Add type inference for assignments to properties.

pkg/front_end/testcases/inference/infer_assign_to_property_null_aware.dart.direct.expect

Index: pkg/front_end/testcases/inference/infer_assign_to_property_null_aware.dart.direct.expect
diff --git a/pkg/front_end/testcases/inference/infer_assign_to_property_null_aware.dart.direct.expect b/pkg/front_end/testcases/inference/infer_assign_to_property_null_aware.dart.direct.expect
new file mode 100644
index 0000000000000000000000000000000000000000..1d927ad57a9ff6c3122648fdac95b4e772dbacdd
--- /dev/null
+++ b/pkg/front_end/testcases/inference/infer_assign_to_property_null_aware.dart.direct.expect
@@ -0,0 +1,52 @@
+library test;
+import self as self;
+import "dart:core" as core;
+
+class A extends core::Object {
+  constructor •() → void
+    : super core::Object::•()
+    ;
+}
+class B extends self::A {
+  constructor •() → void
+    : super self::A::•()
+    ;
+  operator +(self::C v) → self::A
+    return null;
+  operator -(core::int i) → self::B
+    return null;
+  operator *(self::B v) → self::B
+    return null;
+  operator &(self::A v) → self::C
+    return null;
+}
+class C extends self::B {
+  constructor •() → void
+    : super self::B::•()
+    ;
+}
+class Test extends core::Object {
+  field self::B member = null;
+  constructor •() → void
+    : super core::Object::•()
+    ;
+  static method test(self::Test t) → void {
+    let final dynamic #t1 = t in #t1.==(null) ? null : #t1.member = self::f();
+    let final dynamic #t2 = t in #t2.==(null) ? null : #t2.member.==(null) ? #t2.member = self::f() : null;
+    let final dynamic #t3 = t in #t3.==(null) ? null : #t3.member = #t3.member.+(self::f());
+    let final dynamic #t4 = t in #t4.==(null) ? null : #t4.member = #t4.member.*(self::f());
+    let final dynamic #t5 = t in #t5.==(null) ? null : #t5.member = #t5.member.&(self::f());
+    let final dynamic #t6 = t in #t6.==(null) ? null : #t6.member = #t6.member.-(1);
+    let final dynamic #t7 = t in #t7.==(null) ? null : #t7.member = #t7.member.-(1);
+    dynamic v1 = let final dynamic #t8 = t in #t8.==(null) ? null : #t8.member = self::f();
+    dynamic v2 = let final dynamic #t9 = t in #t9.==(null) ? null : let final dynamic #t10 = #t9.member in #t10.==(null) ? #t9.member = self::f() : #t10;
+    dynamic v3 = let final dynamic #t11 = t in #t11.==(null) ? null : #t11.member = #t11.member.+(self::f());
+    dynamic v4 = let final dynamic #t12 = t in #t12.==(null) ? null : #t12.member = #t12.member.*(self::f());
+    dynamic v5 = let final dynamic #t13 = t in #t13.==(null) ? null : #t13.member = #t13.member.&(self::f());
+    dynamic v6 = let final dynamic #t14 = t in #t14.==(null) ? null : #t14.member = #t14.member.-(1);
+    dynamic v7 = let final dynamic #t15 = t in #t15.==(null) ? null : let final dynamic #t16 = #t15.member in let final dynamic #t17 = #t15.member = #t16.-(1) in #t16;
+  }
+}
+static method f() → dynamic
+  return null;
+static method main() → dynamic {}