Re-apply "Playground Transform: Fix assertion failure in generic code" (#6747)

This regression was introduced in the following commit:
<6cbb494>

Fixes <rdar://problem/29935266>.

Author: slavapestov

lib/Sema/PlaygroundTransform.cpp

@@ -742,8 +742,7 @@ class Instrumenter : InstrumenterBase {
                               /*IsCaptureList*/false, SourceLoc(),
                               Context.getIdentifier(NameBuf),
                               MaybeLoadInitExpr->getType(), TypeCheckDC);
-
-    VD->setInterfaceType(VD->getType());
+    VD->setInterfaceType(TypeCheckDC->mapTypeOutOfContext(VD->getType()));
     VD->setImplicit();
 
     NamedPattern *NP = new (Context) NamedPattern(VD, /*implicit*/ true);

test/PlaygroundTransform/generics.swift

@@ -0,0 +1,35 @@
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// RUN: cp %s %t/main.swift
+// RUN: %target-build-swift -Xfrontend -playground -Xfrontend -debugger-support -o %t/main %S/Inputs/PlaygroundsRuntime.swift %t/main.swift
+// RUN: %target-run %t/main | %FileCheck %s
+// RUN: %target-build-swift -Xfrontend -pc-macro -Xfrontend -playground -Xfrontend -debugger-support -o %t/main %S/Inputs/PlaygroundsRuntime.swift %S/Inputs/SilentPCMacroRuntime.swift %t/main.swift
+// RUN: %target-run %t/main | %FileCheck %s
+// REQUIRES: executable_test
+
+func id<T>(_ t: T) -> T {
+  return t
+}
+
+for i in 0..<3 {
+  _ = id(i)
+}
+
+// CHECK:      $builtin_log_scope_entry
+// CHECK-NEXT: $builtin_log_scope_entry
+// CHECK-NEXT: $builtin_log[='0']
+// CHECK-NEXT: $builtin_log_scope_exit
+// CHECK-NEXT: $builtin_log[='0']
+// CHECK-NEXT: $builtin_log_scope_exit
+// CHECK-NEXT: $builtin_log_scope_entry
+// CHECK-NEXT: $builtin_log_scope_entry
+// CHECK-NEXT: $builtin_log[='1']
+// CHECK-NEXT: $builtin_log_scope_exit
+// CHECK-NEXT: $builtin_log[='1']
+// CHECK-NEXT: $builtin_log_scope_exit
+// CHECK-NEXT: $builtin_log_scope_entry
+// CHECK-NEXT: $builtin_log_scope_entry
+// CHECK-NEXT: $builtin_log[='2']
+// CHECK-NEXT: $builtin_log_scope_exit
+// CHECK-NEXT: $builtin_log[='2']
+// CHECK-NEXT: $builtin_log_scope_exit