Index: clang/lib/Parse/ParseCXXInlineMethods.cpp
===================================================================
--- clang/lib/Parse/ParseCXXInlineMethods.cpp
+++ clang/lib/Parse/ParseCXXInlineMethods.cpp
@@ -452,13 +452,14 @@
     CXXMethodDecl *Method;
     if (FunctionTemplateDecl *FunTmpl
           = dyn_cast<FunctionTemplateDecl>(LM.Method))
-      Method = cast<CXXMethodDecl>(FunTmpl->getTemplatedDecl());
+      Method = dyn_cast<CXXMethodDecl>(FunTmpl->getTemplatedDecl());
     else
-      Method = cast<CXXMethodDecl>(LM.Method);
+      Method = dyn_cast<CXXMethodDecl>(LM.Method);
 
-    Sema::CXXThisScopeRAII ThisScope(Actions, Method->getParent(),
-                                     Method->getMethodQualifiers(),
-                                     getLangOpts().CPlusPlus11);
+    Sema::CXXThisScopeRAII ThisScope(
+        Actions, Method ? Method->getParent() : nullptr,
+        Method ? Method->getMethodQualifiers() : Qualifiers{},
+        Method && getLangOpts().CPlusPlus11);
 
     // Parse the exception-specification.
     SourceRange SpecificationRange;
Index: clang/test/Parser/cxx1z-class-template-argument-deduction.cpp
===================================================================
--- clang/test/Parser/cxx1z-class-template-argument-deduction.cpp
+++ clang/test/Parser/cxx1z-class-template-argument-deduction.cpp
@@ -230,3 +230,21 @@
 
   template<int ...N> struct Z { Y<X(N)...> y; };
 }
+
+namespace PR49735 {
+// Ensure that we do not crash when parsing code which looks like an invalid
+// deduction guide declaration.
+template<class> struct B; // expected-note 2{{template is declared here}}
+struct A1 {
+  B() noexcept(false); // expected-error {{deduction guide must be declared in the same scope as template 'PR49735::B'}} \
+                       // expected-error {{deduction guide declaration without trailing return type}}
+};
+
+struct A2 {
+  template <typename Ty> // expected-note {{non-deducible template parameter 'Ty'}}
+  B() noexcept(false); // expected-error {{deduction guide must be declared in the same scope as template 'PR49735::B'}} \
+                       // expected-error {{deduction guide template contains a template parameter that cannot be deduced}} \
+                       // expected-error {{deduction guide declaration without trailing return type}}
+};
+
+}