Don't expose __is_deducible trait.

Author: hokein

clang/docs/ReleaseNotes.rst

@@ -168,10 +168,6 @@ C++20 Feature Support
   to update the ``__cpp_concepts`` macro to `202002L`. This enables
   ``<expected>`` from libstdc++ to work correctly with Clang.
 
-- Implemented the `__is_deducible` builtin to check if the template arguments of
-  a class/alias template can be deduced from a specific type,
-  [over.match.class.deduct]p4.
-
 C++23 Feature Support
 ^^^^^^^^^^^^^^^^^^^^^
 

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -9156,10 +9156,6 @@ def note_inequality_comparison_to_or_assign : Note<
 def err_incomplete_type_used_in_type_trait_expr : Error<
   "incomplete type %0 used in type trait expression">;
 
-def err_deducible_non_class_or_alias_types : Error<
-   "%0 is not a class or alias template; __is_deducible only supports class or "
-    "alias templates">;
-
 // C++20 constinit and require_constant_initialization attribute
 def warn_cxx20_compat_constinit : Warning<
   "'constinit' specifier is incompatible with C++ standards before C++20">,

clang/include/clang/Basic/TokenKinds.def

@@ -537,7 +537,6 @@ TYPE_TRAIT_1(__is_referenceable, IsReferenceable, KEYCXX)
 TYPE_TRAIT_1(__can_pass_in_regs, CanPassInRegs, KEYCXX)
 TYPE_TRAIT_2(__reference_binds_to_temporary, ReferenceBindsToTemporary, KEYCXX)
 TYPE_TRAIT_2(__reference_constructs_from_temporary, ReferenceConstructsFromTemporary, KEYCXX)
-TYPE_TRAIT_2(__is_deducible, IsDeducible, KEYCXX)
 
 // Embarcadero Expression Traits
 EXPRESSION_TRAIT(__is_lvalue_expr, IsLValueExpr, KEYCXX)

clang/include/clang/Basic/TypeTraits.h

@@ -26,8 +26,13 @@ enum TypeTrait {
 #include "clang/Basic/TokenKinds.def"
   ,
 #define TYPE_TRAIT_2(Spelling, Name, Key) BTT_##Name,
+  // IsDeducible is only used internally by clang for CTAD implementation and
+  // is not exposed to users.
+  TYPE_TRAIT_2(/**/, IsDeducible, KEYCXX)
 #include "clang/Basic/TokenKinds.def"
-  BTT_Last = UTT_Last // BTT_Last == last BTT_XX in the enum.
+  // +1 for the IsDeducible enumerator.
+  BTT_Last = UTT_Last + 1 // BTT_Last == last BTT_XX in the enum.
+
 #define TYPE_TRAIT_2(Spelling, Name, Key) +1
 #include "clang/Basic/TokenKinds.def"
   ,

clang/lib/Basic/TypeTraits.cpp

@@ -19,6 +19,9 @@ static constexpr const char *TypeTraitNames[] = {
 #define TYPE_TRAIT_1(Spelling, Name, Key) #Name,
 #include "clang/Basic/TokenKinds.def"
 #define TYPE_TRAIT_2(Spelling, Name, Key) #Name,
+    // IsDeducible is only used internally by clang for CTAD implementation and
+    // is not exposed to users.
+    TYPE_TRAIT_2(/**/, IsDeducible, KEYCXX)
 #include "clang/Basic/TokenKinds.def"
 #define TYPE_TRAIT_N(Spelling, Name, Key) #Name,
 #include "clang/Basic/TokenKinds.def"
@@ -28,6 +31,9 @@ static constexpr const char *TypeTraitSpellings[] = {
 #define TYPE_TRAIT_1(Spelling, Name, Key) #Spelling,
 #include "clang/Basic/TokenKinds.def"
 #define TYPE_TRAIT_2(Spelling, Name, Key) #Spelling,
+    // __is_deducible is only used internally by clang for CTAD implementation
+    // and is not exposed to users.
+    TYPE_TRAIT_2(__is_deducible, /**/, KEYCXX)
 #include "clang/Basic/TokenKinds.def"
 #define TYPE_TRAIT_N(Spelling, Name, Key) #Spelling,
 #include "clang/Basic/TokenKinds.def"
@@ -59,6 +65,9 @@ static constexpr const unsigned TypeTraitArities[] = {
 #define TYPE_TRAIT_1(Spelling, Name, Key) 1,
 #include "clang/Basic/TokenKinds.def"
 #define TYPE_TRAIT_2(Spelling, Name, Key) 2,
+    // IsDeducible is only used internally by clang for CTAD implementation and
+    // is not exposed to users.
+    TYPE_TRAIT_2(/**/, IsDeducible, KEYCXX)
 #include "clang/Basic/TokenKinds.def"
 #define TYPE_TRAIT_N(Spelling, Name, Key) 0,
 #include "clang/Basic/TokenKinds.def"

