Fix regression introduced by r279164: only pass definitions as the PatternDef

to DiagnoseUninstantiableTemplate, teach hasVisibleDefinition to correctly
determine whether a function definition is visible, and mark both the function
and the template as visible when merging function template definitions to
provide hasVisibleDefinition with the relevant information.

The change to always pass the right declaration as the PatternDef to
DiagnoseUninstantiableTemplate also caused those checks to happen before other
diagnostics in InstantiateFunctionDefinition, giving worse diagnostics for the
same situations, so I sunk the relevant diagnostics into
DiagnoseUninstantiableTemplate. Those parts of this patch are based on changes
in reviews.llvm.org/D23492 by Vassil Vassilev.


This reinstates r279486, reverted in r279500, with a fix to
DiagnoseUninstantiableTemplate to only mark uninstantiable explicit
instantiation declarations as invalid if we actually diagnosed them. (When we
trigger an explicit instantiation of a class member from an explicit
instantiation declaration for the class, it's OK if there is no corresponding
definition and we certainly don't want to mark the member invalid in that
case.) This previously caused a build failure during bootstrap.

llvm-svn: 279557

7 files changed, 67 insertions, 64 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index ca4de55fb51..9122030e16d 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -11274,9 +11274,8 @@ Sema::CheckForFunctionRedefinition(FunctionDecl *FD,
     SkipBody->ShouldSkip = true;
     if (auto *TD = Definition->getDescribedFunctionTemplate())
       makeMergedDefinitionVisible(TD, FD->getLocation());
-    else
-      makeMergedDefinitionVisible(const_cast<FunctionDecl*>(Definition),
-                                  FD->getLocation());
+    makeMergedDefinitionVisible(const_cast<FunctionDecl*>(Definition),
+                                FD->getLocation());
     return;
   }
 
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index ede1c5bcc64..ea0357a3359 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -483,15 +483,13 @@ bool Sema::DiagnoseUninstantiableTemplate(SourceLocation PointOfInstantiation,
     return false;
   }
 
+  if (!Complain || (PatternDef && PatternDef->isInvalidDecl()))
+    return true;
 
   QualType InstantiationTy;
   if (TagDecl *TD = dyn_cast<TagDecl>(Instantiation))
     InstantiationTy = Context.getTypeDeclType(TD);
-  else
-    InstantiationTy = cast<FunctionDecl>(Instantiation)->getType();
-  if (!Complain || (PatternDef && PatternDef->isInvalidDecl())) {
-    // Say nothing
-  } else if (PatternDef) {
+  if (PatternDef) {
     Diag(PointOfInstantiation,
          diag::err_template_instantiate_within_definition)
       << (TSK != TSK_ImplicitInstantiation)
@@ -500,15 +498,30 @@ bool Sema::DiagnoseUninstantiableTemplate(SourceLocation PointOfInstantiation,
     // we're lexically inside it.
     Instantiation->setInvalidDecl();
   } else if (InstantiatedFromMember) {
-    Diag(PointOfInstantiation,
-         diag::err_implicit_instantiate_member_undefined)
-      << InstantiationTy;
-    Diag(Pattern->getLocation(), diag::note_member_declared_at);
+    if (isa<FunctionDecl>(Instantiation)) {
+      Diag(PointOfInstantiation,
+           diag::err_explicit_instantiation_undefined_member)
+        << 1 << Instantiation->getDeclName() << Instantiation->getDeclContext();
+    } else {
+      Diag(PointOfInstantiation,
+           diag::err_implicit_instantiate_member_undefined)
+        << InstantiationTy;
+    }
+    Diag(Pattern->getLocation(), isa<FunctionDecl>(Instantiation)
+                                     ? diag::note_explicit_instantiation_here
+                                     : diag::note_member_declared_at);
   } else {
-    Diag(PointOfInstantiation, diag::err_template_instantiate_undefined)
-      << (TSK != TSK_ImplicitInstantiation)
-      << InstantiationTy;
-    Diag(Pattern->getLocation(), diag::note_template_decl_here);
+    if (isa<FunctionDecl>(Instantiation))
+      Diag(PointOfInstantiation,
+           diag::err_explicit_instantiation_undefined_func_template)
+        << Pattern;
+    else
+      Diag(PointOfInstantiation, diag::err_template_instantiate_undefined)
+        << (TSK != TSK_ImplicitInstantiation)
+        << InstantiationTy;
+    Diag(Pattern->getLocation(), isa<FunctionDecl>(Instantiation)
+                                     ? diag::note_explicit_instantiation_here
+                                     : diag::note_template_decl_here);
   }
 
