Introduce support for emitting diagnostics (warnings + their notes)

that are suppressed during template argument deduction. This change
queues diagnostics computed during template argument deduction. Then,
if the resulting function template specialization or partial
specialization is chosen by overload resolution or partial ordering
(respectively), we will emit the queued diagnostics at that point. 

This addresses most of PR6784. However, the check for unnamed/local
template arguments (which existed before this change) is still only
skin-deep, and needs to be extended to look deeper into types. It must
be improved to finish PR6784.

llvm-svn: 116373

1 files changed, 18 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 68bb2b07233..609465c5052 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -56,6 +56,24 @@ using namespace sema;
 /// referenced), false otherwise.
 ///
 bool Sema::DiagnoseUseOfDecl(NamedDecl *D, SourceLocation Loc) {
+  if (getLangOptions().CPlusPlus && isa<FunctionDecl>(D)) {
+    // If there were any diagnostics suppressed by template argument deduction,
+    // emit them now.
+    llvm::DenseMap<Decl *, llvm::SmallVector<PartialDiagnosticAt, 1> >::iterator
+      Pos = SuppressedDiagnostics.find(D->getCanonicalDecl());
+    if (Pos != SuppressedDiagnostics.end()) {
+      llvm::SmallVectorImpl<PartialDiagnosticAt> &Suppressed = Pos->second;
+      for (unsigned I = 0, N = Suppressed.size(); I != N; ++I)
+        Diag(Suppressed[I].first, Suppressed[I].second);
+      
+      // Clear out the list of suppressed diagnostics, so that we don't emit
+      // them again for this specialization. However, we don't remove this
+      // entry from the table, because we want to avoid ever emitting these
+      // diagnostics again.
+      Suppressed.clear();
+    }
+  }
+
   // See if the decl is deprecated.
   if (const DeprecatedAttr *DA = D->getAttr<DeprecatedAttr>())
     EmitDeprecationWarning(D, DA->getMessage(), Loc);