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[clang] Add FixItHint for designated init order #172959

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[clang] Add FixItHint for designated init order #172959

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bcdb0fd
[clang] Add FixItHint for designated init order
MythreyaK Dec 19, 2025
322f1de
Replace exprs instead of regenerating everything
MythreyaK Dec 19, 2025
b6658b1
fix reordering in derived records, add tests
MythreyaK Dec 19, 2025
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69 changes: 66 additions & 3 deletions clang/lib/Sema/SemaInit.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -31,8 +31,10 @@
#include "clang/Sema/SemaHLSL.h"
#include "clang/Sema/SemaObjC.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/PointerIntPair.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/ErrorHandling.h"
Expand Down Expand Up @@ -3092,6 +3094,66 @@ InitListChecker::CheckDesignatedInitializer(const InitializedEntity &Entity,
PrevField = *FI;
}

const auto GenerateDesignatedInitReorderingFixit =
[&](SemaBase::SemaDiagnosticBuilder &Diags) {
struct ReorderInfo {
int Pos{};
const Expr *InitExpr{};
};

llvm::SmallDenseMap<IdentifierInfo *, int> MemberNameInx{};
llvm::SmallVector<ReorderInfo, 16> ReorderedInitExprs{};

const auto *CxxRecord =
IList->getSemanticForm()->getType()->getAsCXXRecordDecl();

for (const auto &Field : CxxRecord->fields()) {
MemberNameInx[Field->getIdentifier()] = Field->getFieldIndex();
}

for (const auto *Init : IList->inits()) {
if (const auto *DI =
dyn_cast_if_present<DesignatedInitExpr>(Init)) {
// We expect only one Designator
if (DI->size() != 1)
return;

const auto *const FieldName =
DI->getDesignator(0)->getFieldName();
// In case we have an unknown initializer in the source, not in
// the record
if (MemberNameInx.contains(FieldName))
ReorderedInitExprs.emplace_back(
ReorderInfo{MemberNameInx.at(FieldName), Init});
}
}

llvm::sort(ReorderedInitExprs, [](const auto &A, const auto &B) {
return A.Pos < B.Pos;
});

llvm::SmallString<128> FixedInitList{};
SourceManager &SM = SemaRef.getSourceManager();
const LangOptions &LangOpts = SemaRef.getLangOpts();

// if Record is derived, then the first n base-classes are
// initialized first, they cannot be initialized with designated
// init, so skip them
const auto IListInits =
IList->inits().drop_front(CxxRecord->getNumBases());
// loop over each existing expression and apply replacement
for (const auto &[OrigExpr, Repl] :
llvm::zip(IListInits, ReorderedInitExprs)) {
CharSourceRange CharRange = CharSourceRange::getTokenRange(
Repl.InitExpr->getSourceRange());
const auto InitText =
Lexer::getSourceText(CharRange, SM, LangOpts);

Diags << FixItHint::CreateReplacement(OrigExpr->getSourceRange(),
InitText.str());
}
};

if (PrevField &&
PrevField->getFieldIndex() > KnownField->getFieldIndex()) {
SemaRef.Diag(DIE->getInit()->getBeginLoc(),
Expand All @@ -3101,9 +3163,10 @@ InitListChecker::CheckDesignatedInitializer(const InitializedEntity &Entity,
unsigned OldIndex = StructuredIndex - 1;
if (StructuredList && OldIndex <= StructuredList->getNumInits()) {
if (Expr *PrevInit = StructuredList->getInit(OldIndex)) {
SemaRef.Diag(PrevInit->getBeginLoc(),
diag::note_previous_field_init)
<< PrevField << PrevInit->getSourceRange();
auto Diags = SemaRef.Diag(PrevInit->getBeginLoc(),
diag::note_previous_field_init)
<< PrevField << PrevInit->getSourceRange();
GenerateDesignatedInitReorderingFixit(Diags);
}
}
}
Expand Down
58 changes: 57 additions & 1 deletion clang/test/SemaCXX/cxx2a-initializer-aggregates.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@
// RUN: %clang_cc1 -std=c++20 %s -verify=cxx20,expected -Wno-c99-designator -Wno-reorder-init-list -Wno-initializer-overrides
// RUN: %clang_cc1 -std=c++20 %s -verify=cxx20,expected,wmissing,wmissing-designated -Wmissing-field-initializers -Wno-c99-designator -Wno-reorder-init-list -Wno-initializer-overrides
// RUN: %clang_cc1 -std=c++20 %s -verify=cxx20,expected,wmissing -Wmissing-field-initializers -Wno-missing-designated-field-initializers -Wno-c99-designator -Wno-reorder-init-list -Wno-initializer-overrides

// RUN: %clang_cc1 -std=c++20 %s -Wreorder-init-list -fdiagnostics-parseable-fixits 2>&1 | FileCheck %s

