diff --git a/clang-tools-extra/clangd/unittests/HoverTests.cpp b/clang-tools-extra/clangd/unittests/HoverTests.cpp
--- a/clang-tools-extra/clangd/unittests/HoverTests.cpp
+++ b/clang-tools-extra/clangd/unittests/HoverTests.cpp
@@ -969,6 +969,52 @@
          HI.Definition = "template <typename T> using AA = A<T>";
          HI.Type = {"A<T>", "type-parameter-0-0"}; // FIXME: should be 'T'
          HI.TemplateParameters = {{{"typename"}, std::string("T"), llvm::None}};
+       }},
+      {// Constant array
+       R"cpp(
+          using m_int = int;
+
+          m_int ^[[arr]][10];
+         )cpp",
+       [](HoverInfo &HI) {
+         HI.Name = "arr";
+         HI.NamespaceScope = "";
+         HI.LocalScope = "";
+         HI.Kind = index::SymbolKind::Variable;
+         HI.Definition = "m_int arr[10]";
+         HI.Type = {"m_int[10]", "int[10]"};
+       }},
+      {// Incomplete array
+       R"cpp(
+          using m_int = int;
+
+          extern m_int ^[[arr]][];
+         )cpp",
+       [](HoverInfo &HI) {
+         HI.Name = "arr";
+         HI.NamespaceScope = "";
+         HI.LocalScope = "";
+         HI.Kind = index::SymbolKind::Variable;
+         HI.Definition = "extern m_int arr[]";
+         HI.Type = {"m_int[]", "int[]"};
+       }},
+      {// Dependent size array
+       R"cpp(
+          using m_int = int;
+
+          template<int Size>
+          struct Test {
+            m_int ^[[arr]][Size];
+          };
+         )cpp",
+       [](HoverInfo &HI) {
+         HI.Name = "arr";
+         HI.NamespaceScope = "";
+         HI.LocalScope = "Test<Size>::";
+         HI.AccessSpecifier = "public";
+         HI.Kind = index::SymbolKind::Field;
+         HI.Definition = "m_int arr[Size]";
+         HI.Type = {"m_int[Size]", "int[Size]"};
        }}};
   for (const auto &Case : Cases) {
     SCOPED_TRACE(Case.Code);
diff --git a/clang/lib/AST/ASTDiagnostic.cpp b/clang/lib/AST/ASTDiagnostic.cpp
--- a/clang/lib/AST/ASTDiagnostic.cpp
+++ b/clang/lib/AST/ASTDiagnostic.cpp
@@ -131,6 +131,38 @@
       }
     }
 
+    if (const auto *CAT = dyn_cast<ConstantArrayType>(Ty)) {
+      QualType ElementTy =
+          desugarForDiagnostic(Context, CAT->getElementType(), ShouldAKA);
+      QT = Context.getConstantArrayType(
+          ElementTy, CAT->getSize(), CAT->getSizeExpr(), CAT->getSizeModifier(),
+          CAT->getIndexTypeCVRQualifiers());
+      break;
+    }
+    if (const auto *VAT = dyn_cast<VariableArrayType>(Ty)) {
+      QualType ElementTy =
+          desugarForDiagnostic(Context, VAT->getElementType(), ShouldAKA);
+      QT = Context.getVariableArrayType(
+          ElementTy, VAT->getSizeExpr(), VAT->getSizeModifier(),
+          VAT->getIndexTypeCVRQualifiers(), VAT->getBracketsRange());
+      break;
+    }
+    if (const auto *DSAT = dyn_cast<DependentSizedArrayType>(Ty)) {
+      QualType ElementTy =
+          desugarForDiagnostic(Context, DSAT->getElementType(), ShouldAKA);
+      QT = Context.getDependentSizedArrayType(
+          ElementTy, DSAT->getSizeExpr(), DSAT->getSizeModifier(),
+          DSAT->getIndexTypeCVRQualifiers(), DSAT->getBracketsRange());
+      break;
+    }
+    if (const auto *IAT = dyn_cast<IncompleteArrayType>(Ty)) {
+      QualType ElementTy =
+          desugarForDiagnostic(Context, IAT->getElementType(), ShouldAKA);
+      QT = Context.getIncompleteArrayType(ElementTy, IAT->getSizeModifier(),
+                                          IAT->getIndexTypeCVRQualifiers());
+      break;
+    }
+
     // Don't desugar magic Objective-C types.
     if (QualType(Ty,0) == Context.getObjCIdType() ||
         QualType(Ty,0) == Context.getObjCClassType() ||
diff --git a/clang/test/Misc/diag-aka-types.cpp b/clang/test/Misc/diag-aka-types.cpp
--- a/clang/test/Misc/diag-aka-types.cpp
+++ b/clang/test/Misc/diag-aka-types.cpp
@@ -62,3 +62,9 @@
 void (&f3)(decltype(1 + 2)) = 0; // expected-error{{non-const lvalue reference to type 'void (decltype(1 + 2))' (aka 'void (int)') cannot bind to a temporary of type 'int'}}
 decltype(1+2) (&f4)(double, decltype(1 + 2)) = 0; // expected-error{{non-const lvalue reference to type 'decltype(1 + 2) (double, decltype(1 + 2))' (aka 'int (double, int)') cannot bind to a temporary of type 'int'}}
 auto (&f5)() -> decltype(1+2) = 0; // expected-error{{non-const lvalue reference to type 'auto () -> decltype(1 + 2)' (aka 'auto () -> int') cannot bind to a temporary of type 'int'}}
+
+using C = decltype(1+2);;
+C a6[10];
+extern C a8[];
+int a9 = a6; // expected-error{{cannot initialize a variable of type 'int' with an lvalue of type 'C[10]' (aka 'int[10]')}}
+int a10 = a8; // expected-error{{cannot initialize a variable of type 'int' with an lvalue of type 'C[]' (aka 'int[]')}}