[backported/clang-7][libclang] Optionally add code completion results for arrow instead of dot

--------------------------------------------------------------------------
* https://reviews.llvm.org/D46862
--------------------------------------------------------------------------

Follow up for https://reviews.llvm.org/D41537 -
libclang part is extracted into this review

Change-Id: Ib166eb7b8675be605c81330df0c5f342942815ce
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>

3 files changed, 124 insertions, 25 deletions

diff --git a/include/clang-c/Index.h b/include/clang-c/Index.h
index d06c82a4db..41534f68e6 100644
--- a/include/clang-c/Index.h
+++ b/include/clang-c/Index.h
@@ -36,6 +36,7 @@
 #define CINDEX_VERSION_HAS_ISINVALIDECL_BACKPORTED
 #define CINDEX_VERSION_HAS_PRETTYDECL_BACKPORTED
 #define CINDEX_VERSION_HAS_LIMITSKIPFUNCTIONBODIESTOPREAMBLE_BACKPORTED
+#define CINDEX_VERSION_HAS_COMPLETION_FIXITS_BACKPORTED
 
 #define CINDEX_VERSION_ENCODE(major, minor) ( \
       ((major) * 10000)                       \
@@ -4738,6 +4739,20 @@ typedef struct {
 } CXToken;
 
 /**
+ * \brief Get the raw lexical token starting with the given location.
+ *
+ * \param TU the translation unit whose text is being tokenized.
+ *
+ * \param Location the source location with which the token starts.
+ *
+ * \returns The token starting with the given location or NULL if no such tokens
+ * exist. The returned pointer must be freed with clang_disposeTokens before the
+ * translation unit is destroyed.
+ */
+CINDEX_LINKAGE CXToken *clang_getToken(CXTranslationUnit TU,
+                                       CXSourceLocation Location);
+
+/**
  * \brief Determine the kind of the given token.
  */
 CINDEX_LINKAGE CXTokenKind clang_getTokenKind(CXToken);
@@ -5233,6 +5248,70 @@ typedef struct {
 } CXCodeCompleteResults;
 
 /**
+ * \brief Retrieve the number of fix-its for the given completion string.
+ *
+ * Calling this makes sense only if CXCodeComplete_IncludeCompletionsWithFixIts
+ * option was set.
+ *
+ * \param results The structure keeping all completion results
+ *
+ * \param completion_index The index of the completion
+ *
+ * \return The number of fix-its which must be applied before the completion at
+ * completion_index can be applied
+ */
+CINDEX_LINKAGE unsigned
+clang_getCompletionNumFixIts(CXCodeCompleteResults *results,
+                             unsigned completion_index);
+
+/**
+ * \brief Fix-its that *must* be applied before inserting the text for the
+ * corresponding completion.
+ *
+ * By default, clang_codeCompleteAt() only returns completions with empty
+ * fix-its. Extra completions with non-empty fix-its should be explicitly
+ * requested by setting CXCodeComplete_IncludeCompletionsWithFixIts.
+ *
+ * For the clients to be able to compute position of the cursor after applying
+ * fix-its, the following conditions are guaranteed to hold for
+ * replacement_range of the stored fix-its:
+ *  - Ranges in the fix-its are guaranteed to never contain the completion
+ *  point (or identifier under completion point, if any) inside them, except
+ *  at the start or at the end of the range.
+ *  - If a fix-it range starts or ends with completion point (or starts or
+ *  ends after the identifier under completion point), it will contain at
+ *  least one character. It allows to unambiguously recompute completion
+ *  point after applying the fix-it.
+ *
+ * The intuition is that provided fix-its change code around the identifier we
+ * complete, but are not allowed to touch the identifier itself or the
+ * completion point. One example of completions with corrections are the ones
+ * replacing '.' with '->' and vice versa:
+ *
+ * std::unique_ptr<std::vector<int>> vec_ptr;
+ * In 'vec_ptr.^', one of the completions is 'push_back', it requires
+ * replacing '.' with '->'.
+ * In 'vec_ptr->^', one of the completions is 'release', it requires
+ * replacing '->' with '.'.
+ *
+ * \param results The structure keeping all completion results
+ *
+ * \param completion_index The index of the completion
+ *
+ * \param fixit_index The index of the fix-it for the completion at
+ * completion_index
+ *
+ * \param replacement_range The fix-it range that must be replaced before the
+ * completion at completion_index can be applied
+ *
+ * \returns The fix-it string that must replace the code at replacement_range
+ * before the completion at completion_index can be applied
+ */
+CINDEX_LINKAGE CXString clang_getCompletionFixIt(
+    CXCodeCompleteResults *results, unsigned completion_index,
+    unsigned fixit_index, CXSourceRange *replacement_range);
+
+/**
  * \brief Flags that can be passed to \c clang_codeCompleteAt() to
  * modify its behavior.
  *
@@ -5256,7 +5335,13 @@ enum CXCodeComplete_Flags {
    * \brief Whether to include brief documentation within the set of code
    * completions returned.
    */
-  CXCodeComplete_IncludeBriefComments = 0x04
+  CXCodeComplete_IncludeBriefComments = 0x04,
+
+  /**
+   * \brief Whether to include completions with small
+   * fix-its, e.g. change '.' to '->' on member access, etc.
+   */
+  CXCodeComplete_IncludeCompletionsWithFixIts = 0x10
 };
 
