AST: Assert if attempting to do conformance lookup table things on a protocol

Unlike structs, enums and classes, protocols should not have a
conformance lookup table with normal conformances in it.

Author: slavapestov

lib/AST/ConformanceLookupTable.cpp

@@ -874,13 +874,18 @@ ConformanceLookupTable::getConformance(NominalTypeDecl *nominal,
     entry->Conformance =
         ctx.getInheritedConformance(type, inheritedConformance.getConcrete());
   } else {
-    // Create or find the normal conformance.
+    // Protocols don't have conformance lookup tables. Self-conformance is
+    // handled directly in lookupConformance().
+    assert(!isa<ProtocolDecl>(conformingNominal));
+    assert(!isa<ProtocolDecl>(conformingDC->getSelfNominalTypeDecl()));
     Type conformingType = conformingDC->getSelfInterfaceType();
+
     SourceLoc conformanceLoc
       = conformingNominal == conformingDC
           ? conformingNominal->getLoc()
           : cast<ExtensionDecl>(conformingDC)->getLoc();
 
+    // Create or find the normal conformance.
     auto normalConf =
         ctx.getConformance(conformingType, protocol, conformanceLoc,
                            conformingDC, ProtocolConformanceState::Incomplete,

lib/AST/ProtocolConformance.cpp

@@ -1224,6 +1224,9 @@ ProtocolConformance::getInheritedConformance(ProtocolDecl *protocol) const {
 
 #pragma mark Protocol conformance lookup
 void NominalTypeDecl::prepareConformanceTable() const {
+  assert(!isa<ProtocolDecl>(this) &&
+         "Protocols don't have a conformance table");
+
   if (ConformanceTable)
     return;
 
@@ -1292,6 +1295,10 @@ void NominalTypeDecl::prepareConformanceTable() const {
 bool NominalTypeDecl::lookupConformance(
        ProtocolDecl *protocol,
        SmallVectorImpl<ProtocolConformance *> &conformances) const {
+  assert(!isa<ProtocolDecl>(this) &&
+         "Self-conformances are only found by the higher-level "
+         "ModuleDecl::lookupConformance() entry point");
+
   prepareConformanceTable();
   return ConformanceTable->lookupConformance(
            const_cast<NominalTypeDecl *>(this),
@@ -1301,6 +1308,10 @@ bool NominalTypeDecl::lookupConformance(
 
 SmallVector<ProtocolDecl *, 2>
 NominalTypeDecl::getAllProtocols(bool sorted) const {
+  assert(!isa<ProtocolDecl>(this) &&
+         "For inherited protocols, use ProtocolDecl::inheritsFrom() or "
+         "ProtocolDecl::getInheritedProtocols()");
+
   prepareConformanceTable();
   SmallVector<ProtocolDecl *, 2> result;
   ConformanceTable->getAllProtocols(const_cast<NominalTypeDecl *>(this), result,