diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index d2e5bd284d350..2ac5f4aab75dc 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -452,6 +452,7 @@ Bug Fixes to AST Handling
 
 Miscellaneous Bug Fixes
 ^^^^^^^^^^^^^^^^^^^^^^^
+- Fixed missing diagnostics of ``diagnose_if`` on templates involved in initialization. (#GH160776)
 
 Miscellaneous Clang Crashes Fixed
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index 0d0d2c00eb5d4..922fcacdd7ae9 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -7539,7 +7539,7 @@ PerformConstructorInitialization(Sema &S,
 
   // Only check access if all of that succeeded.
   S.CheckConstructorAccess(Loc, Constructor, Step.Function.FoundDecl, Entity);
-  if (S.DiagnoseUseOfDecl(Step.Function.FoundDecl, Loc))
+  if (S.DiagnoseUseOfOverloadedDecl(Constructor, Loc))
     return ExprError();
 
   if (const ArrayType *AT = S.Context.getAsArrayType(Entity.getType()))
@@ -8092,7 +8092,7 @@ ExprResult InitializationSequence::Perform(Sema &S,
 
         S.CheckConstructorAccess(Kind.getLocation(), Constructor, FoundFn,
                                  Entity);
-        if (S.DiagnoseUseOfDecl(FoundFn, Kind.getLocation()))
+        if (S.DiagnoseUseOfOverloadedDecl(Constructor, Kind.getLocation()))
           return ExprError();
 
         CastKind = CK_ConstructorConversion;
@@ -8102,7 +8102,7 @@ ExprResult InitializationSequence::Perform(Sema &S,
         CXXConversionDecl *Conversion = cast<CXXConversionDecl>(Fn);
         S.CheckMemberOperatorAccess(Kind.getLocation(), CurInit.get(), nullptr,
                                     FoundFn);
-        if (S.DiagnoseUseOfDecl(FoundFn, Kind.getLocation()))
+        if (S.DiagnoseUseOfOverloadedDecl(Conversion, Kind.getLocation()))
           return ExprError();
 
         CurInit = S.BuildCXXMemberCallExpr(CurInit.get(), FoundFn, Conversion,
diff --git a/clang/test/Parser/cxx0x-lambda-expressions.cpp b/clang/test/Parser/cxx0x-lambda-expressions.cpp
index f90f8ce27c53e..5b57c7f638e8a 100644
--- a/clang/test/Parser/cxx0x-lambda-expressions.cpp
+++ b/clang/test/Parser/cxx0x-lambda-expressions.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -Wno-unused-value -verify=expected,cxx14ext,cxx17ext,cxx20ext,cxx23ext -std=c++03 -Wno-c99-designator %s -Wno-c++11-extensions
+// RUN: %clang_cc1 -fsyntax-only -Wno-unused-value -verify=expected,cxx14ext,cxx17ext,cxx20ext,cxx23ext -std=c++03 -Wno-c99-designator %s -Wno-c++11-extensions -Wno-local-type-template-args
 // RUN: %clang_cc1 -fsyntax-only -Wno-unused-value -verify=expected,cxx14ext,cxx17ext,cxx20ext,cxx23ext -std=c++11 -Wno-c99-designator %s
 // RUN: %clang_cc1 -fsyntax-only -Wno-unused-value -verify=expected,cxx17ext,cxx20ext,cxx23ext          -std=c++14 -Wno-c99-designator %s
 // RUN: %clang_cc1 -fsyntax-only -Wno-unused-value -verify=expected,cxx20ext,cxx23ext                   -std=c++17 -Wno-c99-designator %s
diff --git a/clang/test/SemaCXX/diagnose_if.cpp b/clang/test/SemaCXX/diagnose_if.cpp
index 1b9e660c4e224..0af8bb76496ea 100644
--- a/clang/test/SemaCXX/diagnose_if.cpp
+++ b/clang/test/SemaCXX/diagnose_if.cpp
@@ -1,5 +1,7 @@
 // RUN: %clang_cc1 %s -verify -fno-builtin -std=c++14
+// RUN: %clang_cc1 %s -verify -fno-builtin -std=c++20 -verify=expected,cxx20
 // RUN: %clang_cc1 %s -verify -fno-builtin -std=c++14 -fexperimental-new-constant-interpreter
+// RUN: %clang_cc1 %s -verify -fno-builtin -std=c++20 -verify=expected,cxx20 -fexperimental-new-constant-interpreter
 
 #define _diagnose_if(...) __attribute__((diagnose_if(__VA_ARGS__)))
 
