From 74177a559e16c5c260d8934a7f5a7a959e4565b3 Mon Sep 17 00:00:00 2001
From: Christian Kandeler <christian.kandeler@qt.io>
Date: Mon, 15 Feb 2021 12:27:23 +0100
Subject: [PATCH] clangbackend: Work around libclang cursor bug

... involving accessing the member of a nested anonymous union from
within the surrounding class. libclang reports a CXCursor_CXXThisExpr
for this location instead of a CXCursor_MemberRefExpr. However, the
latter is still locatable in the AST, so we can correct this.

Fixes: QTCREATORBUG-25342
Change-Id: I1eba13d5153205a52b3689d8ad52493a56b76c07
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
---
 src/tools/clangbackend/source/clangfollowsymbol.cpp | 10 ++++++++++
 tests/unit/unittest/clangfollowsymbol-test.cpp      |  7 +++++++
 tests/unit/unittest/data/followsymbol_main.cpp      | 13 +++++++++++++
 3 files changed, 30 insertions(+)

diff --git a/src/tools/clangbackend/source/clangfollowsymbol.cpp b/src/tools/clangbackend/source/clangfollowsymbol.cpp
index e2c619ef3fc..81aaeec5c89 100644
--- a/src/tools/clangbackend/source/clangfollowsymbol.cpp
+++ b/src/tools/clangbackend/source/clangfollowsymbol.cpp
@@ -95,6 +95,16 @@ FollowSymbolResult FollowSymbol::followSymbol(CXTranslationUnit tu,
         return SourceRangeContainer();
 
     Cursor cursor{cursors[tokenIndex]};
+    if (cursor.kind() == CXCursor_CXXThisExpr && tokenSpelling != "this") { // QTCREATORBUG-25342
+        cursor.semanticParent().visit([&cursor](CXCursor current, CXCursor parent) {
+            if (current == cursor && parent.kind == CXCursor_MemberRefExpr
+                    && cursor.sourceLocation() == Cursor(parent).sourceLocation()) {
+                cursor = parent;
+                return CXChildVisit_Break;
+            }
+            return CXChildVisit_Recurse;
+        });
+    }
 
     if (cursor.kind() == CXCursor_InclusionDirective) {
         CXFile file = clang_getIncludedFile(cursors[tokenIndex].cx());
diff --git a/tests/unit/unittest/clangfollowsymbol-test.cpp b/tests/unit/unittest/clangfollowsymbol-test.cpp
index e836cc83c66..29c0a702b37 100644
--- a/tests/unit/unittest/clangfollowsymbol-test.cpp
+++ b/tests/unit/unittest/clangfollowsymbol-test.cpp
@@ -209,6 +209,13 @@ TEST_F(FollowSymbol, CursorOnMemberReference)
     ASSERT_THAT(memberDeclaration, MatchesHeaderSourceRange(38, 18, 6));
 }
 
+TEST_F(FollowSymbol, CursorOnMemberReferenceAnonymousUnion)
+{
+    const auto memberDeclaration = followSymbol(91, 20);
+
+    ASSERT_THAT(memberDeclaration, MatchesSourceRange(86, 13, 1));
+}
+
 TEST_F(FollowSymbol, CursorOnMemberDeclaration)
 {
     const auto sameMemberDeclaration = followHeaderSymbol(38, 18);
diff --git a/tests/unit/unittest/data/followsymbol_main.cpp b/tests/unit/unittest/data/followsymbol_main.cpp
index 9b16158e40d..f967d8653be 100644
--- a/tests/unit/unittest/data/followsymbol_main.cpp
+++ b/tests/unit/unittest/data/followsymbol_main.cpp
@@ -80,3 +80,16 @@ int Bar::operator&() {
 Bar& Bar::operator[](int) {
     return *this;
 }
+
+struct S {
+    union  {
+        int i = 12;
+        void *something;
+    };
+    int func(bool b) {
+        if (b)
+            return i;
+        int i = 42;
+        return i;
+    }
+};