[ASTScopes] Remove ErrorExpr check from condition scope expansion

This appears unnecessary and incorrectly meant the ErrorExpr would
be placed outside the condition, meaning we could find the binding
in its own initializer.

Author: hamishknight

lib/AST/ASTScopeCreation.cpp

@@ -959,11 +959,8 @@ AnnotatedInsertionPoint
 ConditionalClausePatternUseScope::expandAScopeThatCreatesANewInsertionPoint(
     ScopeCreator &scopeCreator) {
   auto *initializer = sec.getInitializer();
-  if (!isa<ErrorExpr>(initializer)) {
-    scopeCreator
-      .constructExpandAndInsert<ConditionalClauseInitializerScope>(
-        this, initializer);
-    }
+  scopeCreator.constructExpandAndInsert<ConditionalClauseInitializerScope>(
+      this, initializer);
 
   return {this,
           "Succeeding code must be in scope of conditional clause pattern bindings"};

validation-test/compiler_crashers_fixed/TypeVarRefCollector-walkToStmtPre-5c070f.swift

@@ -0,0 +1,7 @@
+// {"kind":"typecheck","signature":"swift::constraints::TypeVarRefCollector::walkToStmtPre(swift::Stmt*)","signatureAssert":"Assertion failed: (result), function getClosureType"}
+// RUN: not %target-swift-frontend -typecheck %s
+{
+  guard let a = (a  if{
+    return
+  }
+) "