diff --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
--- a/clang/lib/AST/ASTImporter.cpp
+++ b/clang/lib/AST/ASTImporter.cpp
@@ -5158,8 +5158,6 @@
   // context. This context will be fixed when the actual template declaration
   // is created.
 
-  // FIXME: Import default argument  and constraint expression.
-
   ExpectedSLoc BeginLocOrErr = import(D->getBeginLoc());
   if (!BeginLocOrErr)
     return BeginLocOrErr.takeError();
@@ -5206,6 +5204,14 @@
         ToIDC);
   }
 
+  if (D->hasDefaultArgument()) {
+    Expected<TypeSourceInfo *> ToDefaultArgOrErr =
+        import(D->getDefaultArgumentInfo());
+    if (!ToDefaultArgOrErr)
+      return ToDefaultArgOrErr.takeError();
+    ToD->setDefaultArgument(*ToDefaultArgOrErr);
+  }
+
   return ToD;
 }
 
diff --git a/clang/unittests/AST/ASTImporterTest.cpp b/clang/unittests/AST/ASTImporterTest.cpp
--- a/clang/unittests/AST/ASTImporterTest.cpp
+++ b/clang/unittests/AST/ASTImporterTest.cpp
@@ -880,6 +880,25 @@
                  has(fieldDecl(hasType(dependentSizedArrayType())))))));
 }
 
+TEST_P(ASTImporterOptionSpecificTestBase, TemplateTypeParmDeclNoDefaultArg) {
+  Decl *FromTU = getTuDecl("template<typename T> struct X {};", Lang_CXX03);
+  auto From = FirstDeclMatcher<TemplateTypeParmDecl>().match(
+      FromTU, templateTypeParmDecl(hasName("T")));
+  TemplateTypeParmDecl *To = Import(From, Lang_CXX03);
+  ASSERT_FALSE(To->hasDefaultArgument());
+}
+
+TEST_P(ASTImporterOptionSpecificTestBase, TemplateTypeParmDeclDefaultArg) {
+  Decl *FromTU =
+      getTuDecl("template<typename T = int> struct X {};", Lang_CXX03);
+  auto From = FirstDeclMatcher<TemplateTypeParmDecl>().match(
+      FromTU, templateTypeParmDecl(hasName("T")));
+  TemplateTypeParmDecl *To = Import(From, Lang_CXX03);
+  ASSERT_TRUE(To->hasDefaultArgument());
+  QualType ToArg = To->getDefaultArgument();
+  ASSERT_EQ(ToArg, QualType(To->getASTContext().IntTy));
+}
+
 TEST_P(ASTImporterOptionSpecificTestBase, ImportBeginLocOfDeclRefExpr) {
   Decl *FromTU =
       getTuDecl("class A { public: static int X; }; void f() { (void)A::X; }",
diff --git a/lldb/test/API/commands/expression/import-std-module/deque-basic/TestDequeFromStdModule.py b/lldb/test/API/commands/expression/import-std-module/deque-basic/TestDequeFromStdModule.py
--- a/lldb/test/API/commands/expression/import-std-module/deque-basic/TestDequeFromStdModule.py
+++ b/lldb/test/API/commands/expression/import-std-module/deque-basic/TestDequeFromStdModule.py
@@ -22,7 +22,7 @@
 
         self.runCmd("settings set target.import-std-module true")
 
-        deque_type = "std::deque<int, std::allocator<int> >"
+        deque_type = "std::deque<int>"
         size_type = deque_type + "::size_type"
         value_type = "std::__deque_base<int, std::allocator<int> >::value_type"
         iterator = deque_type + "::iterator"
diff --git a/lldb/test/API/commands/expression/import-std-module/deque-dbg-info-content/TestDbgInfoContentDequeFromStdModule.py b/lldb/test/API/commands/expression/import-std-module/deque-dbg-info-content/TestDbgInfoContentDequeFromStdModule.py
--- a/lldb/test/API/commands/expression/import-std-module/deque-dbg-info-content/TestDbgInfoContentDequeFromStdModule.py
+++ b/lldb/test/API/commands/expression/import-std-module/deque-dbg-info-content/TestDbgInfoContentDequeFromStdModule.py
@@ -22,7 +22,7 @@
 
         self.runCmd("settings set target.import-std-module true")
 
