From 44153f94e8511b60afe84e893aee52b01d74ab34 Mon Sep 17 00:00:00 2001
From: Jacob Dufault <jacobdufault@gmail.com>
Date: Sat, 20 May 2017 17:19:32 -0700
Subject: [PATCH] Fix auto variable type deduction when auto is a pointer.

---
 src/indexer.cc                            |  3 +-
 src/libclangmm/Cursor.cc                  | 16 ++++++++
 src/libclangmm/Cursor.h                   |  2 +
 tests/vars/deduce_auto_type.cc            | 48 ++++++++++++++++++++++
 tests/vars/type_instance_on_using_type.cc | 50 +++++++++++++++++++++++
 5 files changed, 117 insertions(+), 2 deletions(-)
 create mode 100644 tests/vars/deduce_auto_type.cc
 create mode 100644 tests/vars/type_instance_on_using_type.cc

diff --git a/src/indexer.cc b/src/indexer.cc
index 1e23e13a..dddb65e7 100644
--- a/src/indexer.cc
+++ b/src/indexer.cc
@@ -481,8 +481,7 @@ clang::VisiterResult VisitDeclForTypeUsageVisitor(
 // (ie, Foo<A,B> => Foo<*,*>).
 optional<IndexTypeId> ResolveToDeclarationType(IndexFile* db,
                                                clang::Cursor cursor) {
-  clang::Cursor declaration =
-      cursor.get_type().strip_qualifiers().get_declaration();
+  clang::Cursor declaration = cursor.get_declaration();
   declaration = declaration.template_specialization_to_template_definition();
   std::string usr = declaration.get_usr();
   if (usr != "")
diff --git a/src/libclangmm/Cursor.cc b/src/libclangmm/Cursor.cc
index 7af78e9e..79f2ab99 100644
--- a/src/libclangmm/Cursor.cc
+++ b/src/libclangmm/Cursor.cc
@@ -34,6 +34,10 @@ std::string Type::get_usr() const {
   return clang::Cursor(clang_getTypeDeclaration(cx_type)).get_usr();
 }
 
+Type Type::get_canonical() const {
+  return clang_getCanonicalType(cx_type);
+}
+
 Type Type::strip_qualifiers() const {
   // CXRefQualifierKind qualifiers = clang_Type_getCXXRefQualifier(cx_type)
   switch (cx_type.kind) {
@@ -112,6 +116,18 @@ CXCursorKind Cursor::get_kind() const {
   return cx_cursor.kind;
 }
 
+Cursor Cursor::get_declaration() const {
+  Type type = get_type();
+  
+  // auto x = new Foo() will not be deduced to |Foo| if we do not use the
+  // canonical type. However, a canonical type will look past typedefs so we
+  // will not accurately report variables on typedefs if we always do this.
+  if (type.cx_type.kind == CXType_Auto)
+    type = type.get_canonical();
+
+  return type.strip_qualifiers().get_declaration();
+}
+
 Type Cursor::get_type() const {
   return Type(clang_getCursorType(cx_cursor));
 }
diff --git a/src/libclangmm/Cursor.h b/src/libclangmm/Cursor.h
index e504280a..de27bcd1 100644
--- a/src/libclangmm/Cursor.h
+++ b/src/libclangmm/Cursor.h
@@ -23,6 +23,7 @@ class Type {
   CXCursor get_declaration() const;
   std::string get_usr() const;
   std::string get_spelling() const;
+  Type get_canonical() const;
 
   // Try to resolve this type and remove qualifies, ie, Foo* will become Foo
   Type strip_qualifiers() const;
@@ -46,6 +47,7 @@ class Cursor {
   bool operator!=(const Cursor& rhs) const;
 
   CXCursorKind get_kind() const;
+  Cursor get_declaration() const;
   Type get_type() const;
   std::string get_spelling() const;
   std::string get_display_name() const;
diff --git a/tests/vars/deduce_auto_type.cc b/tests/vars/deduce_auto_type.cc
new file mode 100644
index 00000000..f6df559c
--- /dev/null
+++ b/tests/vars/deduce_auto_type.cc
@@ -0,0 +1,48 @@
+class Foo {};
+void f() {
+  auto x = new Foo();
+  auto* y = new Foo();
+}
+
+/*
+OUTPUT:
+{
+  "types": [{
+      "id": 0,
+      "usr": "c:@S@Foo",
+      "short_name": "Foo",
+      "detailed_name": "Foo",
+      "definition_spelling": "1:7-1:10",
+      "definition_extent": "1:1-1:13",
+      "instances": [0, 1],
+      "uses": ["1:7-1:10", "3:16-3:19", "4:17-4:20"]
+    }],
+  "funcs": [{
+      "id": 0,
+      "usr": "c:@F@f#",
+      "short_name": "f",
+      "detailed_name": "void f()",
+      "definition_spelling": "2:6-2:7",
+      "definition_extent": "2:1-5:2"
+    }],
+  "vars": [{
+      "id": 0,
+      "usr": "c:deduce_auto_type.cc@29@F@f#@x",
+      "short_name": "x",
+      "detailed_name": "Foo * x",
+      "definition_spelling": "3:8-3:9",
+      "definition_extent": "3:3-3:21",
+      "variable_type": 0,
+      "uses": ["3:8-3:9"]
+    }, {
+      "id": 1,
+      "usr": "c:deduce_auto_type.cc@52@F@f#@y",
+      "short_name": "y",
+      "detailed_name": "Foo * y",
+      "definition_spelling": "4:9-4:10",
+      "definition_extent": "4:3-4:22",
+      "variable_type": 0,
+      "uses": ["4:9-4:10"]
+    }]
+}
+*/
diff --git a/tests/vars/type_instance_on_using_type.cc b/tests/vars/type_instance_on_using_type.cc
new file mode 100644
index 00000000..3f87c118
--- /dev/null
+++ b/tests/vars/type_instance_on_using_type.cc
@@ -0,0 +1,50 @@
+struct S {};
+using F = S;
+void Foo() {
+  F a;
+}
+
+// TODO: Should we also add a usage to |S|?
+
+/*
+OUTPUT:
+{
+  "types": [{
+      "id": 0,
+      "usr": "c:@S@S",
+      "short_name": "S",
+      "detailed_name": "S",
+      "definition_spelling": "1:8-1:9",
+      "definition_extent": "1:1-1:12",
+      "uses": ["1:8-1:9", "2:11-2:12"]
+    }, {
+      "id": 1,
+      "usr": "c:@F",
+      "short_name": "F",
+      "detailed_name": "F",
+      "definition_spelling": "2:7-2:8",
+      "definition_extent": "2:1-2:12",
+      "alias_of": 0,
+      "instances": [0],
+      "uses": ["2:7-2:8", "4:3-4:4"]
+    }],
+  "funcs": [{
+      "id": 0,
+      "usr": "c:@F@Foo#",
+      "short_name": "Foo",
+      "detailed_name": "void Foo()",
+      "definition_spelling": "3:6-3:9",
+      "definition_extent": "3:1-5:2"
+    }],
+  "vars": [{
+      "id": 0,
+      "usr": "c:type_instance_on_using_type.cc@44@F@Foo#@a",
+      "short_name": "a",
+      "detailed_name": "F a",
+      "definition_spelling": "4:5-4:6",
+      "definition_extent": "4:3-4:6",
+      "variable_type": 1,
+      "uses": ["4:5-4:6"]
+    }]
+}
+*/