[code-completion] Improve robustness of Solution::computeSubstitutions and check if OpenedTypes contains the provided locator.

Fixes validation-test/IDE/crashers/103-swift-constraints-solution-resolvelocatortodecl.swift.

Author: akyrtzi

lib/Sema/CSApply.cpp

@@ -85,18 +85,19 @@ Type Solution::computeSubstitutions(
        SmallVectorImpl<Substitution> &result) const {
   auto &tc = getConstraintSystem().getTypeChecker();
 
+  // Produce the concrete form of the opened type.
+  Type type = simplifyType(tc, openedType);
+
   // Gather the substitutions from dependent types to concrete types.
   auto openedTypes = OpenedTypes.find(locator);
-  assert(openedTypes != OpenedTypes.end() && "Missing opened type information");
+  if (openedTypes == OpenedTypes.end())
+    return type;
   TypeSubstitutionMap subs;
   for (const auto &opened : openedTypes->second) {
     subs[opened.first->castTo<GenericTypeParamType>()] =
       getFixedType(opened.second);
   }
 
-  // Produce the concrete form of the opened type.
-  Type type = simplifyType(tc, openedType);
-
   auto mod = getConstraintSystem().DC->getParentModule();
   GenericSignature *sig;
   if (auto genericFn = origType->getAs<GenericFunctionType>()) {

validation-test/IDE/crashers/103-swift-constraints-solution-resolvelocatortodecl.swift

@@ -0,0 +1,3 @@
+// RUN: %target-swift-ide-test -code-completion -code-completion-token=A -source-filename=%s
+protocol b
+func b{b#^A^#