 /**
diff --git a/include/clang/Basic/SourceManager.h b/include/clang/Basic/SourceManager.h
index 397ad2e77f..80e277384c 100644
--- a/include/clang/Basic/SourceManager.h
+++ b/include/clang/Basic/SourceManager.h
@@ -1137,6 +1137,18 @@ public:
   /// be used by clients.
   SourceLocation getImmediateSpellingLoc(SourceLocation Loc) const;
 
+  /// Form a SourceLocation from a FileID and Offset pair.
+  SourceLocation getComposedLoc(FileID FID, unsigned Offset) const {
+    bool Invalid = false;
+    const SrcMgr::SLocEntry &Entry = getSLocEntry(FID, &Invalid);
+    if (Invalid)
+      return SourceLocation();
+
+    unsigned GlobalOffset = Entry.getOffset() + Offset;
+    return Entry.isFile() ? SourceLocation::getFileLoc(GlobalOffset)
+                          : SourceLocation::getMacroLoc(GlobalOffset);
+  }
+
   /// \brief Decompose the specified location into a raw FileID + Offset pair.
   ///
   /// The first element is the FileID, the second is the offset from the
diff --git a/include/clang/Sema/CodeCompleteConsumer.h b/include/clang/Sema/CodeCompleteConsumer.h
index 720a150f51..002f93ade2 100644
--- a/include/clang/Sema/CodeCompleteConsumer.h
+++ b/include/clang/Sema/CodeCompleteConsumer.h
@@ -680,30 +680,33 @@ public:
   /// \brief The availability of this result.
   CXAvailabilityKind Availability;
 
-  /// \brief FixIts that *must* be applied before inserting the text for the
-  /// corresponding completion item.
+  ///\brief Fix-its that *must* be applied before inserting the text for the
+  /// corresponding completion.
   ///
-  /// Completion items with non-empty fixits will not be returned by default,
-  /// they should be explicitly requested by setting
-  /// CompletionOptions::IncludeFixIts. For the editors to be able to
-  /// compute position of the cursor for the completion item itself, the
-  /// following conditions are guaranteed to hold for RemoveRange of the stored
-  /// fixits:
-  ///  - Ranges in the fixits are guaranteed to never contain the completion
+  /// By default, CodeCompletionBuilder only returns completions with empty
+  /// fix-its. Extra completions with non-empty fix-its should be explicitly
+  /// requested by setting CompletionOptions::IncludeFixIts.
+  ///
+  /// For the clients to be able to compute position of the cursor after
+  /// applying fix-its, the following conditions are guaranteed to hold for
+  /// RemoveRange of the stored fix-its:
+  ///  - Ranges in the fix-its are guaranteed to never contain the completion
   ///  point (or identifier under completion point, if any) inside them, except
   ///  at the start or at the end of the range.
-  ///  - If a fixit range starts or ends with completion point (or starts or
+  ///  - If a fix-it range starts or ends with completion point (or starts or
   ///  ends after the identifier under completion point), it will contain at
   ///  least one character. It allows to unambiguously recompute completion
-  ///  point after applying the fixit.
-  /// The intuition is that provided fixits change code around the identifier we
-  /// complete, but are not allowed to touch the identifier itself or the
-  /// completion point. One example of completion items with corrections are the
-  /// ones replacing '.' with '->' and vice versa:
+  ///  point after applying the fix-it.
+  ///
+  /// The intuition is that provided fix-its change code around the identifier
+  /// we complete, but are not allowed to touch the identifier itself or the
+  /// completion point. One example of completions with corrections are the ones
+  /// replacing '.' with '->' and vice versa:
+  ///
   /// std::unique_ptr<std::vector<int>> vec_ptr;
-  /// In 'vec_ptr.^', one of completion items is 'push_back', it requires
+  /// In 'vec_ptr.^', one of the completions is 'push_back', it requires
   /// replacing '.' with '->'.
-  /// In 'vec_ptr->^', one of completion items is 'release', it requires
+  /// In 'vec_ptr->^', one of the completions is 'release', it requires
   /// replacing '->' with '.'.
   std::vector<FixItHint> FixIts;
 
@@ -736,13 +739,12 @@ public:
                        bool QualifierIsInformative = false,
                        bool Accessible = true,
                        std::vector<FixItHint> FixIts = std::vector<FixItHint>())
-    : Declaration(Declaration), Priority(Priority),
-      StartParameter(0), Kind(RK_Declaration),
-      Availability(CXAvailability_Available), Hidden(false),
-      QualifierIsInformative(QualifierIsInformative),
-      StartsNestedNameSpecifier(false), AllParametersAreInformative(false),
-      DeclaringEntity(false), Qualifier(Qualifier),
-      FixIts(std::move(FixIts)) {
+      : Declaration(Declaration), Priority(Priority), StartParameter(0),
+        Kind(RK_Declaration), Availability(CXAvailability_Available),
+        FixIts(std::move(FixIts)), Hidden(false),
+        QualifierIsInformative(QualifierIsInformative),
+        StartsNestedNameSpecifier(false), AllParametersAreInformative(false),
+        DeclaringEntity(false), Qualifier(Qualifier) {
     //FIXME: Add assert to check FixIts range requirements.
     computeCursorKindAndAvailability(Accessible);
   }