[ASTMatchers][NFC] integerLiteral(): Mention negative integers in

documentation.

Trying to match integerLiteral(-1) will silently fail, because an numeric
literal is always positive.
- Update the documentation to explain how to match negative numeric
  literals.
- Add a unit test.

Differential Revision: https://reviews.llvm.org/D35196

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@307663 91177308-0d34-0410-b5e6-96231b3b80d8

docs/LibASTMatchersReference.html

@@ -1872,6 +1872,14 @@ <h2 id="narrowing-matchers">Narrowing Matchers</h2>
 integerLiteral(equals(42))
   matches 42
 
+Note that you cannot directly match a negative numeric literal because the
+minus sign is not part of the literal: It is a unary operator whose operand
+is the positive numeric literal. Instead, you must use a unaryOperator()
+matcher to match the minus sign:
+
+unaryOperator(hasOperatorName("-"),
+              hasUnaryOperand(integerLiteral(equals(13))))
+
 Usable as: Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1CharacterLiteral.html">CharacterLiteral</a>&gt;, Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1CXXBoolLiteralExpr.html">CXXBoolLiteralExpr</a>&gt;,
            Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1FloatingLiteral.html">FloatingLiteral</a>&gt;, Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1IntegerLiteral.html">IntegerLiteral</a>&gt;
 </pre></td></tr>
@@ -2327,6 +2335,14 @@ <h2 id="narrowing-matchers">Narrowing Matchers</h2>
 integerLiteral(equals(42))
   matches 42
 
+Note that you cannot directly match a negative numeric literal because the
+minus sign is not part of the literal: It is a unary operator whose operand
+is the positive numeric literal. Instead, you must use a unaryOperator()
+matcher to match the minus sign:
+
+unaryOperator(hasOperatorName("-"),
+              hasUnaryOperand(integerLiteral(equals(13))))
+
 Usable as: Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1CharacterLiteral.html">CharacterLiteral</a>&gt;, Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1CXXBoolLiteralExpr.html">CXXBoolLiteralExpr</a>&gt;,
            Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1FloatingLiteral.html">FloatingLiteral</a>&gt;, Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1IntegerLiteral.html">IntegerLiteral</a>&gt;
 </pre></td></tr>
@@ -2583,6 +2599,14 @@ <h2 id="narrowing-matchers">Narrowing Matchers</h2>
 integerLiteral(equals(42))
   matches 42
 
+Note that you cannot directly match a negative numeric literal because the
+minus sign is not part of the literal: It is a unary operator whose operand
+is the positive numeric literal. Instead, you must use a unaryOperator()
+matcher to match the minus sign:
+
+unaryOperator(hasOperatorName("-"),
+              hasUnaryOperand(integerLiteral(equals(13))))
+
 Usable as: Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1CharacterLiteral.html">CharacterLiteral</a>&gt;, Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1CXXBoolLiteralExpr.html">CXXBoolLiteralExpr</a>&gt;,
            Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1FloatingLiteral.html">FloatingLiteral</a>&gt;, Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1IntegerLiteral.html">IntegerLiteral</a>&gt;
 </pre></td></tr>
@@ -2866,6 +2890,14 @@ <h2 id="narrowing-matchers">Narrowing Matchers</h2>
 integerLiteral(equals(42))
   matches 42
 
+Note that you cannot directly match a negative numeric literal because the
+minus sign is not part of the literal: It is a unary operator whose operand
+is the positive numeric literal. Instead, you must use a unaryOperator()
+matcher to match the minus sign:
+
+unaryOperator(hasOperatorName("-"),
+              hasUnaryOperand(integerLiteral(equals(13))))
+
 Usable as: Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1CharacterLiteral.html">CharacterLiteral</a>&gt;, Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1CXXBoolLiteralExpr.html">CXXBoolLiteralExpr</a>&gt;,
            Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1FloatingLiteral.html">FloatingLiteral</a>&gt;, Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1IntegerLiteral.html">IntegerLiteral</a>&gt;
 </pre></td></tr>

include/clang/ASTMatchers/ASTMatchers.h

@@ -3821,6 +3821,14 @@ AST_MATCHER_P(CompoundStmt, statementCountIs, unsigned, N) {
 /// integerLiteral(equals(42))
 ///   matches 42
 ///
+/// Note that you cannot directly match a negative numeric literal because the
+/// minus sign is not part of the literal: It is a unary operator whose operand
+/// is the positive numeric literal. Instead, you must use a unaryOperator()
+/// matcher to match the minus sign:
+///
+/// unaryOperator(hasOperatorName("-"),
+///               hasUnaryOperand(integerLiteral(equals(13))))
+///
 /// Usable as: Matcher<CharacterLiteral>, Matcher<CXXBoolLiteralExpr>,
 ///            Matcher<FloatingLiteral>, Matcher<IntegerLiteral>
 template <typename ValueT>

unittests/ASTMatchers/ASTMatchersNodeTest.cpp

@@ -666,6 +666,12 @@ TEST(Matcher, IntegerLiterals) {
   EXPECT_TRUE(notMatches("int i = 'a';", HasIntLiteral));
   EXPECT_TRUE(notMatches("int i = 1e10;", HasIntLiteral));
   EXPECT_TRUE(notMatches("int i = 10.0;", HasIntLiteral));
+
+  // Negative integers.
+  EXPECT_TRUE(
+      matches("int i = -10;",
+              unaryOperator(hasOperatorName("-"),
+                            hasUnaryOperand(integerLiteral(equals(10))))));
 }
 
 TEST(Matcher, FloatLiterals) {