[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>".

Author: Weverything

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))

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>'
+}