PR0091R3: Implement parsing support for using templates as types.

This change adds a new type node, DeducedTemplateSpecializationType, to
represent a type template name that has been used as a type. This is modeled
around AutoType, and shares a common base class for representing a deduced
placeholder type.

We allow deduced class template types in a few more places than the standard
does: in conditions and for-range-declarators, and in new-type-ids. This is
consistent with GCC and with discussion on the core reflector. This patch
does not yet support deduced class template types being named in typename
specifiers.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@293207 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 15 insertions, 10 deletions

diff --git a/lib/Parse/ParseDecl.cpp b/lib/Parse/ParseDecl.cpp
index 255f27dbfb..6da61c689e 100644
--- a/lib/Parse/ParseDecl.cpp
+++ b/lib/Parse/ParseDecl.cpp
@@ -2884,7 +2884,8 @@ void Parser::ParseDeclarationSpecifiers(DeclSpec &DS,
           Actions.getTypeName(*Next.getIdentifierInfo(), Next.getLocation(),
                               getCurScope(), &SS, false, false, nullptr,
                               /*IsCtorOrDtorName=*/false,
-                              /*NonTrivialSourceInfo=*/true);
+                              /*WantNonTrivialSourceInfo=*/true,
+                              isClassTemplateDeductionContext(DSContext));
 
       // If the referenced identifier is not a type, then this declspec is
       // erroneous: We already checked about that it has no type specifier, and
@@ -2998,9 +2999,10 @@ void Parser::ParseDeclarationSpecifiers(DeclSpec &DS,
         continue;
       }
 
-      ParsedType TypeRep =
-        Actions.getTypeName(*Tok.getIdentifierInfo(),
-                            Tok.getLocation(), getCurScope());
+      ParsedType TypeRep = Actions.getTypeName(
+          *Tok.getIdentifierInfo(), Tok.getLocation(), getCurScope(), nullptr,
+          false, false, nullptr, false, false,
+          isClassTemplateDeductionContext(DSContext));
 
       // If this is not a typedef name, don't parse it as part of the declspec,
       // it must be an implicit int or an error.
diff --git a/lib/Parse/ParseDeclCXX.cpp b/lib/Parse/ParseDeclCXX.cpp
index 3f1fe7e06f..ca5a251b35 100644
--- a/lib/Parse/ParseDeclCXX.cpp
+++ b/lib/Parse/ParseDeclCXX.cpp
@@ -1144,10 +1144,11 @@ TypeResult Parser::ParseBaseTypeSpecifier(SourceLocation &BaseLoc,
 
   // We have an identifier; check whether it is actually a type.
   IdentifierInfo *CorrectedII = nullptr;
-  ParsedType Type =
-      Actions.getTypeName(*Id, IdLoc, getCurScope(), &SS, true, false, nullptr,
-                          /*IsCtorOrDtorName=*/false,
-                          /*NonTrivialTypeSourceInfo=*/true, &CorrectedII);
+  ParsedType Type = Actions.getTypeName(
+      *Id, IdLoc, getCurScope(), &SS, true, false, nullptr,
+      /*IsCtorOrDtorName=*/false,
+      /*NonTrivialTypeSourceInfo=*/true,
+      /*IsClassTemplateDeductionContext*/ false, &CorrectedII);
   if (!Type) {
     Diag(IdLoc, diag::err_expected_class_name);
     return true;
diff --git a/lib/Parse/ParseExprCXX.cpp b/lib/Parse/ParseExprCXX.cpp
index 383986470d..cfda2cddec 100644
--- a/lib/Parse/ParseExprCXX.cpp
+++ b/lib/Parse/ParseExprCXX.cpp
@@ -1639,9 +1639,10 @@ ExprResult Parser::ParseCXXThis() {
 ///         typename-specifier '(' expression-list[opt] ')'
 /// [C++0x] typename-specifier braced-init-list
 ///
+/// In C++1z onwards, the type specifier can also be a template-name.
 ExprResult
 Parser::ParseCXXTypeConstructExpression(const DeclSpec &DS) {
-  Declarator DeclaratorInfo(DS, Declarator::TypeNameContext);
+  Declarator DeclaratorInfo(DS, Declarator::FunctionalCastContext);
   ParsedType TypeRep = Actions.ActOnTypeName(getCurScope(), DeclaratorInfo).get();
 
   assert((Tok.is(tok::l_paren) ||
diff --git a/lib/Parse/Parser.cpp b/lib/Parse/Parser.cpp
index 2f8ee0c068..8713bb2c23 100644
--- a/lib/Parse/Parser.cpp
+++ b/lib/Parse/Parser.cpp
@@ -1743,7 +1743,8 @@ bool Parser::TryAnnotateTypeOrScopeTokenAfterScopeSpec(CXXScopeSpec &SS,
             *Tok.getIdentifierInfo(), Tok.getLocation(), getCurScope(), &SS,
             false, NextToken().is(tok::period), nullptr,
             /*IsCtorOrDtorName=*/false,
-            /*NonTrivialTypeSourceInfo*/ true)) {
+            /*NonTrivialTypeSourceInfo*/ true,
+            /*IsClassTemplateDeductionContext*/GreaterThanIsOperator)) {
       SourceLocation BeginLoc = Tok.getLocation();
       if (SS.isNotEmpty()) // it was a C++ qualified type name.
         BeginLoc = SS.getBeginLoc();