-        deque_type = "std::deque<Foo, std::allocator<Foo> >"
+        deque_type = "std::deque<Foo>"
         size_type = deque_type + "::size_type"
         value_type = "std::__deque_base<Foo, std::allocator<Foo> >::value_type"
 
diff --git a/lldb/test/API/commands/expression/import-std-module/forward_list-dbg-info-content/TestDbgInfoContentForwardListFromStdModule.py b/lldb/test/API/commands/expression/import-std-module/forward_list-dbg-info-content/TestDbgInfoContentForwardListFromStdModule.py
--- a/lldb/test/API/commands/expression/import-std-module/forward_list-dbg-info-content/TestDbgInfoContentForwardListFromStdModule.py
+++ b/lldb/test/API/commands/expression/import-std-module/forward_list-dbg-info-content/TestDbgInfoContentForwardListFromStdModule.py
@@ -22,7 +22,7 @@
 
         self.runCmd("settings set target.import-std-module true")
 
-        list_type = "std::forward_list<Foo, std::allocator<Foo> >"
+        list_type = "std::forward_list<Foo>"
         value_type = list_type + "::value_type"
 
         # FIXME: This has three elements in it but the formatter seems to
diff --git a/lldb/test/API/commands/expression/import-std-module/forward_list/TestForwardListFromStdModule.py b/lldb/test/API/commands/expression/import-std-module/forward_list/TestForwardListFromStdModule.py
--- a/lldb/test/API/commands/expression/import-std-module/forward_list/TestForwardListFromStdModule.py
+++ b/lldb/test/API/commands/expression/import-std-module/forward_list/TestForwardListFromStdModule.py
@@ -22,7 +22,7 @@
 
         self.runCmd("settings set target.import-std-module true")
 
-        list_type = "std::forward_list<int, std::allocator<int> >"
+        list_type = "std::forward_list<int>"
         value_type = list_type + "::value_type"
 
         # FIXME: This has three elements in it but the formatter seems to
diff --git a/lldb/test/API/commands/expression/import-std-module/list-dbg-info-content/TestDbgInfoContentListFromStdModule.py b/lldb/test/API/commands/expression/import-std-module/list-dbg-info-content/TestDbgInfoContentListFromStdModule.py
--- a/lldb/test/API/commands/expression/import-std-module/list-dbg-info-content/TestDbgInfoContentListFromStdModule.py
+++ b/lldb/test/API/commands/expression/import-std-module/list-dbg-info-content/TestDbgInfoContentListFromStdModule.py
@@ -23,7 +23,7 @@
 
         self.runCmd("settings set target.import-std-module true")
 
-        list_type = "std::list<Foo, std::allocator<Foo> >"
+        list_type = "std::list<Foo>"
         size_type = list_type + "::size_type"
         value_type = list_type + "::value_type"
 
diff --git a/lldb/test/API/commands/expression/import-std-module/list/TestListFromStdModule.py b/lldb/test/API/commands/expression/import-std-module/list/TestListFromStdModule.py
--- a/lldb/test/API/commands/expression/import-std-module/list/TestListFromStdModule.py
+++ b/lldb/test/API/commands/expression/import-std-module/list/TestListFromStdModule.py
@@ -22,7 +22,7 @@
 
         self.runCmd("settings set target.import-std-module true")
 
-        list_type = "std::list<int, std::allocator<int> >"
+        list_type = "std::list<int>"
         size_type = list_type + "::size_type"
         value_type = list_type + "::value_type"
 
diff --git a/lldb/test/API/commands/expression/import-std-module/queue/TestQueueFromStdModule.py b/lldb/test/API/commands/expression/import-std-module/queue/TestQueueFromStdModule.py
--- a/lldb/test/API/commands/expression/import-std-module/queue/TestQueueFromStdModule.py
+++ b/lldb/test/API/commands/expression/import-std-module/queue/TestQueueFromStdModule.py
@@ -22,7 +22,7 @@
 
         self.runCmd("settings set target.import-std-module true")
 
-        queue_type = "std::queue<C, std::deque<C, std::allocator<C> > >"
+        queue_type = "std::queue<C>"
         size_type = queue_type + "::size_type"
         value_type = "std::__deque_base<C, std::allocator<C> >::value_type"
 
