[CS] Remove null pattern handling from getTypeForPattern

Push the only null case that can occur up into the
caller.

Author: hamishknight

lib/Sema/CSGen.cpp

@@ -2387,12 +2387,7 @@ namespace {
        bool bindPatternVarsOneWay,
        PatternBindingDecl *patternBinding = nullptr,
        unsigned patternBindingIndex = 0) {
-      // If there's no pattern, then we have an unknown subpattern. Create a
-      // type variable.
-      if (!pattern) {
-        return CS.createTypeVariable(CS.getConstraintLocator(locator),
-                                     TVO_CanBindToNoEscape);
-      }
+      assert(pattern);
 
       // Local function that must be called for each "return" throughout this
       // function, to set the type of the pattern.
@@ -4232,16 +4227,18 @@ bool ConstraintSystem::generateWrappedPropertyTypeConstraints(
 static bool generateInitPatternConstraints(ConstraintSystem &cs,
                                            SyntacticElementTarget target,
                                            Expr *initializer) {
-  auto pattern = target.getInitializationPattern();
   auto locator = cs.getConstraintLocator(
       initializer, LocatorPathElt::ContextualType(CTP_Initialization));
-  Type patternType = cs.generateConstraints(
-      pattern, locator, target.shouldBindPatternVarsOneWay(),
-      target.getInitializationPatternBindingDecl(),
-      target.getInitializationPatternBindingIndex());
 
-  if (!patternType)
-    return true;
+  Type patternType;
+  if (auto pattern = target.getInitializationPattern()) {
+    patternType = cs.generateConstraints(
+        pattern, locator, target.shouldBindPatternVarsOneWay(),
+        target.getInitializationPatternBindingDecl(),
+        target.getInitializationPatternBindingIndex());
+  } else {
+    patternType = cs.createTypeVariable(locator, TVO_CanBindToNoEscape);
+  }
 
   if (auto wrappedVar = target.getInitializationWrappedVar())
     return cs.generateWrappedPropertyTypeConstraints(