clang/lib/Parse/ParseExprCXX.cpp

@@ -3906,18 +3906,14 @@ ExprResult Parser::ParseTypeTrait() {
   BalancedDelimiterTracker Parens(*this, tok::l_paren);
   if (Parens.expectAndConsume())
     return ExprError();
-  TypeTrait TTKind = TypeTraitFromTokKind(Kind);
+
   SmallVector<ParsedType, 2> Args;
   do {
     // Parse the next type.
-    TypeResult Ty = ParseTypeName(
-        /*SourceRange=*/nullptr,
-        getLangOpts().CPlusPlus
-            // For __is_deducible type trait, the first argument is a template
-            // specification type without template argument lists.
-            ? (TTKind == BTT_IsDeducible ? DeclaratorContext::TemplateArg
-                                         : DeclaratorContext::TemplateTypeArg)
-            : DeclaratorContext::TypeName);
+    TypeResult Ty = ParseTypeName(/*SourceRange=*/nullptr,
+                                  getLangOpts().CPlusPlus
+                                      ? DeclaratorContext::TemplateTypeArg
+                                      : DeclaratorContext::TypeName);
     if (Ty.isInvalid()) {
       Parens.skipToEnd();
       return ExprError();
@@ -3941,7 +3937,7 @@ ExprResult Parser::ParseTypeTrait() {
 
   SourceLocation EndLoc = Parens.getCloseLocation();
 
-  return Actions.ActOnTypeTrait(TTKind, Loc, Args, EndLoc);
+  return Actions.ActOnTypeTrait(TypeTraitFromTokKind(Kind), Loc, Args, EndLoc);
 }
 
 /// ParseArrayTypeTrait - Parse the built-in array type-trait

clang/lib/Sema/SemaExprCXX.cpp

@@ -6125,9 +6125,7 @@ static bool EvaluateBinaryTypeTrait(Sema &Self, TypeTrait BTT, const TypeSourceI
                  TSTToBeDeduced->getTemplateName().getAsTemplateDecl(), RhsT,
                  Info) == TemplateDeductionResult::Success;
     }
-    Self.Diag(Lhs->getTypeLoc().getBeginLoc(),
-              diag::err_deducible_non_class_or_alias_types)
-        << LhsT << Lhs->getTypeLoc().getSourceRange();
+    assert("Expect to see DeducedTemplateSpecializationType!");
     return false;
   }
     default: llvm_unreachable("not a BTT");

clang/test/SemaCXX/type-traits-is-deducible.cpp

@@ -282,7 +282,9 @@ using AFoo = Foo<G<U>>;
 // CHECK-NEXT: | |   `-ImplicitCastExpr {{.*}}
 // CHECK-NEXT: | |     `-IntegerLiteral {{.*}}
 // CHECK-NEXT: | `-TypeTraitExpr {{.*}} 'bool' __is_deducible
-// CHECK-NEXT: |-CXXDeductionGuideDecl {{.*}} implicit <deduction guide for AFoo> 'auto (G<type-parameter-0-0>) -> Foo<G<type-parameter-0-0>>'
+// CHECK-NEXT: |   |-DeducedTemplateSpecializationType {{.*}} 'AFoo' dependent
+// CHECK-NEXT: |   `-TemplateSpecializationType {{.*}} 'Foo<G<type-parameter-0-0>>' dependent Foo
+// CHECK:      |-CXXDeductionGuideDecl {{.*}} implicit <deduction guide for AFoo> 'auto (G<type-parameter-0-0>) -> Foo<G<type-parameter-0-0>>'
 // CHECK-NEXT: | `-ParmVarDecl {{.*}} 'G<type-parameter-0-0>'
 // CHECK-NEXT: `-CXXDeductionGuideDecl {{.*}} implicit used <deduction guide for AFoo> 'auto (G<int>) -> Foo<G<int>>' implicit_instantiation
 // CHECK-NEXT:   |-TemplateArgument type 'int'

clang/test/SemaTemplate/deduction-guide.cpp

@@ -875,7 +875,13 @@ <h2 id="cxx20">C++20 implementation status</h2>
     <tr>
       <td>Class template argument deduction for alias templates</td>
       <td><a href="https://wg21.link/p1814r0">P1814R0</a></td>
-      <td class="partial" align="center">Clang 19 (Partial)</td>
+      <td class="partial" align="center">
+        <details>
+          <summary>Clang 19 (Partial)</summary>
+          This feature has been initially completed, but the feature macro
+          __cpp_deduction_guides has not been updated.
+        </details>
+      </td>
     </tr>
     <tr>
       <td>Permit conversions to arrays of unknown bound</td>