[CodeComplete] Member completion for concept-constrained types.

Summary:
The basic idea is to walk through the concept definition, looking for
t.foo() where t has the constrained type.

In this patch:
 - nested types are recognized and offered after ::
 - variable/function members are recognized and offered after the correct
   dot/arrow/colon trigger
 - member functions are recognized (anything directly called). parameter
   types are presumed to be the argument types. parameters are unnamed.
 - result types are available when a requirement has a type constraint.
   These are printed as constraints, except same_as<T> which prints as T.

Not in this patch:
 - support for merging/overloading when two locations describe the same member.
   The last one wins, for any given name. This is probably important...
 - support for nested template members (T::x<int>)
 - support for completing members of (instantiations of) template template parameters

Reviewers: nridge, saar.raz

Subscribers: mgrang, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D73649

Author: sam-mccall

clang/include/clang/Sema/Scope.h

@@ -320,9 +320,7 @@ class Scope {
 
   /// isDeclScope - Return true if this is the scope that the specified decl is
   /// declared in.
-  bool isDeclScope(Decl *D) {
-    return DeclsInScope.count(D) != 0;
-  }
+  bool isDeclScope(const Decl *D) const { return DeclsInScope.count(D) != 0; }
 
   DeclContext *getEntity() const { return Entity; }
   void setEntity(DeclContext *E) { Entity = E; }

clang/lib/Sema/CodeCompleteConsumer.cpp

@@ -570,29 +570,10 @@ void PrintingCodeCompleteConsumer::ProcessCodeCompleteResults(
         if (const char *BriefComment = CCS->getBriefComment())
           OS << " : " << BriefComment;
       }
-      for (const FixItHint &FixIt : Results[I].FixIts) {
-        const SourceLocation BLoc = FixIt.RemoveRange.getBegin();
-        const SourceLocation ELoc = FixIt.RemoveRange.getEnd();
-
-        SourceManager &SM = SemaRef.SourceMgr;
-        std::pair<FileID, unsigned> BInfo = SM.getDecomposedLoc(BLoc);
-        std::pair<FileID, unsigned> EInfo = SM.getDecomposedLoc(ELoc);
-        // Adjust for token ranges.
-        if (FixIt.RemoveRange.isTokenRange())
-          EInfo.second += Lexer::MeasureTokenLength(ELoc, SM, SemaRef.LangOpts);
-
-        OS << " (requires fix-it:"
-           << " {" << SM.getLineNumber(BInfo.first, BInfo.second) << ':'
-           << SM.getColumnNumber(BInfo.first, BInfo.second) << '-'
-           << SM.getLineNumber(EInfo.first, EInfo.second) << ':'
-           << SM.getColumnNumber(EInfo.first, EInfo.second) << "}"
-           << " to \"" << FixIt.CodeToInsert << "\")";
-      }
-      OS << '\n';
       break;
 
     case CodeCompletionResult::RK_Keyword:
-      OS << Results[I].Keyword << '\n';
+      OS << Results[I].Keyword;
       break;
 
     case CodeCompletionResult::RK_Macro:
@@ -602,13 +583,31 @@ void PrintingCodeCompleteConsumer::ProcessCodeCompleteResults(
               includeBriefComments())) {
         OS << " : " << CCS->getAsString();
       }
-      OS << '\n';
       break;
 
     case CodeCompletionResult::RK_Pattern:
-      OS << "Pattern : " << Results[I].Pattern->getAsString() << '\n';
+      OS << "Pattern : " << Results[I].Pattern->getAsString();
       break;
     }
+    for (const FixItHint &FixIt : Results[I].FixIts) {
+      const SourceLocation BLoc = FixIt.RemoveRange.getBegin();
+      const SourceLocation ELoc = FixIt.RemoveRange.getEnd();
+
+      SourceManager &SM = SemaRef.SourceMgr;
+      std::pair<FileID, unsigned> BInfo = SM.getDecomposedLoc(BLoc);
+      std::pair<FileID, unsigned> EInfo = SM.getDecomposedLoc(ELoc);
+      // Adjust for token ranges.
+      if (FixIt.RemoveRange.isTokenRange())
+        EInfo.second += Lexer::MeasureTokenLength(ELoc, SM, SemaRef.LangOpts);
+
+      OS << " (requires fix-it:"
+         << " {" << SM.getLineNumber(BInfo.first, BInfo.second) << ':'
+         << SM.getColumnNumber(BInfo.first, BInfo.second) << '-'
+         << SM.getLineNumber(EInfo.first, EInfo.second) << ':'
+         << SM.getColumnNumber(EInfo.first, EInfo.second) << "}"
+         << " to \"" << FixIt.CodeToInsert << "\")";
+    }
+    OS << '\n';
   }
 }