2 files changed, 24 insertions, 4 deletions
diff --git a/clang/include/clang/Basic/DiagnosticParseKinds.td b/clang/include/clang/Basic/DiagnosticParseKinds.td
index cc6a74ac3e6..41f788e7d9b 100644
--- a/clang/include/clang/Basic/DiagnosticParseKinds.td
+++ b/clang/include/clang/Basic/DiagnosticParseKinds.td
@@ -33,10 +33,6 @@ def err_asm_goto_cannot_have_output : Error<
 
 let CategoryName = "Parse Issue" in {
 
-def warn_cxx2a_compat_explicit_bool : Warning<
-  "this expression will be parsed as explicit(bool) in C++2a">,
-  InGroup<CXX2aCompat>, DefaultIgnore;
-
 def ext_empty_translation_unit : Extension<
   "ISO C requires a translation unit to contain at least one declaration">,
   InGroup<DiagGroup<"empty-translation-unit">>;
@@ -684,6 +680,15 @@ def err_ms_property_expected_comma_or_rparen : Error<
 def err_ms_property_initializer : Error<
   "property declaration cannot have an in-class initializer">;
 
+def warn_cxx2a_compat_explicit_bool : Warning<
+  "this expression will be parsed as explicit(bool) in C++2a">,
+  InGroup<CXX2aCompat>, DefaultIgnore;
+def warn_cxx17_compat_explicit_bool : Warning<
+  "explicit(bool) is incompatible with C++ standards before C++2a">,
+  InGroup<CXXPre2aCompat>, DefaultIgnore;
+def ext_explicit_bool : ExtWarn<"explicit(bool) is a C++2a extension">,
+  InGroup<CXX2a>;
+
 /// C++ Templates
 def err_expected_template : Error<"expected template">;
 def err_unknown_template_name : Error<
diff --git a/clang/include/clang/Parse/Parser.h b/clang/include/clang/Parse/Parser.h
index e320c964781..b7bed471399 100644
--- a/clang/include/clang/Parse/Parser.h
+++ b/clang/include/clang/Parse/Parser.h
@@ -806,6 +806,16 @@ public:
                                                  bool IsNewScope);
   bool TryAnnotateCXXScopeToken(bool EnteringContext = false);
 
+  bool MightBeCXXScopeToken() {
+    return Tok.is(tok::identifier) || Tok.is(tok::coloncolon) ||
+           (Tok.is(tok::annot_template_id) &&
+            NextToken().is(tok::coloncolon)) ||
+           Tok.is(tok::kw_decltype) || Tok.is(tok::kw___super);
+  }
+  bool TryAnnotateOptionalCXXScopeToken(bool EnteringContext = false) {
+    return MightBeCXXScopeToken() && TryAnnotateCXXScopeToken(EnteringContext);
+  }
+
 private:
   enum AnnotatedNameKind {
     /// Annotation has failed and emitted an error.
@@ -2395,6 +2405,11 @@ private:
   /// rather than a less-than expression.
   TPResult isTemplateArgumentList(unsigned TokensToSkip);
 
+  /// Determine whether an '(' after an 'explicit' keyword is part of a C++20
+  /// 'explicit(bool)' declaration, in earlier language modes where that is an
+  /// extension.
+  TPResult isExplicitBool();
+
   /// Determine whether an identifier has been tentatively declared as a
   /// non-type. Such tentative declarations should not be found to name a type
   /// during a tentative parse, but also should not be annotated as a non-type.