AST: Fix Substitution::subst to substitute associated types from conformance witnesses instead of by name.

Fixes a crash when property behavior uses are run through the specializer, since they set up associated type conformances that are not recoverable by name lookup.

Author: jckarter

lib/AST/Substitution.cpp

@@ -43,9 +43,7 @@ getSubstitutionMaps(GenericParamList *context,
     // Save the conformances from the substitution so that we can substitute
     // them into substitutions that map between archetypes.
     conformanceMap[arch] = sub.getConformances();
-
-    if (arch->isPrimary())
-      typeMap[arch] = sub.getReplacement();
+    typeMap[arch] = sub.getReplacement();
   }
   assert(subs.empty() && "did not use all substitutions?!");
 }

test/Interpreter/property_behavior.swift

@@ -4,12 +4,6 @@
 // RUN: %target-run %t/a.out
 // REQUIRES: executable_test
 
-// TODO: Fix specializer to substitute using conformance type witnesses instead
-// of name lookup
-
-// XFAIL: swift_test_mode_optimize
-// XFAIL: swift_test_mode_optimize_unchecked
-
 import StdlibUnittest
 
 protocol delayedImmutable {

test/SILOptimizer/specialize_property_behavior.swift

@@ -0,0 +1,25 @@
+// RUN: %target-swift-frontend -emit-sil -parse-as-library -O -enable-experimental-property-behaviors %s | FileCheck %s
+
+@inline(never) func whatever<T>() -> T { fatalError("") }
+
+protocol lazzy {
+  associatedtype Value
+}
+extension lazzy {
+  var value: Value {
+    return whatever()
+  }
+}
+
+struct Foo {
+  var [lazzy] x: Int
+
+  init() {}
+}
+
+public func exercise() {
+  _ = Foo().x
+}
+
+// CHECK-LABEL: sil @_TF28specialize_property_behavior8exerciseFT_T_
+// CHECK:         function_ref @_TTSg5Si___TF28specialize_property_behavior8whateverurFT_x