Sema: Don't generate OneWayEqual constraints for pattern bindings

I had to revert #78301 to fix
rdar://143338891.

This now brings back the change, but without deleting code; instead,
it's guarded by the -disable-optimized-restrictions flag. Once the
flag is removed, I will once again completely delete OneWayEqual
constraints.

Author: slavapestov

lib/Sema/CSGen.cpp

@@ -2704,7 +2704,8 @@ namespace {
         // type variable and a one-way constraint to assign it to either the
         // deduced type or the externally-imposed type.
         Type oneWayVarType;
-        if (bindPatternVarsOneWay) {
+        if (CS.getASTContext().TypeCheckerOpts.DisableOptimizedRestrictions &&
+            bindPatternVarsOneWay) {
           oneWayVarType = CS.createTypeVariable(
               CS.getConstraintLocator(locator), TVO_CanBindToNoEscape);
 

test/expr/closure/closures_swift6.swift

@@ -501,14 +501,18 @@ class TestGithubIssue70089 {
       }
 
       doVoidStuff { [weak self] in
-        doVoidStuff { [self] in
-          x += 1 // expected-error {{explicit use of 'self' is required when 'self' is optional, to make control flow explicit}} expected-note{{reference 'self?.' explicitly}}
+        doVoidStuff { [self] in // expected-error {{value of optional type 'TestGithubIssue70089?' must be unwrapped to a value of type 'TestGithubIssue70089'}}
+          // expected-note@-1 {{coalesce using '??' to provide a default when the optional value contains 'nil'}}
+          // expected-note@-2 {{force-unwrap using '!' to abort execution if the optional value contains 'nil'}}
+          x += 1
         }
       }
 
       doVoidStuff { [weak self] in
-        doVoidStuff { [self] in
-          self.x += 1 // expected-error {{value of optional type 'TestGithubIssue70089?' must be unwrapped to refer to member 'x' of wrapped base type 'TestGithubIssue70089'}} expected-note {{chain the optional using '?' to access member 'x' only for non-'nil' base values}} expected-note{{force-unwrap using '!' to abort execution if the optional value contains 'nil'}} 
+        doVoidStuff { [self] in // expected-error {{value of optional type 'TestGithubIssue70089?' must be unwrapped to a value of type 'TestGithubIssue70089'}}
+          // expected-note@-1 {{coalesce using '??' to provide a default when the optional value contains 'nil'}}
+          // expected-note@-2 {{force-unwrap using '!' to abort execution if the optional value contains 'nil'}}
+          self.x += 1
         }
       }