[clang] [ClangRepl] Type Directed Code Completion (PR #67349)

[Vassil Vassilev via cfe-commits]

================
@@ -56,26 +63,146 @@ class ReplCompletionConsumer : public CodeCompleteConsumer {
   std::shared_ptr<GlobalCodeCompletionAllocator> CCAllocator;
   CodeCompletionTUInfo CCTUInfo;
   std::vector<std::string> &Results;
+  ReplCodeCompleter &CC;
+};
+
+// The class CompletionContextHandler contains four interfaces, each of
+// which handles one type of completion result.
+// Its substract classes are used to create concrete handlers based on
+// CodeCompletionContext.
+class CompletionContextHandler {
+protected:
+  CodeCompletionContext CCC;
+  std::vector<std::string> &Results;
+
+private:
+  Sema &S;
+
+public:
+  CompletionContextHandler(Sema &S, CodeCompletionContext CCC,
+                           std::vector<std::string> &Results)
+      : CCC(CCC), Results(Results), S(S) {}
+
+  // converts a Declaration completion result to a completion string, and then
+  // stores it in Results.
+  virtual void handleDeclaration(const CodeCompletionResult &Result) {
+    auto PreferredType = CCC.getPreferredType();
+    if (PreferredType.isNull()) {
+      Results.push_back(Result.Declaration->getName().str());
+      return;
+    }
+
+    if (auto *VD = dyn_cast<VarDecl>(Result.Declaration)) {
+      auto ArgumentType = VD->getType();
+      if (PreferredType->isReferenceType()) {
+        QualType RT = PreferredType->castAs<ReferenceType>()->getPointeeType();
+        Sema::ReferenceConversions RefConv;
+        Sema::ReferenceCompareResult RefRelationship =
+            S.CompareReferenceRelationship(SourceLocation(), RT, ArgumentType,
+                                           &RefConv);
+        switch (RefRelationship) {
+        case Sema::Ref_Compatible:
+        case Sema::Ref_Related:
+          Results.push_back(VD->getName().str());
+          break;
+        case Sema::Ref_Incompatible:
+          break;
+        }
+      } else if (S.Context.hasSameType(ArgumentType, PreferredType)) {
+        Results.push_back(VD->getName().str());
+      }
+    }
+  }
+
+  // converts a Keyword completion result to a completion string, and then
+  // stores it in Results.
+  virtual void handleKeyword(const CodeCompletionResult &Result) {
+    auto Prefix = S.getPreprocessor().getCodeCompletionFilter();
+    // Add keyword to the completion results only if we are in a type-aware
+    // situation.
+    if (!CCC.getBaseType().isNull() || !CCC.getPreferredType().isNull())
+      return;
+    if (StringRef(Result.Keyword).startswith(Prefix))
+      Results.push_back(Result.Keyword);
+  }
+
+  // converts a Pattern completion result to a completion string, and then
+  // stores it in Results.
----------------
vgvassilev wrote:

```suggestion
  /// Converts a Pattern completion result to a completion string, and then
  /// stores it in Results.
```

https://github.com/llvm/llvm-project/pull/67349