Index: clang/include/clang/Basic/DiagnosticGroups.td
===================================================================
--- clang/include/clang/Basic/DiagnosticGroups.td
+++ clang/include/clang/Basic/DiagnosticGroups.td
@@ -693,6 +693,7 @@
 def GNUZeroLineDirective : DiagGroup<"gnu-zero-line-directive">;
 def GNUZeroVariadicMacroArguments : DiagGroup<"gnu-zero-variadic-macro-arguments">;
 def Fallback : DiagGroup<"fallback">;
+def MisleadingIndentation : DiagGroup<"misleading-indentation">;
 
 // This covers both the deprecated case (in C++98)
 // and the extension case (in C++11 onwards).
@@ -861,7 +862,8 @@
     PrivateExtern,
     SelTypeCast,
     ExternCCompat,
-    UserDefinedWarnings
+    UserDefinedWarnings,
+    MisleadingIndentation
  ]>;
 
 // Thread Safety warnings
Index: clang/include/clang/Basic/DiagnosticParseKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticParseKinds.td
+++ clang/include/clang/Basic/DiagnosticParseKinds.td
@@ -61,6 +61,12 @@
   "remove unnecessary ';' to silence this warning">,
   InGroup<ExtraSemiStmt>, DefaultIgnore;
 
+def warn_misleading_indentation : Warning<
+  "this indention is missleading; this statement is not part of the previous"
+  " '%0'">, InGroup<MisleadingIndentation>, DefaultIgnore;
+def note_previous_statement : Note<
+  "previous statement is here">;
+
 def ext_thread_before : Extension<"'__thread' before '%0'">;
 def ext_keyword_as_ident : ExtWarn<
   "keyword '%0' will be made available as an identifier "
Index: clang/lib/Parse/ParseStmt.cpp
===================================================================
--- clang/lib/Parse/ParseStmt.cpp
+++ clang/lib/Parse/ParseStmt.cpp
@@ -1191,6 +1191,19 @@
   return false;
 }
 
+static void MaybeDiagnoseMisleadingIndentation(Parser &P, Token Tok,
+                                                SourceLocation PrevLoc,
+                                                SourceLocation StmtLoc,
+                                                const char *StmtName) {
+  SourceManager& SM = P.getPreprocessor().getSourceManager();
+  unsigned PrevStmtColNum = SM.getSpellingColumnNumber(PrevLoc);
+  unsigned CurStmtColNum = SM.getSpellingColumnNumber(Tok.getLocation());
+  if (PrevStmtColNum != 0 && CurStmtColNum != 0 &&
+      PrevStmtColNum <= CurStmtColNum) {
+    P.Diag(Tok.getLocation(), diag::warn_misleading_indentation) << StmtName;
+    P.Diag(StmtLoc, diag::note_previous_statement);
+  }
+}
 
 /// ParseIfStatement
 ///       if-statement: [C99 6.8.4.1]
@@ -1281,6 +1294,9 @@
   // Pop the 'if' scope if needed.
   InnerScope.Exit();
 
+  if (Tok.isNot(tok::kw_else))
+    MaybeDiagnoseMisleadingIndentation(*this, Tok, ThenStmtLoc, IfLoc, "if");
+
   // If it has an else, parse it.
   SourceLocation ElseLoc;
   SourceLocation ElseStmtLoc;
@@ -1313,6 +1329,9 @@
 
     // Pop the 'else' scope if needed.
     InnerScope.Exit();
+    if (ElseStmt.isUsable())
+      MaybeDiagnoseMisleadingIndentation(
+          *this, Tok, ElseStmt.get()->getBeginLoc(), ElseLoc, "else");
   } else if (Tok.is(tok::code_completion)) {
     Actions.CodeCompleteAfterIf(getCurScope());
     cutOffParsing();
@@ -1491,6 +1510,10 @@
   InnerScope.Exit();
   WhileScope.Exit();
 
+  if (Body.isUsable())
+    MaybeDiagnoseMisleadingIndentation(*this, Tok, Body.get()->getBeginLoc(),
+                                        WhileLoc, "while");
+
   if (Cond.isInvalid() || Body.isInvalid())
     return StmtError();
 
@@ -1927,6 +1950,10 @@
   // Leave the for-scope.
   ForScope.Exit();
 
+  if (Body.isUsable())
+    MaybeDiagnoseMisleadingIndentation(*this, Tok, Body.get()->getBeginLoc(),
+                                        ForLoc, "for");
+
   if (Body.isInvalid())
     return StmtError();
 
Index: clang/test/SemaCXX/warn-misleanding-indentation.cpp
===================================================================
--- /dev/null
+++ clang/test/SemaCXX/warn-misleanding-indentation.cpp
@@ -0,0 +1,59 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -Wmisleading-indentation -DWITH_WARN %s
+// RUN: %clang_cc1 -fsyntax-only -verify -Wall -DWITH_WARN %s
+// RUN: %clang_cc1 -fsyntax-only -verify -Wall -Wno-misleading-indentation %s
+
+#ifndef WITH_WARN
+// expected-no-diagnostics
+#endif
+
+void f0(int i) {
+  if (i)
+#ifdef WITH_WARN
+// expected-note@-2 {{here}}
+#endif
+    i = i + 1;
+    i *= 2;
+#ifdef WITH_WARN
+// expected-warning@-2 {{indention is missleading}}
+#endif
+  return;
+}
+
+void f1(int i) {
+  for (;i;)
+#ifdef WITH_WARN
+// expected-note@-2 {{here}}
+#endif
+    i = i + 1;
+     i *= 2;
+#ifdef WITH_WARN
+// expected-warning@-2 {{indention is missleading}}
+#endif
+  return;
+}
+
+void f2(int i) {
+  while (i)
+#ifdef WITH_WARN
+// expected-note@-2 {{here}}
+#endif
+    i = i + 1; i *= 2;
+#ifdef WITH_WARN
+// expected-warning@-2 {{indention is missleading}}
+#endif
+  return;
+}
+
+void f3(int i) {
+  if (i)
+    i = i + 1;
+  else
+#ifdef WITH_WARN
+// expected-note@-2 {{here}}
+#endif
+    i *= 2;
+    return;
+#ifdef WITH_WARN
+// expected-warning@-2 {{indention is missleading}}
+#endif
+}