[ASTMatchers] Add hasSideEffect() matcher.

[courbet]

Summary

Exposes Expr::HasSideEffects.

[courbet]

rebase

[aaron.ballman]

LGTM aside from a minor commenting request.

include/clang/ASTMatchers/ASTMatchers.h

4121

side effects. -> side effects other than producing a value, such as a calling a function, throwing an exception, or reading a volatile variable.

[courbet]

address comment

[courbet]

Thanks.

docs/LibASTMatchersReference.html

 <tr><td colspan="4" class="doc" id="isScoped0"><pre>Matches C++11 scoped enum declaration.
 
 Example matches Y (matcher = enumDecl(isScoped()))
 enum X {};
 enum class Y {};
 </pre></td></tr>
 
 
+<tr><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1Expr.html">Expr</a>&gt;</td><td class="name" onclick="toggle('hasSideEffects0')"><a name="hasSideEffects0Anchor">hasSideEffects</a></td><td></td></tr>
+<tr><td colspan="4" class="doc" id="hasSideEffects0"><pre>Matches expressions with potential side effects other than producing
+a value, such as a calling a function, throwing an exception, or reading a
+volatile variable.
+
+Given
+  void f(int&amp; a, int b, volatile int c) {
+    call();
+    a = 0;
+    a;
+    b;
+    c;
+  }
+expr(hasSideEffects())
+  matches 'call()', 'a = 0', 'c', but not '0', 'a', 'b'.
+</pre></td></tr>
+
+
 <tr><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1Expr.html">Expr</a>&gt;</td><td class="name" onclick="toggle('isInstantiationDependent0')"><a name="isInstantiationDependent0Anchor">isInstantiationDependent</a></td><td></td></tr>
 <tr><td colspan="4" class="doc" id="isInstantiationDependent0"><pre>Matches expressions that are instantiation-dependent even if it is
 neither type- nor value-dependent.
 
 In the following example, the expression sizeof(sizeof(T() + T()))
 is instantiation-dependent (since it involves a template parameter T),
 but is neither type- nor value-dependent, since the type of the inner
 sizeof is known (std::size_t) and therefore the size of the outer

include/clang/ASTMatchers/ASTMatchers.h

 AST_MATCHER_P(IfStmt, hasConditionVariableStatement,
               internal::Matcher<DeclStmt>, InnerMatcher) {
   const DeclStmt* const DeclarationStatement =
     Node.getConditionVariableDeclStmt();
   return DeclarationStatement != nullptr &&
          InnerMatcher.matches(*DeclarationStatement, Finder, Builder);
 }
 
+/// \brief Matches expressions with potential side effects other than producing
+/// a value, such as a calling a function, throwing an exception, or reading a
+/// volatile variable.
+///
+/// Given
+/// \code
+///   void f(int& a, int b, volatile int c) {
+///     call();
+///     a = 0;
+///     a;
+///     b;
+///     c;
+///   }
+/// \endcode
+/// expr(hasSideEffects())
+///   matches 'call()', 'a = 0', 'c', but not '0', 'a', 'b'.
+AST_MATCHER(Expr, hasSideEffects) {
+  return Node.HasSideEffects(Finder->getASTContext());
+}
+
 /// Matches the index expression of an array subscript expression.
 ///
 /// Given
 /// \code
 ///   int i[5];
 ///   void f() { i[1] = 42; }
 /// \endcode
 /// arraySubscriptExpression(hasIndex(integerLiteral()))

lib/ASTMatchers/Dynamic/Registry.cpp

RegistryMaps::RegistryMaps() {
   REGISTER_MATCHER(hasQualifier);
   REGISTER_MATCHER(hasRangeInit);
   REGISTER_MATCHER(hasReceiver);
   REGISTER_MATCHER(hasReceiverType);
   REGISTER_MATCHER(hasReplacementType);
   REGISTER_MATCHER(hasReturnValue);
   REGISTER_MATCHER(hasRHS);
   REGISTER_MATCHER(hasSelector);
+  REGISTER_MATCHER(hasSideEffects);
   REGISTER_MATCHER(hasSingleDecl);
   REGISTER_MATCHER(hasSize);
   REGISTER_MATCHER(hasSizeExpr);
   REGISTER_MATCHER(hasSourceExpression);
   REGISTER_MATCHER(hasSpecializedTemplate);
   REGISTER_MATCHER(hasStaticStorageDuration);
   REGISTER_MATCHER(hasSyntacticForm);
   REGISTER_MATCHER(hasTargetDecl);

unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp

 TEST(Matcher, isMain) {
   EXPECT_TRUE(
     matches("int main() {}", functionDecl(isMain())));
 
   EXPECT_TRUE(
     notMatches("int main2() {}", functionDecl(isMain())));
 }
 
+TEST(Matcher, hasSideEffects) {
+  EXPECT_TRUE(matches("void call();"
+                      "void f() { call(); }",
+                      expr(hasSideEffects())));
+  EXPECT_TRUE(matches("void f(int& a) { a = 0; }", expr(hasSideEffects())));
+  EXPECT_TRUE(
+      matches("void f(volatile int a) { (void)a; }", expr(hasSideEffects())));
+
+  EXPECT_TRUE(notMatches("void call();"
+                         "void f() { }",
+                         expr(hasSideEffects())));
+  EXPECT_TRUE(
+      notMatches("void f(int& a) { (void)a; }", expr(hasSideEffects())));
+  EXPECT_TRUE(notMatches("void f(int a) { (void)a; }", expr(hasSideEffects())));
+}
+
 } // namespace ast_matchers
 } // namespace clang