From b7ee7e01867e3e4f6f5e247ce02c783f4cb93833 Mon Sep 17 00:00:00 2001
From: danakj <danakj@chromium.org>
Date: Thu, 14 Sep 2023 15:22:02 -0400
Subject: [PATCH] Handle namespaces in parsing types, as seen in std::enable_if

Big TODO in the test for better things to do with enable_if still.
---
 subdoc/lib/type.cc            | 18 ++++++----
 subdoc/tests/type_unittest.cc | 62 +++++++++++++++++++++++++++++++++--
 2 files changed, 70 insertions(+), 10 deletions(-)

diff --git a/subdoc/lib/type.cc b/subdoc/lib/type.cc
index 4226dde18..e44a769d9 100644
--- a/subdoc/lib/type.cc
+++ b/subdoc/lib/type.cc
@@ -241,19 +241,23 @@ Type build_local_type_internal(
         nested_names.push(
             TypeOrValue(TypeOrValueChoice::with<TypeOrValueTag::Value>(
                 std::string(spec->getAsIdentifier()->getName()))));
-      } else {
-        if (kind != clang::NestedNameSpecifier::TypeSpec &&
-            kind != clang::NestedNameSpecifier::TypeSpecWithTemplate) {
-          qualtype->dump();
-          loc.dump(sm);
-          sus::unreachable();
-        }
+      } else if (kind == clang::NestedNameSpecifier::Namespace ||
+                 kind == clang::NestedNameSpecifier::NamespaceAlias) {
+        // Namespaces are consumed/used as part of the type that comes after
+        // them.
+      } else if (kind == clang::NestedNameSpecifier::TypeSpec ||
+                 kind == clang::NestedNameSpecifier::TypeSpecWithTemplate) {
         nested_names.push(
             TypeOrValue(TypeOrValueChoice::with<TypeOrValueTag::Type>(
                 build_local_type_internal(
                     clang::QualType(spec->getAsType(), 0u),
                     llvm::ArrayRef<clang::NamedDecl*>(), sm, preprocessor,
                     loc))));
+      } else {
+        qualtype->dump();
+        loc.dump(sm);
+        fmt::println(stderr, "\nkind: {}", (int)kind);
+        sus::unreachable();
       }
       spec = spec->getPrefix();
     }
diff --git a/subdoc/tests/type_unittest.cc b/subdoc/tests/type_unittest.cc
index 682fae96f..1bbfd8bbd 100644
--- a/subdoc/tests/type_unittest.cc
+++ b/subdoc/tests/type_unittest.cc
@@ -1848,10 +1848,10 @@ TEST_F(SubDocTypeTest, VariadicConcept) {
 
 TEST_F(SubDocTypeTest, DependentNameType) {
   const char test[] = R"(
-    template <class T> struct R { using RType = T; };
-    template <class T> struct S { using SType = T; };
+    namespace a { template <class T> struct R { using RType = T; }; }
+    namespace b { template <class T> struct S { using SType = T; }; }
     template <class T>
-    void f(typename R<S<T>>::RType::SType&);
+    void f(typename a::R<b::S<T>>::RType::SType&);
   )";
   run_test(test, [](clang::ASTContext& cx, clang::Preprocessor& preprocessor) {
     auto [qual, loc] = find_function_parm("f", cx).unwrap();
@@ -1865,6 +1865,12 @@ TEST_F(SubDocTypeTest, DependentNameType) {
         t.nested_names[0u].choice.as<subdoc::TypeOrValueTag::Type>();
     EXPECT_EQ(n1.category, subdoc::TypeCategory::Type);
     EXPECT_EQ(n1.name, "R");
+    EXPECT_EQ(n1.namespace_path, sus::vec("a"));
+    const subdoc::Type& n1p1 =
+        n1.template_params[0u].choice.as<subdoc::TypeOrValueTag::Type>();
+    EXPECT_EQ(n1p1.category, subdoc::TypeCategory::Type);
+    EXPECT_EQ(n1p1.name, "S");
+    EXPECT_EQ(n1p1.namespace_path, sus::vec("b"));
     const std::string& n2 =
         t.nested_names[1u].choice.as<subdoc::TypeOrValueTag::Value>();
     EXPECT_EQ(n2, "RType");
@@ -2211,4 +2217,54 @@ TEST_F(SubDocTypeTest, PointerToArrayOfPointers) {
   });
 }
 
+TEST_F(SubDocTypeTest, EnableIfReturn) {
+  const char test[] = R"(
+    namespace std {
+      template<bool B, class T = void>
+      struct enable_if {};
+
+      template<class T>
+      struct enable_if<true, T> { using type = T; };
+    }
+
+    template <class... T>
+    struct C {
+      static constexpr bool value = true;
+    };
+
+    struct S {};
+    template <class T>
+    typename std::enable_if<C<T, S>::value>::type f();
+  )";
+  run_test(test, [](clang::ASTContext& cx, clang::Preprocessor& preprocessor) {
+    auto [qual, loc] = find_function_return("f", cx).unwrap();
+    subdoc::Type t = subdoc::build_local_type(qual, cx.getSourceManager(),
+                                              preprocessor, loc);
+
+    // TODO: There's things that we could do better here, by parsing the
+    // expression in the enable_if, much like we'd like to parse expressions
+    // in requires clauses.
+    // - We could pull the whole condition of enable_if<cond> out as a
+    //   constraint and show it in the requires list. So types could come with
+    //   a constraint list.
+    // - Then the return type should just be the `type` argument of the
+    //   enable_if statement, which defaults to void so is void here.
+    //
+    // Even more simply for now, without enable_if special cases, we could:
+    // - When we get to the template argument of type Expr, we could parse that
+    //   and find all the types, instead of just turning it into a string!
+    EXPECT_EQ(t.category, subdoc::TypeCategory::TemplateVariable);
+    EXPECT_EQ(t.name, "type");
+    EXPECT_EQ(t.refs, subdoc::Refs::None);
+    const subdoc::Type& t1 =
+        t.nested_names[0u].choice.as<subdoc::TypeOrValueTag::Type>();
+    EXPECT_EQ(t1.category, subdoc::TypeCategory::Type);
+    EXPECT_EQ(t1.name, "enable_if");
+    EXPECT_EQ(t1.namespace_path, sus::vec("std"));
+    EXPECT_EQ(t1.nested_names.len(), 0u);
+
+    EXPECT_EQ(make_string("foo", t), "!enable_if!<C<T, S>::value>::type foo");
+  });
+}
+
 }  // namespace