ychen added a comment.
@mizvekov Thanks for taking a look.
================
Comment at: clang/lib/Sema/SemaTemplateDeduction.cpp:5195-5196
+ for (int i = 0, e = std::min(NumParams1, NumParams2); i < e; ++i) {
+ QualType T1 = FD1->getParamDecl(i)->getType().getDesugaredType(Context);
+ QualType T2 = FD2->getParamDecl(i)->getType().getDesugaredType(Context);
+ auto *TST1 = dyn_cast<TemplateSpecializationType>(T1);
----------------
mizvekov wrote:
> This should work, as all the properties you are testing below are present on
> the canonical type.
Gotta admit that I was confused by `DesugaredType` and `CanonicalType`. But
since you pointed it out, I could see the differences now. The `CanonicalType`
could be sugared, and desugaring is not necessary here. Thanks.
================
Comment at: clang/lib/Sema/SemaTemplateDeduction.cpp:5455-5456
if (!ClangABICompat15) {
- // Consider this a fix for CWG1432. Similar to the fix for CWG1395.
auto *TST1 = T1->castAs<TemplateSpecializationType>();
auto *TST2 = T2->castAs<TemplateSpecializationType>();
+ const TemplateArgument &TA1 = TST1->template_arguments().back();
----------------
mizvekov wrote:
> This is a bug, T1 and T2 are not in general canonical types for this
> function, and this castAs can pick up an alias template, and these should
> never participate in deduction.
>
> (Also, can you please add a test for that?)
>
> You should not need to keep sugar here, everything being tested below is
> present on the canonical type, so this is simple to solve, as suggested.
I see. I'll add a test.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D133683/new/
https://reviews.llvm.org/D133683
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