namespace class_with_ctor {
struct A { // cxx20-note 6{{candidate}}
Expand Down Expand Up @@ -38,6 +38,8 @@ A a1 = {
.y = 1, // reorder-note {{previous initialization for field 'y' is here}}
.x = 2 // reorder-error {{ISO C++ requires field designators to be specified in declaration order; field 'y' will be initialized after field 'x'}}
};
// CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:3-[[@LINE-3]]:9}:".x = 2"
// CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:3-[[@LINE-3]]:9}:".y = 1"
int arr[3] = {[1] = 5}; // pedantic-error {{array designators are a C99 extension}}
B b = {.a.x = 0}; // pedantic-error {{nested designators are a C99 extension}}
A a2 = {
Expand Down Expand Up @@ -71,6 +73,12 @@ C c = {
.x = 1, // reorder-error {{declaration order}} override-error {{overrides prior initialization}} override-note {{previous}}
.x = 1, // override-error {{overrides prior initialization}}
};
// CHECK: fix-it:"{{.*}}":{[[@LINE-7]]:3-[[@LINE-7]]:9}:".x = 1"
// CHECK: fix-it:"{{.*}}":{[[@LINE-7]]:3-[[@LINE-7]]:9}:".x = 1"
// CHECK: fix-it:"{{.*}}":{[[@LINE-7]]:3-[[@LINE-7]]:9}:".x = 1"
// CHECK: fix-it:"{{.*}}":{[[@LINE-7]]:3-[[@LINE-7]]:9}:".x = 1"
// CHECK: fix-it:"{{.*}}":{[[@LINE-7]]:3-[[@LINE-7]]:9}:".y = 1"
// CHECK: fix-it:"{{.*}}":{[[@LINE-7]]:3-[[@LINE-7]]:9}:".y = 1"

struct Foo { int a, b; };

Expand Down Expand Up @@ -118,6 +126,8 @@ namespace overload_resolution {
void i() {
h({.x = 1, .y = 2});
h({.y = 1, .x = 2}); // reorder-error {{declaration order}} reorder-note {{previous}}
// CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:8-[[@LINE-1]]:14}:".x = 2"
// CHECK: fix-it:"{{.*}}":{[[@LINE-2]]:16-[[@LINE-2]]:22}:".y = 1"
h({.x = 1}); // expected-error {{ambiguous}}
}

Expand Down Expand Up @@ -228,6 +238,16 @@ struct : public A, public B {
.a = 1, // reorder-error {{field 'b' will be initialized after field 'a'}}
};
}
// CHECK: fix-it:"{{.*}}":{[[@LINE-17]]:4-[[@LINE-17]]:8}:".x=2"
// CHECK: fix-it:"{{.*}}":{[[@LINE-15]]:4-[[@LINE-15]]:8}:".y=1"
// CHECK: fix-it:"{{.*}}":{[[@LINE-14]]:4-[[@LINE-14]]:8}:".z=0"
// CHECK: fix-it:"{{.*}}":{[[@LINE-14]]:4-[[@LINE-14]]:8}:".a=4"
// CHECK: fix-it:"{{.*}}":{[[@LINE-14]]:4-[[@LINE-14]]:8}:".b=3"
// CHECK: fix-it:"{{.*}}":{[[@LINE-14]]:5-[[@LINE-14]]:11}:".a = 1"
// CHECK: fix-it:"{{.*}}":{[[@LINE-13]]:5-[[@LINE-13]]:11}:".b = 1"
// CHECK: fix-it:"{{.*}}":{[[@LINE-12]]:5-[[@LINE-12]]:11}:".c = 1"
// CHECK: fix-it:"{{.*}}":{[[@LINE-12]]:5-[[@LINE-12]]:11}:".d = 1"
// CHECK: fix-it:"{{.*}}":{[[@LINE-12]]:5-[[@LINE-12]]:11}:".e = 1"

namespace GH63759 {
struct C {
Expand All @@ -248,3 +268,39 @@ void foo() {
//
}
}

namespace reorder_derived {
struct col {
int r;
int g;
int b;
};

struct point {
float x;
float y;
float z;
};

struct bar : public col, public point {
int z2;
int z1;
};

void foo() {
bar a {
{.b = 1, .g = 2, .r = 3}, // reorder-error {{field 'b' will be initialized after field 'g'}} // reorder-error {{field 'g' will be initialized after field 'r'}} // reorder-note {{previous initialization for field 'b' is here}} // reorder-note {{previous initialization for field 'g' is here}} // pedantic-note {{first non-designated initializer is here}}
{ .z = 1, .y=2, .x = 3 }, // reorder-error {{field 'z' will be initialized after field 'y'}} // reorder-error {{field 'y' will be initialized after field 'x'}} // reorder-note {{previous initialization for field 'z' is here}} // reorder-note {{previous initialization for field 'y' is here}}
.z1 = 1, // pedantic-error {{mixture of designated and non-designated initializers in the same initializer list is a C99 extension}} // reorder-note {{previous initialization for field 'z1' is here}}
.z2 = 2, // reorder-error {{field 'z1' will be initialized after field 'z2'}}
};
}
// CHECK: fix-it:"{{.*}}":{[[@LINE-6]]:6-[[@LINE-6]]:12}:".r = 3"
// CHECK: fix-it:"{{.*}}":{[[@LINE-7]]:14-[[@LINE-7]]:20}:".g = 2"
// CHECK: fix-it:"{{.*}}":{[[@LINE-8]]:22-[[@LINE-8]]:28}:".b = 1"
// CHECK: fix-it:"{{.*}}":{[[@LINE-8]]:15-[[@LINE-8]]:19}:".y=2"
// CHECK: fix-it:"{{.*}}":{[[@LINE-9]]:21-[[@LINE-9]]:28}:".z = 1"
// CHECK: fix-it:"{{.*}}":{[[@LINE-10]]:7-[[@LINE-10]]:13}:".x = 3"
// CHECK: fix-it:"{{.*}}":{[[@LINE-10]]:5-[[@LINE-10]]:12}:".z2 = 2"
// CHECK: fix-it:"{{.*}}":{[[@LINE-10]]:5-[[@LINE-10]]:12}:".z1 = 1"
} // namespace reorder_derived
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