Index: clang/lib/Sema/SemaInit.cpp
===================================================================
--- clang/lib/Sema/SemaInit.cpp
+++ clang/lib/Sema/SemaInit.cpp
@@ -8360,40 +8360,49 @@
     // No narrowing occurred.
     return;
 
-  case NK_Type_Narrowing:
+  case NK_Type_Narrowing: {
     // This was a floating-to-integer conversion, which is always considered a
     // narrowing conversion even if the value is a constant and can be
     // represented exactly as an integer.
-    S.Diag(PostInit->getLocStart(),
-           (S.getLangOpts().MicrosoftExt || !S.getLangOpts().CPlusPlus11)
-               ? diag::warn_init_list_type_narrowing
-               : diag::ext_init_list_type_narrowing)
-      << PostInit->getSourceRange()
-      << PreNarrowingType.getLocalUnqualifiedType()
-      << EntityType.getLocalUnqualifiedType();
-    break;
-
-  case NK_Constant_Narrowing:
+    bool DiagErr =
+        S.getLangOpts().CPlusPlus11 &&
+        (!S.getLangOpts().MicrosoftExt ||
+         S.getLangOpts().isCompatibleWithMSVC(LangOptions::MSVC2015));
+    S.Diag(PostInit->getLocStart(), !DiagErr
+                                        ? diag::warn_init_list_type_narrowing
+                                        : diag::ext_init_list_type_narrowing)
+        << PostInit->getSourceRange()
+        << PreNarrowingType.getLocalUnqualifiedType()
+        << EntityType.getLocalUnqualifiedType();
+  } break;
+
+  case NK_Constant_Narrowing: {
     // A constant value was narrowed.
+    bool DiagErr =
+        S.getLangOpts().CPlusPlus11 &&
+        (!S.getLangOpts().MicrosoftExt ||
+         S.getLangOpts().isCompatibleWithMSVC(LangOptions::MSVC2015));
     S.Diag(PostInit->getLocStart(),
-           (S.getLangOpts().MicrosoftExt || !S.getLangOpts().CPlusPlus11)
-               ? diag::warn_init_list_constant_narrowing
-               : diag::ext_init_list_constant_narrowing)
-      << PostInit->getSourceRange()
-      << ConstantValue.getAsString(S.getASTContext(), ConstantType)
-      << EntityType.getLocalUnqualifiedType();
-    break;
-
-  case NK_Variable_Narrowing:
+           !DiagErr ? diag::warn_init_list_constant_narrowing
+                    : diag::ext_init_list_constant_narrowing)
+        << PostInit->getSourceRange()
+        << ConstantValue.getAsString(S.getASTContext(), ConstantType)
+        << EntityType.getLocalUnqualifiedType();
+  } break;
+
+  case NK_Variable_Narrowing: {
     // A variable's value may have been narrowed.
+    bool DiagErr =
+        S.getLangOpts().CPlusPlus11 &&
+        (!S.getLangOpts().MicrosoftExt ||
+         S.getLangOpts().isCompatibleWithMSVC(LangOptions::MSVC2015));
     S.Diag(PostInit->getLocStart(),
-           (S.getLangOpts().MicrosoftExt || !S.getLangOpts().CPlusPlus11)
-               ? diag::warn_init_list_variable_narrowing
-               : diag::ext_init_list_variable_narrowing)
-      << PostInit->getSourceRange()
-      << PreNarrowingType.getLocalUnqualifiedType()
-      << EntityType.getLocalUnqualifiedType();
-    break;
+           !DiagErr ? diag::warn_init_list_variable_narrowing
+                    : diag::ext_init_list_variable_narrowing)
+        << PostInit->getSourceRange()
+        << PreNarrowingType.getLocalUnqualifiedType()
+        << EntityType.getLocalUnqualifiedType();
+  } break;
   }
 
   SmallString<128> StaticCast;
Index: clang/test/SemaCXX/ms-initlist-narrowing.cpp
===================================================================
--- /dev/null
+++ clang/test/SemaCXX/ms-initlist-narrowing.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 %s -fsyntax-only -verify -fms-extensions -fms-compatibility-version=19.0 -std=c++11
+
+int ai[] = { 1, 2.0 };  // expected-error {{type 'double' cannot be narrowed to 'int' in initializer list}} expected-note {{silence}}
+
+template<typename T>
+struct Agg {
+  T t;
+};
+
+void f(int i) {
+  // Constant expression.
+  Agg<float> f8 = {1E50};  // expected-error {{constant expression evaluates to 1.000000e+50 which cannot be narrowed to type 'float'}} expected-note {{silence}}
+
+  // Non-constant expression.
+  double d = 1.0;
+  Agg<float> f2 = {d};  // expected-error {{non-constant-expression cannot be narrowed from type 'double' to 'float'}} expected-note {{silence}}
+}