When performing template argument deduction, ensure that multiple

deductions of the same template parameter are equivalent. This allows
us to implement the is_same type trait (!).

Also, move template argument deduction into its own file and update a
few build systems with this change (grrrr).



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@72819 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 121 insertions, 0 deletions

diff --git a/lib/Sema/SemaTemplateDeduction.cpp b/lib/Sema/SemaTemplateDeduction.cpp
new file mode 100644
index 0000000000..a55dadd932
--- /dev/null
+++ b/lib/Sema/SemaTemplateDeduction.cpp
@@ -0,0 +1,121 @@
+//===------- SemaTemplateDeduction.cpp - Template Argument Deduction ------===/
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//===----------------------------------------------------------------------===/
+//
+//  This file implements C++ template argument deduction.
+//
+//===----------------------------------------------------------------------===/
+
+#include "Sema.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/DeclTemplate.h"
+#include "clang/AST/StmtVisitor.h"
+#include "clang/AST/Expr.h"
+#include "clang/AST/ExprCXX.h"
+#include "clang/Parse/DeclSpec.h"
+#include "llvm/Support/Compiler.h"
+using namespace clang;
+
+static bool DeduceTemplateArguments(ASTContext &Context, QualType Param, 
+                                    QualType Arg,
+                             llvm::SmallVectorImpl<TemplateArgument> &Deduced) {
+  // We only want to look at the canonical types, since typedefs and
+  // sugar are not part of template argument deduction.
+  Param = Context.getCanonicalType(Param);
+  Arg = Context.getCanonicalType(Arg);
+
+  // If the parameter type is not dependent, just compare the types
+  // directly.
+  if (!Param->isDependentType())
+    return Param == Arg;
+
+  // FIXME: Use a visitor or switch to handle all of the kinds of
+  // types that the parameter may be.
+  if (const TemplateTypeParmType *TemplateTypeParm 
+        = Param->getAsTemplateTypeParmType()) {
+    // The argument type can not be less qualified than the parameter
+    // type.
+    if (Param.isMoreQualifiedThan(Arg))
+      return false;
+
+    assert(TemplateTypeParm->getDepth() == 0 && "Can't deduce with depth > 0");
+	  
+    unsigned Quals = Arg.getCVRQualifiers() & ~Param.getCVRQualifiers();
+    QualType DeducedType = Arg.getQualifiedType(Quals);
+	  unsigned Index = TemplateTypeParm->getIndex();
+
+    if (Deduced[Index].isNull())
+      Deduced[Index] = TemplateArgument(SourceLocation(), DeducedType);
+    else {
+      // C++ [temp.deduct.type]p2: 
+      //   [...] If type deduction cannot be done for any P/A pair, or if for
+      //   any pair the deduction leads to more than one possible set of 
+      //   deduced values, or if different pairs yield different deduced 
+      //   values, or if any template argument remains neither deduced nor 
+      //   explicitly specified, template argument deduction fails.
+      if (Deduced[Index].getAsType() != DeducedType)
+        return false;
+    }
+    return true;
+  }
+
+  if (Param.getCVRQualifiers() != Arg.getCVRQualifiers())
+    return false;
+
+  if (const PointerType *PointerParam = Param->getAsPointerType()) {
+    const PointerType *PointerArg = Arg->getAsPointerType();
+    if (!PointerArg)
+      return false;
+
+    return DeduceTemplateArguments(Context,
+                                   PointerParam->getPointeeType(),
+                                   PointerArg->getPointeeType(),
+                                   Deduced);
+  }
+
+  // FIXME: Many more cases to go (to go).
+  return false;
+}
+
+static bool
+DeduceTemplateArguments(ASTContext &Context, const TemplateArgument &Param,
+                        const TemplateArgument &Arg,
+                        llvm::SmallVectorImpl<TemplateArgument> &Deduced) {
+  assert(Param.getKind() == Arg.getKind() &&
+         "Template argument kind mismatch during deduction");
+  switch (Param.getKind()) {
+  case TemplateArgument::Type: 
+    return DeduceTemplateArguments(Context, Param.getAsType(), 
+                                   Arg.getAsType(), Deduced);
+
+  default:
+    return false;
+  }
+}
+
+static bool 
+DeduceTemplateArguments(ASTContext &Context,
+                        const TemplateArgumentList &ParamList,
+                        const TemplateArgumentList &ArgList,
+                        llvm::SmallVectorImpl<TemplateArgument> &Deduced) {
+  assert(ParamList.size() == ArgList.size());
+  for (unsigned I = 0, N = ParamList.size(); I != N; ++I) {
+    if (!DeduceTemplateArguments(Context, ParamList[I], ArgList[I], Deduced))
+      return false;
+  }
+  return true;
+}
+
+
+bool 
+Sema::DeduceTemplateArguments(ClassTemplatePartialSpecializationDecl *Partial,
+                              const TemplateArgumentList &TemplateArgs) {
+  llvm::SmallVector<TemplateArgument, 4> Deduced;
+  Deduced.resize(Partial->getTemplateParameters()->size());
+  return ::DeduceTemplateArguments(Context, Partial->getTemplateArgs(), 
+                                  TemplateArgs, Deduced);
+}