From 555c9673fd8c2380bf47f41450ce932472496376 Mon Sep 17 00:00:00 2001
From: Richard Trieu <rtrieu@google.com>
Date: Thu, 26 Feb 2015 02:40:48 +0000
Subject: [PATCH] Update assumption in template diffing about integer template
 arguments.

Fix for PR22017.  Integer template arguments are automatically bit extended to
the size of the integer type.  In template diffing, evaluated expressions were
not having their results extending, leading to comparing two APSInt's with
different widths.  Apply the proper bit extending when evaluating template
arguments.  This mainly affected bool template arguments.

llvm-svn: 230603
---
 clang/lib/AST/ASTDiagnostic.cpp           | 20 ++++++++++++++------
 clang/test/Misc/diag-template-diffing.cpp | 13 +++++++++++++
 2 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/clang/lib/AST/ASTDiagnostic.cpp b/clang/lib/AST/ASTDiagnostic.cpp
index f55e032..000588f 100644
--- a/clang/lib/AST/ASTDiagnostic.cpp
+++ b/clang/lib/AST/ASTDiagnostic.cpp
@@ -1003,9 +1003,11 @@ class TemplateDiff {
       Tree.SetDefault(FromIter.isEnd() && FromExpr, ToIter.isEnd() && ToExpr);
       if (FromDefaultNonTypeDecl->getType()->isIntegralOrEnumerationType()) {
         if (FromExpr)
-          HasFromInt = GetInt(Context, FromIter, FromExpr, FromInt);
+          HasFromInt = GetInt(Context, FromIter, FromExpr, FromInt,
+                              FromDefaultNonTypeDecl->getType());
         if (ToExpr)
-          HasToInt = GetInt(Context, ToIter, ToExpr, ToInt);
+          HasToInt = GetInt(Context, ToIter, ToExpr, ToInt,
+                            ToDefaultNonTypeDecl->getType());
       }
       if (HasFromInt && HasToInt) {
         Tree.SetNode(FromInt, ToInt, HasFromInt, HasToInt);
@@ -1026,9 +1028,11 @@ class TemplateDiff {
 
     if (HasFromInt || HasToInt) {
       if (!HasFromInt && FromExpr)
-        HasFromInt = GetInt(Context, FromIter, FromExpr, FromInt);
+        HasFromInt = GetInt(Context, FromIter, FromExpr, FromInt,
+                            FromDefaultNonTypeDecl->getType());
       if (!HasToInt && ToExpr)
-        HasToInt = GetInt(Context, ToIter, ToExpr, ToInt);
+        HasToInt = GetInt(Context, ToIter, ToExpr, ToInt,
+                          ToDefaultNonTypeDecl->getType());
       Tree.SetNode(FromInt, ToInt, HasFromInt, HasToInt);
       if (HasFromInt && HasToInt) {
         Tree.SetSame(FromInt == ToInt);
@@ -1210,9 +1214,11 @@ class TemplateDiff {
   }
 
   /// GetInt - Retrieves the template integer argument, including evaluating
-  /// default arguments.
+  /// default arguments.  If the value comes from an expression, extend the
+  /// APSInt to size of IntegerType to match the behavior in
+  /// Sema::CheckTemplateArgument
   static bool GetInt(ASTContext &Context, const TSTiterator &Iter,
-                     Expr *ArgExpr, llvm::APSInt &Int) {
+                     Expr *ArgExpr, llvm::APSInt &Int, QualType IntegerType) {
     // Default, value-depenedent expressions require fetching
     // from the desugared TemplateArgument, otherwise expression needs to
     // be evaluatable.
@@ -1224,12 +1230,14 @@ class TemplateDiff {
         case TemplateArgument::Expression:
           ArgExpr = Iter.getDesugar().getAsExpr();
           Int = ArgExpr->EvaluateKnownConstInt(Context);
+          Int = Int.extOrTrunc(Context.getTypeSize(IntegerType));
           return true;
         default:
           llvm_unreachable("Unexpected template argument kind");
       }
     } else if (ArgExpr->isEvaluatable(Context)) {
       Int = ArgExpr->EvaluateKnownConstInt(Context);
+      Int = Int.extOrTrunc(Context.getTypeSize(IntegerType));
       return true;
     }
 
diff --git a/clang/test/Misc/diag-template-diffing.cpp b/clang/test/Misc/diag-template-diffing.cpp
index 9f4806f..0f2edfb 100644
--- a/clang/test/Misc/diag-template-diffing.cpp
+++ b/clang/test/Misc/diag-template-diffing.cpp
@@ -1261,6 +1261,19 @@ void foo(const T &t) {
 // CHECK-ELIDE-NOTREE: binding of reference to type 'condition<[...]>' to a value of type 'const condition<[...]>' drops qualifiers
 }
 
+namespace BoolArgumentBitExtended {
+template <bool B> struct BoolT {};
+
+template <typename T> void foo(T) {}
+
+void test() {
+  BoolT<false> X;
+  foo<BoolT<true>>(X);
+}
+// CHECK-ELIDE-NOTREE: no matching function for call to 'foo'
+// CHECK-ELIDE-NOTREE: candidate function [with T = BoolArgumentBitExtended::BoolT<true>] not viable: no known conversion from 'BoolT<0>' to 'BoolT<1>' for 1st argument
+}
+
 // CHECK-ELIDE-NOTREE: {{[0-9]*}} errors generated.
 // CHECK-NOELIDE-NOTREE: {{[0-9]*}} errors generated.
 // CHECK-ELIDE-TREE: {{[0-9]*}} errors generated.
-- 
2.7.4