@@ -54,9 +54,9 @@
                          result_value="5")
 
         # Test std::queue functionality with a std::list.
-        queue_type = "std::queue<C, std::list<C, std::allocator<C> > >"
+        queue_type = "std::queue<C, std::list<C> >"
         size_type = queue_type + "::size_type"
-        value_type = "std::list<C, std::allocator<C> >::value_type"
+        value_type = "std::list<C>::value_type"
         self.expect_expr(
             "q_list",
             result_type=queue_type,
diff --git a/lldb/test/API/commands/expression/import-std-module/stack/TestStackFromStdModule.py b/lldb/test/API/commands/expression/import-std-module/stack/TestStackFromStdModule.py
--- a/lldb/test/API/commands/expression/import-std-module/stack/TestStackFromStdModule.py
+++ b/lldb/test/API/commands/expression/import-std-module/stack/TestStackFromStdModule.py
@@ -22,7 +22,7 @@
         self.runCmd("settings set target.import-std-module true")
 
         # Test std::stack functionality with a std::deque.
-        stack_type = "std::stack<C, std::deque<C, std::allocator<C> > >"
+        stack_type = "std::stack<C>"
         size_type = stack_type + "::size_type"
 
         self.expect_expr("s_deque", result_type=stack_type)
@@ -40,7 +40,7 @@
                          result_value="5")
 
         # Test std::stack functionality with a std::vector.
-        stack_type = "std::stack<C, std::vector<C, std::allocator<C> > >"
+        stack_type = "std::stack<C, std::vector<C> >"
         size_type = stack_type + "::size_type"
 
         self.expect_expr("s_vector", result_type=stack_type)
@@ -58,7 +58,7 @@
                          result_value="5")
 
         # Test std::stack functionality with a std::list.
-        stack_type = "std::stack<C, std::list<C, std::allocator<C> > >"
+        stack_type = "std::stack<C, std::list<C> >"
         size_type = stack_type + "::size_type"
         self.expect_expr("s_list", result_type=stack_type)
         self.expect("expr s_list.pop()")
diff --git a/lldb/test/API/commands/expression/import-std-module/unique_ptr-dbg-info-content/TestUniquePtrDbgInfoContent.py b/lldb/test/API/commands/expression/import-std-module/unique_ptr-dbg-info-content/TestUniquePtrDbgInfoContent.py
--- a/lldb/test/API/commands/expression/import-std-module/unique_ptr-dbg-info-content/TestUniquePtrDbgInfoContent.py
+++ b/lldb/test/API/commands/expression/import-std-module/unique_ptr-dbg-info-content/TestUniquePtrDbgInfoContent.py
@@ -25,7 +25,7 @@
 
         self.expect_expr(
             "s",
-            result_type="std::unique_ptr<Foo, std::default_delete<Foo> >",
+            result_type="std::unique_ptr<Foo>",
             result_children=[ValueCheck(children=[ValueCheck(value="3")])])
         self.expect_expr("s->a", result_type="int", result_value="3")
         self.expect_expr("s->a = 5", result_type="int", result_value="5")
diff --git a/lldb/test/API/commands/expression/import-std-module/unique_ptr/TestUniquePtrFromStdModule.py b/lldb/test/API/commands/expression/import-std-module/unique_ptr/TestUniquePtrFromStdModule.py
--- a/lldb/test/API/commands/expression/import-std-module/unique_ptr/TestUniquePtrFromStdModule.py
+++ b/lldb/test/API/commands/expression/import-std-module/unique_ptr/TestUniquePtrFromStdModule.py
@@ -25,7 +25,7 @@
 
         self.expect_expr(
             "s",
-            result_type="std::unique_ptr<int, std::default_delete<int> >",
+            result_type="std::unique_ptr<int>",
             result_summary="3",
             result_children=[ValueCheck(name="__value_")])
         self.expect_expr("*s", result_type="int", result_value="3")
diff --git a/lldb/test/API/commands/expression/import-std-module/vector-bool/TestVectorBoolFromStdModule.py b/lldb/test/API/commands/expression/import-std-module/vector-bool/TestVectorBoolFromStdModule.py
--- a/lldb/test/API/commands/expression/import-std-module/vector-bool/TestVectorBoolFromStdModule.py
+++ b/lldb/test/API/commands/expression/import-std-module/vector-bool/TestVectorBoolFromStdModule.py
@@ -20,7 +20,7 @@
                                           "// Set break point at this line.",
                                           lldb.SBFileSpec("main.cpp"))
 
