[CSDiag] Remove CalleeCandidateInfo::diagnoseSimpleErrors, which is

dead code now.

Author: hborla

docs/TypeChecker.rst

@@ -986,5 +986,3 @@ The things in the queue yet to be ported are:
   - Missing explicit ``Self.`` and ``self.``
   - Logic related to overload candidate ranking (``CalleeCandidateInfo``)
   - ``diagnoseParameterErrors``
-  - ``diagnoseSimpleErrors``
-

lib/Sema/CSDiag.cpp

@@ -1403,10 +1403,6 @@ bool FailureDiagnosis::visitApplyExpr(ApplyExpr *callExpr) {
                               argLabels))
     return true;
 
-  // Diagnose some simple and common errors.
-  if (calleeInfo.diagnoseSimpleErrors(callExpr))
-    return true;
-
   // Force recheck of the arg expression because we allowed unresolved types
   // before, and that turned out not to help, and now we want any diagnoses
   // from disallowing them.

lib/Sema/CalleeCandidateInfo.cpp

@@ -945,41 +945,3 @@ suggestPotentialOverloads(SourceLoc loc, bool isResult) {
                 suggestionText);
   }
 }
-
-/// Emit a diagnostic and return true if this is an error condition we can
-/// handle uniformly.  This should be called after filtering the candidate
-/// list.
-bool CalleeCandidateInfo::diagnoseSimpleErrors(const Expr *E) {
-  SourceLoc loc = E->getLoc();
-  
-  // Handle symbols marked as explicitly unavailable.
-  if (closeness == CC_Unavailable) {
-    auto decl = candidates[0].getDecl();
-    assert(decl && "Only decl-based candidates may be marked unavailable");
-    return diagnoseExplicitUnavailability(decl, loc, CS.DC,
-                                          dyn_cast<CallExpr>(E));
-  }
-  
-  // Handle symbols that are matches, but are not accessible from the current
-  // scope.
-  if (closeness == CC_Inaccessible) {
-    auto decl = candidates[0].getDecl();
-    assert(decl && "Only decl-based candidates may be marked inaccessible");
-
-    InaccessibleMemberFailure failure(
-        CS, decl, CS.getConstraintLocator(const_cast<Expr *>(E)));
-    auto diagnosed = failure.diagnoseAsError();
-    assert(diagnosed && "failed to produce expected diagnostic");
-
-    for (auto cand : candidates) {
-      auto *candidate = cand.getDecl();
-      if (candidate && candidate != decl)
-        candidate->diagnose(diag::decl_declared_here, candidate->getFullName());
-    }
-    
-    return true;
-  }
-  
-  return false;
-}
-

lib/Sema/CalleeCandidateInfo.h

@@ -227,11 +227,6 @@ namespace swift {
     /// overloads.
     void suggestPotentialOverloads(SourceLoc loc, bool isResult = false);
 
-    /// Emit a diagnostic and return true if this is an error condition we can
-    /// handle uniformly.  This should be called after filtering the candidate
-    /// list.
-    bool diagnoseSimpleErrors(const Expr *E);
-    
     void dump(llvm::raw_ostream &os) const;
     SWIFT_DEBUG_DUMP;