[ASTMatchers] Add isAssignmentOperator matcher

Adding a matcher for BinaryOperator and cxxOperatorCallExpr to be able to
decide whether it is any kind of assignment operator or not. This would be
useful since allows us to easily detect assignments via matchers for static
analysis (Tidy, SA) purposes.

Differential Revision: https://reviews.llvm.org/D44893

llvm-svn: 328618

clang/docs/LibASTMatchersReference.html

@@ -1926,6 +1926,19 @@ <h2 id="narrowing-matchers">Narrowing Matchers</h2>
 </pre></td></tr>
 
 
+<tr><td>Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1BinaryOperator.html">BinaryOperator</a>&gt;</td><td class="name" onclick="toggle('isAssignmentOperator0')"><a name="isAssignmentOperator0Anchor">isAssignmentOperator</a></td></tr>
+<tr><td colspan="4" class="doc" id="isAssignmentOperator0"><pre>Matches all kinds of assignment operators.
+
+Example 1: matches a += b (matcher = binaryOperator(isAssignmentOperator()))
+  if (a == b)
+    a += b;
+
+Example 2: matches s1 = s2 (matcher = cxxOperatorCallExpr(isAssignmentOperator()))
+  struct S { S& operator=(const S&); };
+  void x() { S s1, s2; s1 = s2; })
+</pre></td></tr>
+
+
 <tr><td>Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1CXXBoolLiteralExpr.html">CXXBoolLiteralExpr</a>&gt;</td><td class="name" onclick="toggle('equals5')"><a name="equals5Anchor">equals</a></td><td>bool Value</td></tr>
 <tr><td colspan="4" class="doc" id="equals5"><pre></pre></td></tr>
 
@@ -2306,6 +2319,19 @@ <h2 id="narrowing-matchers">Narrowing Matchers</h2>
 </pre></td></tr>
 
 
+<tr><td>Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1CXXOperatorCallExpr.html">CXXOperatorCallExpr</a>&gt;</td><td class="name" onclick="toggle('isAssignmentOperator1')"><a name="isAssignmentOperator1Anchor">isAssignmentOperator</a></td></tr>
+<tr><td colspan="4" class="doc" id="isAssignmentOperator1"><pre>Matches all kinds of assignment operators.
+
+Example 1: matches a += b (matcher = binaryOperator(isAssignmentOperator()))
+  if (a == b)
+    a += b;
+
+Example 2: matches s1 = s2 (matcher = cxxOperatorCallExpr(isAssignmentOperator()))
+  struct S { S& operator=(const S&); };
+  void x() { S s1, s2; s1 = s2; })
+</pre></td></tr>
+
+
 <tr><td>Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1CXXRecordDecl.html">CXXRecordDecl</a>&gt;</td><td class="name" onclick="toggle('hasDefinition0')"><a name="hasDefinition0Anchor">hasDefinition</a></td><td></td></tr>
 <tr><td colspan="4" class="doc" id="hasDefinition0"><pre>Matches a class declaration that is defined.
 

clang/include/clang/ASTMatchers/ASTMatchers.h

@@ -4003,6 +4003,26 @@ AST_POLYMORPHIC_MATCHER_P(hasOperatorName,
   return Name == Node.getOpcodeStr(Node.getOpcode());
 }
 
+/// \brief Matches on all kinds of assignment operators.
+///
+/// Example 1: matches a += b (matcher = binaryOperator(isAssignmentOperator()))
+/// \code
+///   if (a == b)
+///     a += b;
+/// \endcode
+///
+/// Example 2: matches s1 = s2
+///            (matcher = cxxOperatorCallExpr(isAssignmentOperator()))
+/// \code
+///   struct S { S& operator=(const S&); };
+///   void x() { S s1, s2; s1 = s2; })
+/// \endcode
+AST_POLYMORPHIC_MATCHER(isAssignmentOperator,
+                        AST_POLYMORPHIC_SUPPORTED_TYPES(BinaryOperator,
+                                                        CXXOperatorCallExpr)) {
+  return Node.isAssignmentOp();
+}
+
 /// \brief Matches the left hand side of binary operator expressions.
 ///
 /// Example matches a (matcher = binaryOperator(hasLHS()))

clang/lib/ASTMatchers/Dynamic/Registry.cpp

@@ -322,6 +322,7 @@ RegistryMaps::RegistryMaps() {
   REGISTER_MATCHER(isAnyPointer);
   REGISTER_MATCHER(isArray);
   REGISTER_MATCHER(isArrow);
+  REGISTER_MATCHER(isAssignmentOperator);
   REGISTER_MATCHER(isBaseInitializer);
   REGISTER_MATCHER(isBitField);
   REGISTER_MATCHER(isCatchAll);

clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp

@@ -2139,5 +2139,20 @@ TEST(HasTrailingReturn, MatchesLambdaTrailingReturn) {
           functionDecl(hasTrailingReturn())));
 }
 
+TEST(IsAssignmentOperator, Basic) {
+  StatementMatcher BinAsgmtOperator = binaryOperator(isAssignmentOperator());
+  StatementMatcher CXXAsgmtOperator =
+      cxxOperatorCallExpr(isAssignmentOperator());
+
+  EXPECT_TRUE(matches("void x() { int a; a += 1; }", BinAsgmtOperator));
+  EXPECT_TRUE(matches("void x() { int a; a = 2; }", BinAsgmtOperator));
+  EXPECT_TRUE(matches("void x() { int a; a &= 3; }", BinAsgmtOperator));
+  EXPECT_TRUE(matches("struct S { S& operator=(const S&); };"
+                      "void x() { S s1, s2; s1 = s2; }",
+                      CXXAsgmtOperator));
+  EXPECT_TRUE(
+      notMatches("void x() { int a; if(a == 0) return; }", BinAsgmtOperator));
+}
+
 } // namespace ast_matchers
 } // namespace clang