Fix analyzer interpretation of 'ClassName?.staticMember'.

tests/language/conditional_property_assignment_test.dart

Index: tests/language/conditional_property_assignment_test.dart
diff --git a/tests/language/conditional_property_assignment_test.dart b/tests/language/conditional_property_assignment_test.dart
index 87e2bd08a350b696c73fbef9316052267b592505..12071984647dd6ab60e8b7d6b6e39f99010cb140 100644
--- a/tests/language/conditional_property_assignment_test.dart
+++ b/tests/language/conditional_property_assignment_test.dart
@@ -19,12 +19,13 @@ class B {}
 class C extends B {
   int v;
   C(this.v);
-  static var staticField;
+  static int staticInt;
 }
 
 class D {
   E v;
   D(this.v);
+  static E staticE;
 }
 
 class E {
@@ -50,9 +51,17 @@ main() {
   Expect.equals(null, nullC()?.v = bad()); /// 01: ok
   { C c = new C(1); Expect.equals(2, c?.v = 2); Expect.equals(2, c.v); } /// 02: ok
 
+  // C?.v = e2 is equivalent to C.v = e2.
+  { C.staticInt = 1; Expect.equals(2, C?.staticInt = 2); Expect.equals(2, C.staticInt); } /// 23: ok
+  { h.C.staticInt = 1; Expect.equals(2, h.C?.staticInt = 2); Expect.equals(2, h.C.staticInt); } /// 24: ok
+
   // The static type of e1?.v = e2 is the static type of e2.
   { D d = new D(new E()); G g = new G(); F f = (d?.v = g); Expect.identical(f, g); } /// 03: ok
   { D d = new D(new E()); E e = new G(); F f = (d?.v = e); Expect.identical(f, e); } /// 04: static type warning
+  { D.staticE = new E(); G g = new G(); F f = (D?.staticE = g); Expect.identical(f, g); } /// 25: ok
+  { h.D.staticE = new h.E(); h.G g = new h.G(); h.F f = (h.D?.staticE = g); Expect.identical(f, g); } /// 26: ok
+  { D.staticE = new E(); E e = new G(); F f = (D?.staticE = e); Expect.identical(f, e); } /// 27: static type warning
+  { h.D.staticE = new h.E(); h.E e = new h.G(); h.F f = (h.D?.staticE = e); Expect.identical(f, e); } /// 28: static type warning
 
   // Exactly the same static warnings that would be caused by e1.v = e2 are
   // also generated in the case of e1?.v = e2.
@@ -63,8 +72,13 @@ main() {
   Expect.equals(null, nullC()?.v += bad()); /// 07: ok
   { C c = new C(1); Expect.equals(3, c?.v += 2); Expect.equals(3, c.v); } /// 08: ok
 
+  // C?.v op= e2 is equivalent to C.v op= e2.
+  { C.staticInt = 1; Expect.equals(3, C?.staticInt += 2); Expect.equals(3, C?.staticInt); } /// 29: ok
+
   // The static type of e1?.v op= e2 is the static type of e1.v op e2.
   { D d = new D(new E()); F f = (d?.v += 1); Expect.identical(d.v, f); } /// 09: ok
+  { D.staticE = new E(); F f = (D?.staticE += 1); Expect.identical(D.staticE, f); } /// 30: ok
+  { h.D.staticE = new h.E(); h.F f = (h.D?.staticE += 1); Expect.identical(h.D.staticE, f); } /// 31: ok
 
   // Let T be the static type of e1 and let y be a fresh variable of type T.
   // Exactly the same static warnings that would be caused by y.v op e2 are
@@ -73,17 +87,12 @@ main() {
   { B b = new C(1); Expect.equals(3, b?.v += 2); Expect.equals(3, (b as C).v); } /// 11: static type warning
   { D d = new D(new E()); F f = (d?.v += nullC()); Expect.identical(d.v, f); } /// 12: static type warning
   { D d = new D(new E()); H h = (d?.v += 1); Expect.identical(d.v, h); } /// 13: static type warning
+  { D.staticE = new E(); F f = (D?.staticE += nullC()); Expect.identical(D.staticE, f); } /// 32: static type warning
+  { h.D.staticE = new h.E(); h.F f = (h.D?.staticE += h.nullC()); Expect.identical(h.D.staticE, f); } /// 33: static type warning
+  { D.staticE = new E(); H h = (D?.staticE += 1); Expect.identical(D.staticE, h); } /// 34: static type warning
+  { h.D.staticE = new h.E(); h.H hh = (h.D?.staticE += 1); Expect.identical(h.D.staticE, hh); } /// 35: static type warning
 
-  // Consequently, '?.' cannot be used to assign to static properties of
-  // classes.
-  Expect.throws(() => C?.staticField = null, noMethod); /// 14: static type warning
-  Expect.throws(() => C?.staticField += null, noMethod); /// 15: static type warning
-  Expect.throws(() => C?.staticField ??= null, noMethod); /// 16: static type warning
-  Expect.throws(() => h.C?.staticField = null, noMethod); /// 17: static type warning
-  Expect.throws(() => h.C?.staticField += null, noMethod); /// 18: static type warning
-  Expect.throws(() => h.C?.staticField ??= null, noMethod); /// 19: static type warning
-
-  // Nor can it be used to assign to toplevel properties in libraries imported
+  // '?.' cannot be used to assign to toplevel properties in libraries imported
   // via prefix.
   h?.topLevelVar = null; /// 20: compile-time error
   h?.topLevelVar += null; /// 21: compile-time error