From c4a1e0efe6b0767dfb5861a7e8814d7db0c0de8a Mon Sep 17 00:00:00 2001
From: Richard Trieu <57020969+Weverything@users.noreply.github.com>
Date: Sun, 1 Dec 2024 19:21:42 -0800
Subject: [PATCH] [clang] Remove redundant integer values in template type
 diffing

Look through SubstNonTypeTemplateParmExpr to find an IntegerLiteral
node when attempting to determine if extra info is printed via
the aka mechanism.  This will avoid printing types such as
"array<5 aka 5>" and will only show "array<5>".
---
 clang/lib/AST/ASTDiagnostic.cpp               | 10 ++++--
 .../test/Misc/diag-template-diffing-cxx98.cpp | 32 +++++++++++++++++++
 2 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/clang/lib/AST/ASTDiagnostic.cpp b/clang/lib/AST/ASTDiagnostic.cpp
index 4f677b60e60d..7b873ee9833b 100644
--- a/clang/lib/AST/ASTDiagnostic.cpp
+++ b/clang/lib/AST/ASTDiagnostic.cpp
@@ -1899,11 +1899,17 @@ class TemplateDiff {
 
     E = E->IgnoreImpCasts();
 
-    if (isa<IntegerLiteral>(E)) return false;
+    auto CheckIntegerLiteral = [](Expr *E) {
+      if (auto *TemplateExpr = dyn_cast<SubstNonTypeTemplateParmExpr>(E))
+        E = TemplateExpr->getReplacement();
+      return isa<IntegerLiteral>(E);
+    };
+
+    if (CheckIntegerLiteral(E)) return false;
 
     if (UnaryOperator *UO = dyn_cast<UnaryOperator>(E))
       if (UO->getOpcode() == UO_Minus)
-        if (isa<IntegerLiteral>(UO->getSubExpr()))
+        if (CheckIntegerLiteral(UO->getSubExpr()))
           return false;
 
     if (isa<CXXBoolLiteralExpr>(E))
diff --git a/clang/test/Misc/diag-template-diffing-cxx98.cpp b/clang/test/Misc/diag-template-diffing-cxx98.cpp
index 7b1a08c6b869..888b9f8b0e5e 100644
--- a/clang/test/Misc/diag-template-diffing-cxx98.cpp
+++ b/clang/test/Misc/diag-template-diffing-cxx98.cpp
@@ -47,3 +47,35 @@ namespace qualifiers {
 
   // CHECK: candidate template ignored: deduced conflicting types for parameter 'T' ('const vector<...>' vs. 'volatile vector<...>')
 }
+
+namespace integers {
+  template <int x>
+  class wrapper{};
+
+  template <int x>
+  class foo {
+   public:
+    wrapper<x> make();
+  };
+
+  wrapper<1> w1 = foo<2>().make();
+  // CHECK: no viable conversion from 'wrapper<2>' to 'wrapper<1>'
+
+  wrapper<1> w2 = foo<-3>().make();
+  // CHECK: no viable conversion from 'wrapper<-3>' to 'wrapper<1>'
+
+  template <int x>
+  wrapper<x> make();
+
+  wrapper<1> w3 = make<4>();
+  // CHECK: no viable conversion from 'wrapper<4>' to 'wrapper<1>'
+
+  template <int x>
+  wrapper<-x> makeNegative();
+
+  wrapper<1> w4 = makeNegative<5>();
+  // CHECK: no viable conversion from 'wrapper<-5>' to 'wrapper<1>'
+
+  wrapper<1> w5 = makeNegative<-6>();
+  // CHECK: no viable conversion from 'wrapper<6>' to 'wrapper<1>'
+}