From 25e623addbe2a6ddda585263dc3a2d9ba906a4b0 Mon Sep 17 00:00:00 2001
From: David Farler <dfarler@apple.com>
Date: Mon, 5 Dec 2016 19:34:02 -0800
Subject: [PATCH] Don't resolve a generic type parameter type from null
 environments

The generic environment of a GenericTypeToArchetypeResolver may be
`nullptr`, as returned by DeclContext::getGenericEnvironmentOfContext,
during prechecking of closure expressions at the necessarily non-generic
top level.

Fixes a couple of crashers.
---
 lib/Sema/TypeCheckGeneric.cpp                             | 5 ++++-
 .../099-swift-genericenvironment-maptypeintocontext.swift | 8 --------
 .../099-swift-genericenvironment-maptypeintocontext.swift | 7 +++++++
 ...466-segfault-0xc27624-0xc2741f-0xc25bb5-0xbcdbbb.swift | 2 +-
 4 files changed, 12 insertions(+), 10 deletions(-)
 delete mode 100644 validation-test/IDE/crashers/099-swift-genericenvironment-maptypeintocontext.swift
 create mode 100644 validation-test/IDE/crashers_fixed/099-swift-genericenvironment-maptypeintocontext.swift
 rename validation-test/{compiler_crashers => compiler_crashers_fixed}/28466-segfault-0xc27624-0xc2741f-0xc25bb5-0xbcdbbb.swift (87%)

diff --git a/lib/Sema/TypeCheckGeneric.cpp b/lib/Sema/TypeCheckGeneric.cpp
index d7a48d67cb778..657b29daeb3d3 100644
--- a/lib/Sema/TypeCheckGeneric.cpp
+++ b/lib/Sema/TypeCheckGeneric.cpp
@@ -90,7 +90,10 @@ Type GenericTypeToArchetypeResolver::resolveGenericTypeParamType(
   if (gpDecl->isInvalid())
     return ErrorType::get(gpDecl->getASTContext());
 
-  return GenericEnv->mapTypeIntoContext(gp);
+  if (auto *Env = GenericEnv)
+    return Env->mapTypeIntoContext(gp);
+
+  return ErrorType::get(gpDecl->getASTContext());
 }
 
 Type GenericTypeToArchetypeResolver::resolveDependentMemberType(
diff --git a/validation-test/IDE/crashers/099-swift-genericenvironment-maptypeintocontext.swift b/validation-test/IDE/crashers/099-swift-genericenvironment-maptypeintocontext.swift
deleted file mode 100644
index 9da90e1fa9d4a..0000000000000
--- a/validation-test/IDE/crashers/099-swift-genericenvironment-maptypeintocontext.swift
+++ /dev/null
@@ -1,8 +0,0 @@
-// RUN: not --crash %target-swift-ide-test -code-completion -code-completion-token=A -source-filename=%s
-// REQUIRES: asserts
-a{
-protocol e{
-typealias e
-extension{
-let b{let a={
-#^A^#func f:e
\ No newline at end of file
diff --git a/validation-test/IDE/crashers_fixed/099-swift-genericenvironment-maptypeintocontext.swift b/validation-test/IDE/crashers_fixed/099-swift-genericenvironment-maptypeintocontext.swift
new file mode 100644
index 0000000000000..37ac009d4a4a2
--- /dev/null
+++ b/validation-test/IDE/crashers_fixed/099-swift-genericenvironment-maptypeintocontext.swift
@@ -0,0 +1,7 @@
+// RUN: %target-swift-ide-test -code-completion -code-completion-token=A -source-filename=%s
+a{
+protocol e{
+typealias e
+extension{
+let b{let a={
+#^A^#func f:e
diff --git a/validation-test/compiler_crashers/28466-segfault-0xc27624-0xc2741f-0xc25bb5-0xbcdbbb.swift b/validation-test/compiler_crashers_fixed/28466-segfault-0xc27624-0xc2741f-0xc25bb5-0xbcdbbb.swift
similarity index 87%
rename from validation-test/compiler_crashers/28466-segfault-0xc27624-0xc2741f-0xc25bb5-0xbcdbbb.swift
rename to validation-test/compiler_crashers_fixed/28466-segfault-0xc27624-0xc2741f-0xc25bb5-0xbcdbbb.swift
index 74e4a168b2e0d..ff2d2222361f6 100644
--- a/validation-test/compiler_crashers/28466-segfault-0xc27624-0xc2741f-0xc25bb5-0xbcdbbb.swift
+++ b/validation-test/compiler_crashers_fixed/28466-segfault-0xc27624-0xc2741f-0xc25bb5-0xbcdbbb.swift
@@ -5,5 +5,5 @@
 // See https://swift.org/LICENSE.txt for license information
 // See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
 
-// RUN: not --crash %target-swift-frontend %s -emit-ir
+// RUN: not %target-swift-frontend %s -emit-ir
 {associatedtype b<T>func c:[T