-        vector_type = "std::vector<bool, std::allocator<bool> >"
+        vector_type = "std::vector<bool>"
         size_type = vector_type + "::size_type"
 
         self.runCmd("settings set target.import-std-module true")
diff --git a/lldb/test/API/commands/expression/import-std-module/vector-dbg-info-content/TestDbgInfoContentVectorFromStdModule.py b/lldb/test/API/commands/expression/import-std-module/vector-dbg-info-content/TestDbgInfoContentVectorFromStdModule.py
--- a/lldb/test/API/commands/expression/import-std-module/vector-dbg-info-content/TestDbgInfoContentVectorFromStdModule.py
+++ b/lldb/test/API/commands/expression/import-std-module/vector-dbg-info-content/TestDbgInfoContentVectorFromStdModule.py
@@ -23,7 +23,7 @@
 
         self.runCmd("settings set target.import-std-module true")
 
-        vector_type = "std::vector<Foo, std::allocator<Foo> >"
+        vector_type = "std::vector<Foo>"
         size_type = vector_type + "::size_type"
         value_type = vector_type + "::value_type"
         iterator = vector_type + "::iterator"
diff --git a/lldb/test/API/commands/expression/import-std-module/vector-of-vectors/TestVectorOfVectorsFromStdModule.py b/lldb/test/API/commands/expression/import-std-module/vector-of-vectors/TestVectorOfVectorsFromStdModule.py
--- a/lldb/test/API/commands/expression/import-std-module/vector-of-vectors/TestVectorOfVectorsFromStdModule.py
+++ b/lldb/test/API/commands/expression/import-std-module/vector-of-vectors/TestVectorOfVectorsFromStdModule.py
@@ -20,13 +20,9 @@
                                           "// Set break point at this line.",
                                           lldb.SBFileSpec("main.cpp"))
 
-        vector_type = "std::vector<int, std::allocator<int> >"
-        vector_of_vector_type = "std::vector<" + vector_type + \
-            ", std::allocator<std::vector<int, std::allocator<int> > > >"
-        size_type = (
-            "std::vector<std::vector<int, std::allocator<int> >, " +
-            "std::allocator<std::vector<int, std::allocator<int> > >" +
-            " >::size_type")
+        vector_type = "std::vector<int>"
+        vector_of_vector_type = "std::vector<" + vector_type + " >"
+        size_type = vector_of_vector_type + "::size_type"
         value_type = "std::__vector_base<int, std::allocator<int> >::value_type"
 
         self.runCmd("settings set target.import-std-module true")
@@ -35,13 +31,13 @@
             "a",
             result_type=vector_of_vector_type,
             result_children=[
-                ValueCheck(type="std::vector<int, std::allocator<int> >",
+                ValueCheck(type="std::vector<int>",
                            children=[
                                ValueCheck(value='1'),
                                ValueCheck(value='2'),
                                ValueCheck(value='3'),
                            ]),
-                ValueCheck(type="std::vector<int, std::allocator<int> >",
+                ValueCheck(type="std::vector<int>",
                            children=[
                                ValueCheck(value='3'),
                                ValueCheck(value='2'),
diff --git a/lldb/test/API/commands/expression/import-std-module/vector/TestVectorFromStdModule.py b/lldb/test/API/commands/expression/import-std-module/vector/TestVectorFromStdModule.py
--- a/lldb/test/API/commands/expression/import-std-module/vector/TestVectorFromStdModule.py
+++ b/lldb/test/API/commands/expression/import-std-module/vector/TestVectorFromStdModule.py
@@ -22,7 +22,7 @@
 
         self.runCmd("settings set target.import-std-module true")
 
-        vector_type = "std::vector<int, std::allocator<int> >"
+        vector_type = "std::vector<int>"
         size_type = vector_type + "::size_type"
         value_type = "std::__vector_base<int, std::allocator<int> >::value_type"
         iterator = vector_type + "::iterator"