   // In general, Instantiation isn't marked invalid to get more than one
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 3f4a0f6f39a..75d7f70a636 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -3554,23 +3554,38 @@ void Sema::InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
   const FunctionDecl *PatternDecl = Function->getTemplateInstantiationPattern();
   assert(PatternDecl && "instantiating a non-template");
 
-  Stmt *Pattern = PatternDecl->getBody(PatternDecl);
-  assert(PatternDecl && "template definition is not a template");
-  if (!Pattern) {
-    // Try to find a defaulted definition
-    PatternDecl->isDefined(PatternDecl);
-  }
-  assert(PatternDecl && "template definition is not a template");
+  const FunctionDecl *PatternDef = PatternDecl->getDefinition();
+  Stmt *Pattern = PatternDef->getBody(PatternDef);
+  if (PatternDef)
+    PatternDecl = PatternDef;
 
   // FIXME: We need to track the instantiation stack in order to know which
   // definitions should be visible within this instantiation.
   if (DiagnoseUninstantiableTemplate(PointOfInstantiation, Function,
                                 Function->getInstantiatedFromMemberFunction(),
-                                     PatternDecl, PatternDecl, TSK,
-                                     /*Complain*/DefinitionRequired))
-     return;
-
+                                     PatternDecl, PatternDef, TSK,
+                                     /*Complain*/DefinitionRequired)) {
+    if (DefinitionRequired)
+      Function->setInvalidDecl();
+    else if (TSK == TSK_ExplicitInstantiationDefinition) {
+      // Try again at the end of the translation unit (at which point a
+      // definition will be required).
+      assert(!Recursive);
+      PendingInstantiations.push_back(
+        std::make_pair(Function, PointOfInstantiation));
+    } else if (TSK == TSK_ImplicitInstantiation) {
+      if (AtEndOfTU && !getDiagnostics().hasErrorOccurred()) {
+        Diag(PointOfInstantiation, diag::warn_func_template_missing)
+          << Function;
+        Diag(PatternDecl->getLocation(), diag::note_forward_template_decl);
+        if (getLangOpts().CPlusPlus11)
+          Diag(PointOfInstantiation, diag::note_inst_declaration_hint)
+            << Function;
+      }
+    }
 
+    return;
+  }
 
   // Postpone late parsed template instantiations.
   if (PatternDecl->isLateTemplateParsed() &&
@@ -3604,40 +3619,9 @@ void Sema::InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
     Pattern = PatternDecl->getBody(PatternDecl);
   }
 
-  // FIXME: Check if we could sink these diagnostics in
-  // DiagnoseUninstantiableTemplate.
-  if (!Pattern && !PatternDecl->isDefaulted()) {
-    if (DefinitionRequired) {
-      if (Function->getPrimaryTemplate())
-        Diag(PointOfInstantiation,
-             diag::err_explicit_instantiation_undefined_func_template)
-          << Function->getPrimaryTemplate();
-      else
-        Diag(PointOfInstantiation,
-             diag::err_explicit_instantiation_undefined_member)
-          << 1 << Function->getDeclName() << Function->getDeclContext();
-
-      if (PatternDecl)
-        Diag(PatternDecl->getLocation(),
-             diag::note_explicit_instantiation_here);
-      Function->setInvalidDecl();
-    } else if (TSK == TSK_ExplicitInstantiationDefinition) {
-      assert(!Recursive);
-      PendingInstantiations.push_back(
-        std::make_pair(Function, PointOfInstantiation));
-    } else if (TSK == TSK_ImplicitInstantiation) {
-      if (AtEndOfTU && !getDiagnostics().hasErrorOccurred()) {
-        Diag(PointOfInstantiation, diag::warn_func_template_missing)
-          << Function;
-        Diag(PatternDecl->getLocation(), diag::note_forward_template_decl);
-        if (getLangOpts().CPlusPlus11)
-          Diag(PointOfInstantiation, diag::note_inst_declaration_hint)
-            << Function;
-      }
-    }
-
-    return;
-  }
+  // Note, we should never try to instantiate a deleted function template.
+  assert((Pattern || PatternDecl->isDefaulted()) &&
+         "unexpected kind of function template definition");
 