@@ -665,3 +667,28 @@ void run() {
   switch (constexpr Foo i = 2) { default: break; } // expected-error{{oh no}}
 }
 }
+
+namespace GH160776 {
+
+struct ConstructorTemplate {
+  template <class T>
+  explicit ConstructorTemplate(T x)
+      _diagnose_if(sizeof(T) == sizeof(char), "oh no", "error") {} // expected-note {{diagnose_if}}
+
+  template <class T>
+#if __cplusplus >= 202002L
+  requires (sizeof(T) == 1) // cxx20-note {{evaluated to false}}
+#endif
+  operator T() _diagnose_if(sizeof(T) == sizeof(char), "oh no", "error") { // expected-note {{diagnose_if}} \
+                                                                           // cxx20-note {{constraints not satisfied}}
+    return T{};
+  }
+};
+
+void run() {
+  ConstructorTemplate x('1'); // expected-error {{oh no}}
+  char y = x; // expected-error {{oh no}}
+  int z = x; // cxx20-error {{no viable conversion}}
+}
+
+}
diff --git a/clang/test/SemaCXX/lambda-expressions.cpp b/clang/test/SemaCXX/lambda-expressions.cpp
index 8ea8e324cf5d2..f9d7cfcbbd18d 100644
--- a/clang/test/SemaCXX/lambda-expressions.cpp
+++ b/clang/test/SemaCXX/lambda-expressions.cpp
@@ -149,7 +149,8 @@ namespace PR12031 {
   void f(int i, X x);
   void g() {
     const int v = 10;
-    f(v, [](){});
+    f(v, [](){}); // cxx03-warning {{template argument uses local type}} \
+                         // cxx03-note {{while substituting}}
   }
 }
 
@@ -572,26 +573,37 @@ namespace PR27994 {
 struct A { template <class T> A(T); };
 
 template <class T>
-struct B {
+struct B { // #PR27994_B
   int x;
-  A a = [&] { int y = x; };
-  A b = [&] { [&] { [&] { int y = x; }; }; };
-  A d = [&](auto param) { int y = x; }; // cxx03-cxx11-error {{'auto' not allowed in lambda parameter}}
-  A e = [&](auto param) { [&] { [&](auto param2) { int y = x; }; }; }; // cxx03-cxx11-error 2 {{'auto' not allowed in lambda parameter}}
+  A a = [&] { int y = x; }; // cxx03-warning {{template argument uses unnamed type}} \
+                            //   cxx03-note {{while substituting}} cxx03-note {{unnamed type used}}
+  A b = [&] { [&] { [&] { int y = x; }; }; }; // cxx03-warning {{template argument uses unnamed type}} \
+                                              //   cxx03-note {{while substituting}} cxx03-note {{unnamed type used}}
+  A d = [&](auto param) { int y = x; }; // cxx03-cxx11-error {{'auto' not allowed in lambda parameter}} \
+                                        // cxx03-warning {{template argument uses unnamed type}} \
+                                        //  cxx03-note {{while substituting}} cxx03-note {{unnamed type used}}
+  A e = [&](auto param) { [&] { [&](auto param2) { int y = x; }; }; }; // cxx03-cxx11-error 2 {{'auto' not allowed in lambda parameter}} \
+                                                                       // cxx03-warning {{template argument uses unnamed type}} \
+                                                                       //  cxx03-note {{while substituting}} cxx03-note {{unnamed type used}}
 };
 
 B<int> b;
+// cxx03-note@#PR27994_B 4{{in instantiation of default member initializer}}
+// cxx03-note@-2 4{{in evaluation of exception}}
 
 template <class T> struct C {
   struct D {
+    // cxx03-note@-1 {{in instantiation of default member initializer}}
     int x;
-    A f = [&] { int y = x; };
+    A f = [&] { int y = x; }; // cxx03-warning {{template argument uses unnamed type}} \
+                              // cxx03-note {{while substituting}} cxx03-note {{unnamed type used}}
   };
 };
 
 int func() {
   C<int> a;
   decltype(a)::D b;
+  // cxx03-note@-1 {{in evaluation of exception}}
 }
 }
 
@@ -606,8 +618,12 @@ struct S1 {
 
 void foo1() {
   auto s0 = S1([name=]() {}); // expected-error {{expected expression}}
+                                     // cxx03-warning@-1 {{template argument uses local type}} \
+                                     // cxx03-note@-1 {{while substituting deduced template arguments}}
   auto s1 = S1([name=name]() {}); // expected-error {{use of undeclared identifier 'name'; did you mean 'name1'?}}
                                   // cxx03-cxx11-warning@-1 {{initialized lambda captures are a C++14 extension}}
+                                  // cxx03-warning@-2 {{template argument uses local type}} \
+                                  // cxx03-note@-2 {{while substituting deduced template arguments}}
 }
 }