[C++20] add Basic consteval specifier

Summary:
this revision adds Lexing, Parsing and Basic Semantic for the consteval specifier as specified by http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1073r3.html

with this patch, the consteval specifier is treated as constexpr but can only be applied to function declaration.

Changes:
 - add the consteval keyword.
 - add parsing of consteval specifier for normal declarations and lambdas expressions.
 - add the whether a declaration is constexpr is now represented by and enum everywhere except for variable because they can't be consteval.
 - adapt diagnostic about constexpr to print constexpr or consteval depending on the case.
 - add tests for basic semantic.

Reviewers: rsmith, martong, shafik

Reviewed By: rsmith

Subscribers: eraman, efriedma, rnkovacs, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D61790

llvm-svn: 363362

1 files changed, 5 insertions, 2 deletions

diff --git a/clang/lib/AST/TextNodeDumper.cpp b/clang/lib/AST/TextNodeDumper.cpp
index 06388c28d96..1998cfaec04 100644
--- a/clang/lib/AST/TextNodeDumper.cpp
+++ b/clang/lib/AST/TextNodeDumper.cpp
@@ -255,9 +255,12 @@ void TextNodeDumper::Visit(const Decl *D) {
 
   if (D->isInvalidDecl())
     OS << " invalid";
-  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D))
-    if (FD->isConstexpr())
+  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
+    if (FD->isConstexprSpecified())
       OS << " constexpr";
+    if (FD->isConsteval())
+      OS << " consteval";
+  }
 
   if (!isa<FunctionDecl>(*D)) {
     const auto *MD = dyn_cast<ObjCMethodDecl>(D);