[CSSimplify] When trying to simplify bind with error type fail gracefully

lib/Sema/CSSimplify.cpp

@@ -1488,6 +1488,16 @@ ConstraintSystem::matchTypesBindTypeVar(
   if (!isBindable(typeVar, type))
     return formUnsolvedResult();
 
+  // Since member lookup doesn't check requirements
+  // it might sometimes return types which are not
+  // visible in the current context e.g. typealias
+  // defined in constrained extension, substitution
+  // of which might produce error type for base, so
+  // assignement should thead lightly and just fail
+  // if it encounters such types.
+  if (type->hasError())
+    return getTypeMatchFailure(locator);
+
   // Equal constraints allow mixed LValue/RValue bindings, but
   // if we bind a type to a type variable that can bind to
   // LValues as part of simplifying the Equal constraint we may

validation-test/compiler_crashers_2/0130-sr5013.swift → validation-test/compiler_crashers_2_fixed/0130-sr5013.swift

@@ -1,5 +1,5 @@
-// RUN: not --crash %target-swift-frontend -typecheck %s
-// REQUIRES: asserts
+// RUN: not %target-swift-frontend -typecheck %s
+
 
 protocol A {
     associatedtype B

validation-test/compiler_crashers_2_fixed/0159-rdar39931339.swift

@@ -0,0 +1,39 @@
+// RUN: %target-typecheck-verify-swift
+
+protocol P0 {
+    associatedtype A
+}
+
+protocol P1 {
+  associatedtype B : P3 = S0<S2>
+  associatedtype C = ()
+}
+
+protocol P2 {
+  associatedtype D : P1
+  associatedtype E : P3 = S0<S2>
+}
+
+protocol P3 : P0 where A : P2 {}
+
+struct S0<T> : P0 {
+    typealias A = T
+}
+
+extension S0 : P3 where T : P2 {}
+
+struct S2 : P2 {
+  struct D : P1 {
+    let value: S2
+  }
+}
+
+extension P1 where C : P2 {
+  typealias B = C.E
+}
+
+extension P3 {
+  func foo() {
+    _ = A.D.B.self
+  }
+}

validation-test/compiler_crashers/28826-type-haserror-should-not-be-assigning-a-type-involving-errortype.swift → validation-test/compiler_crashers_fixed/28826-type-haserror-should-not-be-assigning-a-type-involving-errortype.swift

@@ -5,6 +5,6 @@
 // See https://swift.org/LICENSE.txt for license information
 // See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
 
-// REQUIRES: asserts
-// RUN: not --crash %target-swift-frontend %s -emit-ir
+
+// RUN: not %target-swift-frontend %s -emit-ir
 protocol A{{}protocol a{extension{class a<a{let d=a(class a<P

validation-test/compiler_crashers/28828-unreachable-executed-at-swift-lib-ast-type-cpp-3237.swift → validation-test/compiler_crashers_fixed/28828-unreachable-executed-at-swift-lib-ast-type-cpp-3237.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
 class a<a{class a{extension{protocol P{class a:a{func a:Self.a