDeclarator(D).getName().getAsString()
: "T")
<< tok::getPunctuatorSpelling(Kind);
}

// Complain about rvalue references in C++03, but then go on and build
// the declarator.
if (Kind == tok::ampamp)
Expand Down
42 changes: 42 additions & 0 deletions clang/test/Reflection/ambig-reflect-expr-parsing.cpp
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@@ -0,0 +1,42 @@
//===----------------------------------------------------------------------===//
//
// Copyright 2024 Bloomberg Finance L.P.
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// RUN: %clang_cc1 -std=c++26 -freflection -Wno-parentheses -verify %s


enum MyEnum { x, y, e = -1, f, z = 99 };

void func(MyEnum && x) { // ok
MyEnum value{};
MyEnum& ref = value;

constexpr auto reflValue = ^value;

constexpr bool test_comparison_0 = reflValue != (^MyEnum) && true; // ok
constexpr bool test_comparison_1 = (reflValue != (^MyEnum) && true); // ok

constexpr bool test_comparison_2 = ^MyEnum != (^MyEnum) && true; // ok
constexpr bool test_comparison_3 = (^MyEnum != (^MyEnum) && true); // ok

constexpr bool test_comparison_4 = (reflValue != (^MyEnum) & true); // ok

constexpr bool test_comparison_5 = reflValue != ^MyEnum && true;
// expected-warning@-1 {{given expression may be misinterpreted due to 'T &&' type parsing logic. did you mean '... (^T) && ...'?}}
// expected-error@-2 {{expected ';' at end of declaration}}
constexpr bool test_comparison_6 = reflValue != ^MyEnum & true;
// expected-warning@-1 {{given expression may be misinterpreted due to 'T &' type parsing logic. did you mean '... (^T) & ...'?}}
// expected-error@-2 {{expected ';' at end of declaration}}

constexpr auto test_ref_type_0 = ^int &; // ok
constexpr auto test_ref_type_1 = ^int &&; // ok
constexpr auto test_ref_type_2 = (^int &); // ok
constexpr auto test_ref_type_3 = (^int &&); // ok
}