diff --git a/clang/docs/LibASTMatchersReference.html b/clang/docs/LibASTMatchersReference.html
--- a/clang/docs/LibASTMatchersReference.html
+++ b/clang/docs/LibASTMatchersReference.html
@@ -4671,6 +4671,23 @@
 Usable as: Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1FunctionDecl.html">FunctionDecl</a>&gt;, Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1VarDecl.html">VarDecl</a>&gt;, Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1CXXRecordDecl.html">CXXRecordDecl</a>&gt;
 </pre></td></tr>
 
+
+<tr><td>Matcher&lt;clang::ParmVarDecl&gt;</td><td class="name" onclick="toggle('isAtPosition0')"><a name="isAtPosition0Anchor">isAtPosition</a></td><td>unsigned N</td></tr>
+<tr><td colspan="4" class="doc" id="isAtPosition0"><pre>Matches the ParmVarDecl nodes that are at the N'th position in the parameter
+list. The parameter list could be that of either a block, function, or
+objc-method.
+
+
+Given
+
+void f(int a, int b, int c) {
+}
+
+``parmVarDecl(isAtPosition(0))`` matches ``int a``.
+
+``parmVarDecl(isAtPosition(1))`` matches ``int b``.
+</pre></td></tr>
+
 <!--END_NARROWING_MATCHERS -->
 </table>
 
diff --git a/clang/include/clang/ASTMatchers/ASTMatchers.h b/clang/include/clang/ASTMatchers/ASTMatchers.h
--- a/clang/include/clang/ASTMatchers/ASTMatchers.h
+++ b/clang/include/clang/ASTMatchers/ASTMatchers.h
@@ -4257,6 +4257,34 @@
   return Matched;
 }
 
+/// Matches the ParmVarDecl nodes that are at the N'th position in the parameter
+/// list. The parameter list could be that of either a block, function, or
+/// objc-method.
+///
+///
+/// Given
+///
+/// \code
+/// void f(int a, int b, int c) {
+/// }
+/// \endcode
+///
+/// ``parmVarDecl(isAtPosition(0))`` matches ``int a``.
+///
+/// ``parmVarDecl(isAtPosition(1))`` matches ``int b``.
+AST_MATCHER_P(clang::ParmVarDecl, isAtPosition, unsigned, N) {
+  const clang::DeclContext *Context = Node.getParentFunctionOrMethod();
+
+  if (const auto *Decl = dyn_cast_or_null<FunctionDecl>(Context))
+    return N < Decl->param_size() && Decl->getParamDecl(N) == &Node;
+  if (const auto *Decl = dyn_cast_or_null<BlockDecl>(Context))
+    return N < Decl->param_size() && Decl->getParamDecl(N) == &Node;
+  if (const auto *Decl = dyn_cast_or_null<ObjCMethodDecl>(Context))
+    return N < Decl->param_size() && Decl->getParamDecl(N) == &Node;
+
+  return false;
+}
+
 /// Matches any parameter of a function or an ObjC method declaration or a
 /// block.
 ///
diff --git a/clang/lib/ASTMatchers/Dynamic/Registry.cpp b/clang/lib/ASTMatchers/Dynamic/Registry.cpp
--- a/clang/lib/ASTMatchers/Dynamic/Registry.cpp
+++ b/clang/lib/ASTMatchers/Dynamic/Registry.cpp
@@ -219,6 +219,7 @@
   REGISTER_MATCHER(floatLiteral);
   REGISTER_MATCHER(forEach);
   REGISTER_MATCHER(forEachArgumentWithParam);
+  REGISTER_MATCHER(isAtPosition);
   REGISTER_MATCHER(forEachConstructorInitializer);
   REGISTER_MATCHER(forEachDescendant);
   REGISTER_MATCHER(forEachOverridden);
diff --git a/clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp b/clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp
--- a/clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp
+++ b/clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp
@@ -2643,6 +2643,45 @@
                       parmVarDecl(hasDefaultArgument())));
 }
 
+TEST(IsAtPosition, Basic) {
+  EXPECT_TRUE(matches("void x(int a, int b) {}", parmVarDecl(isAtPosition(1))));
+  EXPECT_TRUE(matches("void x(int a, int b) {}", parmVarDecl(isAtPosition(0))));
+  EXPECT_TRUE(matches("void x(int a, int b) {}", parmVarDecl(isAtPosition(1))));
+  EXPECT_TRUE(notMatches("void x(int val) {}", parmVarDecl(isAtPosition(1))));
+}
+
+TEST(IsAtPosition, FunctionDecl) {
+  EXPECT_TRUE(matches("void x(int a);", parmVarDecl(isAtPosition(0))));
+  EXPECT_TRUE(matches("void x(int a, int b);", parmVarDecl(isAtPosition(0))));
+  EXPECT_TRUE(matches("void x(int a, int b);", parmVarDecl(isAtPosition(1))));
+  EXPECT_TRUE(notMatches("void x(int val);", parmVarDecl(isAtPosition(1))));
+}
+
+TEST(IsAtPosition, Lambda) {
+  EXPECT_TRUE(
+      matches("void x() { [](int a) {};  }", parmVarDecl(isAtPosition(0))));
+  EXPECT_TRUE(matches("void x() { [](int a, int b) {}; }",
+                      parmVarDecl(isAtPosition(0))));
+  EXPECT_TRUE(matches("void x() { [](int a, int b) {}; }",
+                      parmVarDecl(isAtPosition(1))));
+  EXPECT_TRUE(
+      notMatches("void x() { [](int val) {}; }", parmVarDecl(isAtPosition(1))));
+}
+
+TEST(IsAtPosition, BlockDecl) {
+  EXPECT_TRUE(matchesObjC(
+      "void func()  { void (^my_block)(int arg) = ^void(int arg) {}; } ",
+      parmVarDecl(isAtPosition(0))));
+
+  EXPECT_TRUE(matchesObjC("void func()  { void (^my_block)(int x, int y) = "
+                          "^void(int x, int y) {}; } ",
+                          parmVarDecl(isAtPosition(1))));
+
+  EXPECT_TRUE(notMatchesObjC(
+      "void func()  { void (^my_block)(int arg) = ^void(int arg) {}; } ",
+      parmVarDecl(isAtPosition(1))));
+}
+
 TEST(IsArray, Basic) {
   EXPECT_TRUE(matches("struct MyClass {}; MyClass *p1 = new MyClass[10];",
                       cxxNewExpr(isArray())));