Index: include/clang/Basic/DiagnosticLexKinds.td
===================================================================
--- include/clang/Basic/DiagnosticLexKinds.td
+++ include/clang/Basic/DiagnosticLexKinds.td
@@ -422,8 +422,10 @@
   "#pragma hdrstop filename not supported, "
   "/Fp can be used to specify precompiled header filename">,
   InGroup<ClangClPch>;
-def err_pp_file_not_found_not_fatal : Error<
+def err_pp_file_not_found_angled_include_not_fatal : Error<
   "'%0' file not found with <angled> include; use \"quotes\" instead">;
+def err_pp_file_not_found_typo_not_fatal
+    : Error<"'%0' file not found, did you mean '%1'?">;
 def err_pp_error_opening_file : Error<
   "error opening file '%0': %1">, DefaultFatal;
 def err_pp_empty_filename : Error<"empty filename">;
Index: lib/Lex/PPDirectives.cpp
===================================================================
--- lib/Lex/PPDirectives.cpp
+++ lib/Lex/PPDirectives.cpp
@@ -1879,12 +1879,40 @@
             Callbacks ? &RelativePath : nullptr, &SuggestedModule, &IsMapped);
         if (File) {
           SourceRange Range(FilenameTok.getLocation(), CharEnd);
-          Diag(FilenameTok, diag::err_pp_file_not_found_not_fatal) <<
+          Diag(FilenameTok, diag::err_pp_file_not_found_angled_include_not_fatal) <<
             Filename <<
             FixItHint::CreateReplacement(Range, "\"" + Filename.str() + "\"");
         }
       }
 
+      // Check for likely typos due to leading or trailing non-isAlphanumeric
+      // characters
+      if (!File) {
+        StringRef OriginalFilename = Filename;
+        while (!isAlphanumeric(Filename.front())) {
+          Filename = Filename.drop_front();
+        }
+        while (!isAlphanumeric(Filename.back())) {
+          Filename = Filename.drop_back();
+        }
+
+        File = LookupFile(
+            FilenameLoc,
+            LangOpts.MSVCCompat ? NormalizedPath.c_str() : Filename, isAngled,
+            LookupFrom, LookupFromFile, CurDir,
+            Callbacks ? &SearchPath : nullptr,
+            Callbacks ? &RelativePath : nullptr, &SuggestedModule, &IsMapped);
+        if (File) {
+          SourceRange Range(FilenameTok.getLocation(), CharEnd);
+          auto Hint = isAngled ? FixItHint::CreateReplacement(
+                                     Range, "<" + Filename.str() + ">")
+                               : FixItHint::CreateReplacement(
+                                     Range, "\"" + Filename.str() + "\"");
+          Diag(FilenameTok, diag::err_pp_file_not_found_typo_not_fatal)
+              << OriginalFilename << Filename << Hint;
+        }
+      }
+
       // If the file is still not found, just go with the vanilla diagnostic
       if (!File)
         Diag(FilenameTok, diag::err_pp_file_not_found) << Filename