[CS] Fix a couple of constraints in getTypeForPattern

The TypedPattern and IsPattern constraints were
incorrectly written, with conversions propagating
out of the patterns, when really conversions
ought to propagate into patterns. In any case, it
seems like we really want equality here. Fix the
constraints to use equality, and have the cast
constraint operate on the external pattern type
instead of the subpattern type.

Author: hamishknight

lib/Sema/CSGen.cpp

@@ -2714,7 +2714,7 @@ namespace {
           return Type();
 
         CS.addConstraint(
-            ConstraintKind::Conversion, subPatternType, openedType,
+            ConstraintKind::Equal, subPatternType, openedType,
             locator.withPathElement(LocatorPathElt::PatternMatch(pattern)));
 
         // FIXME [OPAQUE SUPPORT]: the distinction between where we want opaque
@@ -2805,21 +2805,6 @@ namespace {
             locator.withPathElement(LocatorPathElt::PatternMatch(pattern)));
         if (!castType) return Type();
 
-        auto *subPattern = isPattern->getSubPattern();
-        Type subPatternType = getTypeForPattern(
-            subPattern,
-            locator.withPathElement(LocatorPathElt::PatternMatch(subPattern)),
-            castType, bindPatternVarsOneWay);
-
-        if (!subPatternType)
-          return Type();
-
-        // Make sure we can cast from the subpattern type to the type we're
-        // checking; if it's impossible, fail.
-        CS.addConstraint(
-            ConstraintKind::CheckedCast, subPatternType, castType,
-            locator.withPathElement(LocatorPathElt::PatternMatch(pattern)));
-
         // Allow `is` pattern to infer type from context which is then going
         // to be propaged down to its sub-pattern via conversion. This enables
         // correct handling of patterns like `_ as Foo` where `_` would
@@ -2828,9 +2813,23 @@ namespace {
         auto isType =
             CS.createTypeVariable(CS.getConstraintLocator(pattern),
                                   TVO_CanBindToNoEscape | TVO_CanBindToHole);
+
+        // Make sure we can cast from the subpattern type to the type we're
+        // checking; if it's impossible, fail.
         CS.addConstraint(
-            ConstraintKind::Conversion, subPatternType, isType,
+            ConstraintKind::CheckedCast, isType, castType,
             locator.withPathElement(LocatorPathElt::PatternMatch(pattern)));
+
+        if (auto *subPattern = isPattern->getSubPattern()) {
+          auto subPatternType = getTypeForPattern(
+              subPattern,
+              locator.withPathElement(LocatorPathElt::PatternMatch(subPattern)),
+              castType, bindPatternVarsOneWay);
+
+          CS.addConstraint(
+              ConstraintKind::Equal, subPatternType, castType,
+              locator.withPathElement(LocatorPathElt::PatternMatch(pattern)));
+        }
         return setType(isType);
       }
 

lib/Sema/CSSimplify.cpp

@@ -14821,8 +14821,7 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyFixConstraint(
     if (recordFix(fix))
       return SolutionKind::Error;
 
-    (void)matchTypes(type1, OptionalType::get(type2),
-                     ConstraintKind::Conversion,
+    (void)matchTypes(type1, OptionalType::get(type2), ConstraintKind::Equal,
                      TypeMatchFlags::TMF_ApplyingFix, locator);
 
     return SolutionKind::Solved;

test/Parse/matching_patterns.swift

@@ -307,6 +307,7 @@ do {
   while case let _ as [Derived] = arr {}
   // expected-warning@-1 {{'let' pattern has no effect; sub-pattern didn't bind any variables}}
 
+  // https://github.com/apple/swift/issues/61850
   for case _ as [Derived] in [arr] {}
 
   if case is [Derived] = arr {}

test/Parse/matching_patterns_reference_bindings.swift

@@ -328,6 +328,7 @@ do {
   while case let _ as [Derived] = arr {}
   // expected-warning@-1 {{'let' pattern has no effect; sub-pattern didn't bind any variables}}
 
+  // https://github.com/apple/swift/issues/61850
   for case _ as [Derived] in [arr] {}
 
   if case is [Derived] = arr {}

test/decl/var/property_wrappers.swift

@@ -1338,7 +1338,7 @@ struct MissingPropertyWrapperUnwrap {
 
 struct InvalidPropertyDelegateUse {
   // TODO(diagnostics): We need to a tailored diagnostic for extraneous arguments in property delegate initialization
-  @Foo var x: Int = 42 // expected-error@:21 {{argument passed to call that takes no arguments}}
+  @Foo var x: Int = 42 // expected-error@:21 {{extra argument 'wrappedValue' in call}}
 
   func test() {
     self.x.foo() // expected-error {{value of type 'Int' has no member 'foo'}}