   // C++1y [temp.explicit]p10:
   //   Except for inline functions, declarations with types deduced from their
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index 091a4e34e19..8a49f6120cf 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -6890,6 +6890,10 @@ bool Sema::hasVisibleDefinition(NamedDecl *D, NamedDecl **Suggested,
       return false;
     }
     D = ED->getDefinition();
+  } else if (auto *FD = dyn_cast<FunctionDecl>(D)) {
+    if (auto *Pattern = FD->getTemplateInstantiationPattern())
+      FD = Pattern;
+    D = FD->getDefinition();
   }
   assert(D && "missing definition for pattern of instantiated definition");
 
@@ -6897,7 +6901,7 @@ bool Sema::hasVisibleDefinition(NamedDecl *D, NamedDecl **Suggested,
   if (isVisible(D))
     return true;
 
-  // The external source may have additional definitions of this type that are
+  // The external source may have additional definitions of this entity that are
   // visible, so complete the redeclaration chain now and ask again.
   if (auto *Source = Context.getExternalSource()) {
     Source->CompleteRedeclChain(D);
diff --git a/clang/test/Modules/Inputs/merge-template-pattern-visibility/a.h b/clang/test/Modules/Inputs/merge-template-pattern-visibility/a.h
index 7f9b6497e72..e6592027611 100644
--- a/clang/test/Modules/Inputs/merge-template-pattern-visibility/a.h
+++ b/clang/test/Modules/Inputs/merge-template-pattern-visibility/a.h
@@ -3,3 +3,4 @@ template<typename T> struct B;
 
 template<typename, typename> struct A {};
 template<typename T> struct B : A<T> {};
+template<typename T> inline auto C(T) {}
diff --git a/clang/test/Modules/Inputs/merge-template-pattern-visibility/b.h b/clang/test/Modules/Inputs/merge-template-pattern-visibility/b.h
index 5ed18e7e7c5..6db3c2c6c9f 100644
--- a/clang/test/Modules/Inputs/merge-template-pattern-visibility/b.h
+++ b/clang/test/Modules/Inputs/merge-template-pattern-visibility/b.h
@@ -3,7 +3,9 @@ template<typename T> struct B;
 
 template<typename, typename> struct A {};
 template<typename T> struct B : A<T> {};
+template<typename T> inline auto C(T) {}
 
 inline void f() {
   B<int> bi;
+  C(0);
 }
diff --git a/clang/test/Modules/merge-template-pattern-visibility.cpp b/clang/test/Modules/merge-template-pattern-visibility.cpp
index db759b5a46a..b97f9f113e3 100644
--- a/clang/test/Modules/merge-template-pattern-visibility.cpp
+++ b/clang/test/Modules/merge-template-pattern-visibility.cpp
@@ -1,4 +1,4 @@
 // RUN: rm -rf %t
-// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -fno-modules-error-recovery \
+// RUN: %clang_cc1 -fmodules -fno-modules-error-recovery -std=c++14 \
 // RUN:            -fmodule-name=X -emit-module %S/Inputs/merge-template-pattern-visibility/module.modulemap -x c++ \
-// RUN:            -fmodules-local-submodule-visibility
+// RUN:            -fmodules-local-submodule-visibility -o %t/X.pcm