[ASTMatchers] add three matchers for dependent expressions

Summary:
The new matchers can be used to check if an expression is type-, value- or instantiation-dependent
in a templated context.
These matchers are used in a clang-tidy check and generally useful as the
problem of unresolved templates occurs more often in clang-tidy and they
provide an easy way to check for this issue.

Reviewers: aaron.ballman, alexfh, klimek

Reviewed By: aaron.ballman

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D51880

llvm-svn: 341958

clang/docs/LibASTMatchersReference.html

@@ -2758,6 +2758,46 @@ enum class Y {};
 </pre></td></tr>
 
 
+<tr><td>Matcher&lt;<a href="http://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
+sizeof is known.
+  template&lt;typename T&gt;
+  void f(T x, T y) { sizeof(sizeof(T() + T()); }
+expr(isInstantiationDependent()) matches sizeof(sizeof(T() + T())
+</pre></td></tr>
+
+
+<tr><td>Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1Expr.html">Expr</a>&gt;</td><td class="name" onclick="toggle('isTypeDependent0')"><a name="isTypeDependent0Anchor">isTypeDependent</a></td><td></td></tr>
+<tr><td colspan="4" class="doc" id="isTypeDependent0"><pre>Matches expressions that are type-dependent because the template type
+is not yet instantiated.
+
+For example, the expressions "x" and "x + y" are type-dependent in
+the following code, but "y" is not type-dependent:
+  template&lt;typename T&gt;
+  void add(T x, int y) {
+    x + y;
+  }
+expr(isTypeDependent()) matches x + y
+</pre></td></tr>
+
+
+<tr><td>Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1Expr.html">Expr</a>&gt;</td><td class="name" onclick="toggle('isValueDependent0')"><a name="isValueDependent0Anchor">isValueDependent</a></td><td></td></tr>
+<tr><td colspan="4" class="doc" id="isValueDependent0"><pre>Matches expression that are value-dependent because they contain a
+non-type template parameter.
+
+For example, the array bound of "Chars" in the following example is
+value-dependent.
+  template&lt;int Size&gt; int f() { return Size; }
+expr(isValueDependent()) matches return Size
+</pre></td></tr>
+
+
 <tr><td>Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1FieldDecl.html">FieldDecl</a>&gt;</td><td class="name" onclick="toggle('hasBitWidth0')"><a name="hasBitWidth0Anchor">hasBitWidth</a></td><td>unsigned Width</td></tr>
 <tr><td colspan="4" class="doc" id="hasBitWidth0"><pre>Matches non-static data members that are bit-fields of the specified
 bit width.

clang/include/clang/ASTMatchers/ASTMatchers.h

@@ -816,6 +816,48 @@ AST_MATCHER_P(QualType, ignoringParens,
   return InnerMatcher.matches(Node.IgnoreParens(), Finder, Builder);
 }
 
+/// 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
+/// sizeof is known.
+/// \code
+///   template<typename T>
+///   void f(T x, T y) { sizeof(sizeof(T() + T()); }
+/// \endcode
+/// expr(isInstantiationDependent()) matches sizeof(sizeof(T() + T())
+AST_MATCHER(Expr, isInstantiationDependent) {
+  return Node.isInstantiationDependent();
+}
+
+/// Matches expressions that are type-dependent because the template type
+/// is not yet instantiated.
+///
+/// For example, the expressions "x" and "x + y" are type-dependent in
+/// the following code, but "y" is not type-dependent:
+/// \code
+///   template<typename T>
+///   void add(T x, int y) {
+///     x + y;
+///   }
+/// \endcode
+/// expr(isTypeDependent()) matches x + y
+AST_MATCHER(Expr, isTypeDependent) { return Node.isTypeDependent(); }
+
+/// Matches expression that are value-dependent because they contain a
+/// non-type template parameter.
+///
+/// For example, the array bound of "Chars" in the following example is
+/// value-dependent.
+/// \code
+///   template<int Size> int f() { return Size; }
+/// \endcode
+/// expr(isValueDependent()) matches return Size
+AST_MATCHER(Expr, isValueDependent) { return Node.isValueDependent(); }
+
 /// Matches classTemplateSpecializations, templateSpecializationType and
 /// functionDecl where the n'th TemplateArgument matches the given InnerMatcher.
 ///

clang/lib/ASTMatchers/Dynamic/Registry.cpp

@@ -357,6 +357,7 @@ RegistryMaps::RegistryMaps() {
   REGISTER_MATCHER(isExpansionInSystemHeader);
   REGISTER_MATCHER(isInteger);
   REGISTER_MATCHER(isIntegral);
+  REGISTER_MATCHER(isInstantiationDependent);
   REGISTER_MATCHER(isInTemplateInstantiation);
   REGISTER_MATCHER(isLambda);
   REGISTER_MATCHER(isListInitialization);
@@ -376,8 +377,10 @@ RegistryMaps::RegistryMaps() {
   REGISTER_MATCHER(isStaticStorageClass);
   REGISTER_MATCHER(isStruct);
   REGISTER_MATCHER(isTemplateInstantiation);
+  REGISTER_MATCHER(isTypeDependent);
   REGISTER_MATCHER(isUnion);
   REGISTER_MATCHER(isUnsignedInteger);
+  REGISTER_MATCHER(isValueDependent);
   REGISTER_MATCHER(isVariadic);
   REGISTER_MATCHER(isVirtual);
   REGISTER_MATCHER(isVirtualAsWritten);

clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp

@@ -1768,6 +1768,48 @@ TEST(IsInTemplateInstantiation, Sharing) {
     Matcher));
 }
 
+TEST(IsInstantiationDependent, MatchesNonValueTypeDependent) {
+  EXPECT_TRUE(matches(
+      "template<typename T> void f() { (void) sizeof(sizeof(T() + T())); }",
+      expr(isInstantiationDependent())));
+}
+
+TEST(IsInstantiationDependent, MatchesValueDependent) {
+  EXPECT_TRUE(matches("template<int T> int f() { return T; }",
+                      expr(isInstantiationDependent())));
+}
+
+TEST(IsInstantiationDependent, MatchesTypeDependent) {
+  EXPECT_TRUE(matches("template<typename T> T f() { return T(); }",
+                      expr(isInstantiationDependent())));
+}
+
+TEST(IsTypeDependent, MatchesTypeDependent) {
+  EXPECT_TRUE(matches("template<typename T> T f() { return T(); }",
+                      expr(isTypeDependent())));
+}
+
+TEST(IsTypeDependent, NotMatchesValueDependent) {
+  EXPECT_TRUE(notMatches("template<int T> int f() { return T; }",
+                         expr(isTypeDependent())));
+}
+
+TEST(IsValueDependent, MatchesValueDependent) {
+  EXPECT_TRUE(matches("template<int T> int f() { return T; }",
+                      expr(isValueDependent())));
+}
+
+TEST(IsValueDependent, MatchesTypeDependent) {
+  EXPECT_TRUE(matches("template<typename T> T f() { return T(); }",
+                      expr(isValueDependent())));
+}
+
+TEST(IsValueDependent, MatchesInstantiationDependent) {
+  EXPECT_TRUE(matches(
+      "template<typename T> void f() { (void) sizeof(sizeof(T() + T())); }",
+      expr(isValueDependent())));
+}
+
 TEST(IsExplicitTemplateSpecialization,
      DoesNotMatchPrimaryTemplate) {
   EXPECT_TRUE(notMatches(