Index: clang/lib/Format/TokenAnnotator.cpp
===================================================================
--- clang/lib/Format/TokenAnnotator.cpp
+++ clang/lib/Format/TokenAnnotator.cpp
@@ -1915,6 +1915,13 @@
     if (Tok.Next->isOneOf(tok::identifier, tok::kw_this))
       return true;
 
+    if (Tok.Next->is(tok::l_paren) &&
+        !(Tok.Previous && Tok.Previous->is(tok::identifier) &&
+          Tok.Previous->Previous &&
+          Tok.Previous->Previous->isOneOf(tok::arrowstar, tok::arrow,
+                                          tok::star)))
+      return true;
+
     if (!Tok.Next->Next)
       return false;
 
Index: clang/unittests/Format/FormatTest.cpp
===================================================================
--- clang/unittests/Format/FormatTest.cpp
+++ clang/unittests/Format/FormatTest.cpp
@@ -11989,6 +11989,20 @@
                "  do_something((int) i);\n"
                "} while (something( ));",
                Spaces);
+
+  verifyFormat("size_t idx = (size_t) (ptr - ((char *) file));", Spaces);
+  verifyFormat("size_t idx = (size_t) a;", Spaces);
+  verifyFormat("size_t idx = (size_t) (a - 1);", Spaces);
+  verifyFormat("size_t idx = (a->*foo)(a - 1);", Spaces);
+  verifyFormat("size_t idx = (a->foo)(a - 1);", Spaces);
+  verifyFormat("size_t idx = (*foo)(a - 1);", Spaces);
+  Spaces.SpaceAfterCStyleCast = false;
+  verifyFormat("size_t idx = (size_t)(ptr - ((char *)file));", Spaces);
+  verifyFormat("size_t idx = (size_t)a;", Spaces);
+  verifyFormat("size_t idx = (size_t)(a - 1);", Spaces);
+  verifyFormat("size_t idx = (a->*foo)(a - 1);", Spaces);
+  verifyFormat("size_t idx = (a->foo)(a - 1);", Spaces);
+  verifyFormat("size_t idx = (*foo)(a - 1);", Spaces);
 }
 
 TEST_F(FormatTest, ConfigurableSpacesInSquareBrackets) {