IRGen: Deal with broken conformance in the AST

rdar://57876556

Author: aschwaighofer

lib/IRGen/GenProto.cpp

@@ -913,6 +913,11 @@ static bool isDependentConformance(
 
     auto assocConformance =
       conformance->getAssociatedConformance(req.getFirstType(), assocProtocol);
+
+    // We migh be presented with a broken AST.
+    if (assocConformance.isInvalid())
+      return false;
+
     if (assocConformance.isAbstract() ||
         isDependentConformance(IGM,
                                assocConformance.getConcrete()

test/IRGen/Inputs/batchmode_errors.swift

@@ -12,3 +12,11 @@ class SomeClass {
   var x : AnotherClass2? = nil
 }
 
+protocol P {}
+protocol WithAssoc {
+  associatedtype AssocType : P
+}
+
+struct BuggyConformer : WithAssoc {
+  typealias AssocType = Int
+}

test/IRGen/batchmode_ast_errors.swift

@@ -9,3 +9,10 @@
 extension SomeClass : SomeProto {
   func conform() {}
 }
+
+func genericParam<T: WithAssoc>(_ t: T) {
+}
+
+func testBuggyGenericParam() {
+   genericParam(BuggyConformer())
+}