[PATCH] Add new warning to -Wparentheses for mixing overloaded shift operators and comparison operators

[Richard Trieu]

  Add some whitespace to DiagnoseShiftCompare() for better readability.

http://llvm-reviews.chandlerc.com/D650

CHANGE SINCE LAST DIFF
  http://llvm-reviews.chandlerc.com/D650?vs=1577&id=1658#toc

Files:
  lib/Sema/SemaExpr.cpp
  test/Sema/parentheses.cpp
  include/clang/Basic/DiagnosticGroups.td
  include/clang/Basic/DiagnosticSemaKinds.td

Index: lib/Sema/SemaExpr.cpp
===================================================================
--- lib/Sema/SemaExpr.cpp
+++ lib/Sema/SemaExpr.cpp
@@ -8819,6 +8819,33 @@
   }
 }
 
+static void DiagnoseShiftCompare(Sema &S, SourceLocation OpLoc,
+                                 Expr *LHSExpr, Expr *RHSExpr) {
+  CXXOperatorCallExpr *OCE = dyn_cast<CXXOperatorCallExpr>(LHSExpr);
+  if (!OCE)
+    return;
+
+  FunctionDecl *FD = OCE->getDirectCallee();
+  if (!FD || !FD->isOverloadedOperator())
+    return;
+
+  OverloadedOperatorKind Kind = FD->getOverloadedOperator();
+  if (Kind != OO_LessLess && Kind != OO_GreaterGreater)
+    return;
+
+  S.Diag(OpLoc, diag::warn_overloaded_shift_in_comparison)
+      << LHSExpr->getSourceRange() << RHSExpr->getSourceRange()
+      << (Kind == OO_LessLess);
+  SuggestParentheses(S, OpLoc,
+                     S.PDiag(diag::note_evaluate_comparison_first),
+                     SourceRange(OCE->getArg(1)->getLocStart(),
+                                 RHSExpr->getLocEnd()));
+  SuggestParentheses(S, OCE->getOperatorLoc(),
+                     S.PDiag(diag::note_precedence_silence)
+                         << (Kind == OO_LessLess ? "<<" : ">>"),
+                     OCE->getSourceRange());
+}
+
 /// DiagnoseBinOpPrecedence - Emit warnings for expressions with tricky
 /// precedence.
 static void DiagnoseBinOpPrecedence(Sema &Self, BinaryOperatorKind Opc,
@@ -8847,6 +8874,11 @@
     DiagnoseAdditionInShift(Self, OpLoc, LHSExpr, Shift);
     DiagnoseAdditionInShift(Self, OpLoc, RHSExpr, Shift);
   }
+
+  // Warn on overloaded shift operators and comparisons, such as:
+  // cout << 5 == 4;
+  if (BinaryOperator::isComparisonOp(Opc))
+    DiagnoseShiftCompare(Self, OpLoc, LHSExpr, RHSExpr);
 }
 
 // Binary Operators.  'Tok' is the token for the operator.
Index: test/Sema/parentheses.cpp
===================================================================
--- test/Sema/parentheses.cpp
+++ test/Sema/parentheses.cpp
@@ -29,6 +29,12 @@
   (void)(s << b ? "foo" : "bar"); // expected-warning {{operator '?:' has lower precedence than '<<'}} \
                                   // expected-note {{place parentheses around the '?:' expression to evaluate it first}} \
                                   // expected-note {{place parentheses around the '<<' expression to silence this warning}}
+  (void)(s << 5 == 1); // expected-warning {{overloaded operator << has lower precedence than comparison operator}} \
+                       // expected-note {{place parentheses around the '<<' expression to silence this warning}} \
+                       // expected-note {{place parentheses around comparison expression to evaluate it first}}
+  (void)(s >> 5 == 1); // expected-warning {{overloaded operator >> has lower precedence than comparison operator}} \
+                       // expected-note {{place parentheses around the '>>' expression to silence this warning}} \
+                       // expected-note {{place parentheses around comparison expression to evaluate it first}}
 }
 
 struct S {
Index: include/clang/Basic/DiagnosticGroups.td
===================================================================
--- include/clang/Basic/DiagnosticGroups.td
+++ include/clang/Basic/DiagnosticGroups.td
@@ -122,6 +122,7 @@
 def BitwiseOpParentheses: DiagGroup<"bitwise-op-parentheses">;
 def LogicalOpParentheses: DiagGroup<"logical-op-parentheses">;
 def ShiftOpParentheses: DiagGroup<"shift-op-parentheses">;
+def OverloadedShiftOpParentheses: DiagGroup<"overloaded-shift-op-parentheses">;
 def DanglingElse: DiagGroup<"dangling-else">;
 def DanglingField : DiagGroup<"dangling-field">;
 def DistributedObjectModifiers : DiagGroup<"distributed-object-modifiers">;
@@ -352,6 +353,7 @@
                             [LogicalOpParentheses,
                              BitwiseOpParentheses,
                              ShiftOpParentheses,
+                             OverloadedShiftOpParentheses,
                              ParenthesesOnEquality,
                              DanglingElse]>;
 
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -4025,6 +4025,13 @@
 def warn_logical_and_in_logical_or : Warning<
   "'&&' within '||'">, InGroup<LogicalOpParentheses>;
 
+def warn_overloaded_shift_in_comparison :Warning<
+  "overloaded operator %select{>>|<<}0 has lower precedence than "
+  "comparison operator">,
+  InGroup<OverloadedShiftOpParentheses>;
+def note_evaluate_comparison_first :Note<
+  "place parentheses around comparison expression to evaluate it first">;
+
 def warn_addition_in_bitshift : Warning<
   "operator '%0' has lower precedence than '%1'; "
   "'%1' will be evaluated first">, InGroup<ShiftOpParentheses>;
-------------- next part --------------
A non-text attachment was scrubbed...
Name: D650.2.patch
Type: text/x-patch
Size: 4879 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20130416/1821a1cb/attachment.bin>