[clang] check deduction consistency when partial ordering function templates

This makes partial ordering of function templates consistent with
other entities.

Fixes #18291

Author: mizvekov

clang-tools-extra/test/clang-tidy/checkers/bugprone/stringview-nullptr.cpp

@@ -1,4 +1,4 @@
-// RUN: %check_clang_tidy %s bugprone-stringview-nullptr -std=c++17 %t
+// RUN: %check_clang_tidy %s bugprone-stringview-nullptr -std=c++20 %t
 
 namespace std {
 
@@ -30,98 +30,27 @@ class basic_string_view {
   constexpr basic_string_view &operator=(const basic_string_view &) {}
 };
 
-template <typename CharT>
-constexpr bool operator<(basic_string_view<CharT>, basic_string_view<CharT>) {
-  return {};
-}
-template <typename CharT>
-constexpr bool operator<(type_identity_t<basic_string_view<CharT>>,
-                         basic_string_view<CharT>) {
-  return {};
-}
-template <typename CharT>
-constexpr bool operator<(basic_string_view<CharT>,
-                         type_identity_t<basic_string_view<CharT>>) {
-  return {};
-}
-
-template <typename CharT>
-constexpr bool operator<=(basic_string_view<CharT>, basic_string_view<CharT>) {
-  return {};
-}
-template <typename CharT>
-constexpr bool operator<=(type_identity_t<basic_string_view<CharT>>,
-                          basic_string_view<CharT>) {
-  return {};
-}
-template <typename CharT>
-constexpr bool operator<=(basic_string_view<CharT>,
-                          type_identity_t<basic_string_view<CharT>>) {
-  return {};
-}
-
-template <typename CharT>
-constexpr bool operator>(basic_string_view<CharT>, basic_string_view<CharT>) {
-  return {};
-}
-template <typename CharT>
-constexpr bool operator>(type_identity_t<basic_string_view<CharT>>,
-                         basic_string_view<CharT>) {
-  return {};
-}
-template <typename CharT>
-constexpr bool operator>(basic_string_view<CharT>,
-                         type_identity_t<basic_string_view<CharT>>) {
-  return {};
-}
-
-template <typename CharT>
-constexpr bool operator>=(basic_string_view<CharT>, basic_string_view<CharT>) {
-  return {};
-}
-template <typename CharT>
-constexpr bool operator>=(type_identity_t<basic_string_view<CharT>>,
-                          basic_string_view<CharT>) {
-  return {};
-}
-template <typename CharT>
-constexpr bool operator>=(basic_string_view<CharT>,
-                          type_identity_t<basic_string_view<CharT>>) {
-  return {};
-}
+using string_view = basic_string_view<char>;
 
-template <typename CharT>
-constexpr bool operator==(basic_string_view<CharT>, basic_string_view<CharT>) {
+constexpr bool operator<(string_view, string_view) {
   return {};
 }
-template <typename CharT>
-constexpr bool operator==(type_identity_t<basic_string_view<CharT>>,
-                          basic_string_view<CharT>) {
+constexpr bool operator<=(string_view, string_view) {
   return {};
 }
-template <typename CharT>
-constexpr bool operator==(basic_string_view<CharT>,
-                          type_identity_t<basic_string_view<CharT>>) {
+constexpr bool operator>(string_view, string_view) {
   return {};
 }
-
-template <typename CharT>
-constexpr bool operator!=(basic_string_view<CharT>, basic_string_view<CharT>) {
+constexpr bool operator>=(string_view, string_view) {
   return {};
 }
-template <typename CharT>
-constexpr bool operator!=(type_identity_t<basic_string_view<CharT>>,
-                          basic_string_view<CharT>) {
+constexpr bool operator==(string_view, string_view) {
   return {};
 }
-template <typename CharT>
-constexpr bool operator!=(basic_string_view<CharT>,
-                          type_identity_t<basic_string_view<CharT>>) {
+constexpr bool operator!=(string_view, string_view) {
   return {};
 }
 
-using string_view = basic_string_view<char>;
-
 } // namespace std
 
 using SV = std::string_view; // Used in some places for shorter line length

clang/docs/ReleaseNotes.rst

@@ -153,6 +153,8 @@ Bug Fixes to C++ Support
 
 - Fixed a crash when an expression with a dependent ``__typeof__`` type is used as the operand of a unary operator. (#GH97646)
 - Fixed a failed assertion when checking invalid delete operator declaration. (#GH96191)
+- When performing partial ordering of function templates, clang now checks that
+  the deduction was consistent. Fixes (#GH18291).
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^

clang/lib/AST/ExprConstant.cpp

@@ -5346,7 +5346,6 @@ static EvalStmtResult EvaluateStmt(StmtResult &Result, EvalInfo &Info,
     const Expr *RetExpr = cast<ReturnStmt>(S)->getRetValue();
     FullExpressionRAII Scope(Info);
     if (RetExpr && RetExpr->isValueDependent()) {
-      EvaluateDependentExpr(RetExpr, Info);
       // We know we returned, but we don't know what the value is.
       return ESR_Failed;
     }