[QoI] Improve fix-it when renamed method has contextual member lookup argument

Currently we generate incorrect fix-it in situations where we
have contextual member lookup as one of the arguments.

Resolves: rdar://problem/32526620

Author: xedin

lib/Sema/TypeCheckAvailability.cpp

@@ -1628,7 +1628,26 @@ static void fixItAvailableAttrRename(TypeChecker &TC,
     SmallString<64> selfReplace;
     if (needsParens)
       selfReplace.push_back('(');
-    selfReplace += sourceMgr.extractText(selfExprRange);
+
+    // If the base is contextual member lookup and we know the type,
+    // let's just prepend it, otherwise we'll end up with an incorrect fix-it.
+    auto base = sourceMgr.extractText(selfExprRange);
+    if (!base.empty() && base.front() == '.') {
+      auto newName = attr->Rename;
+      // If this is not a rename, let's not
+      // even try to emit a fix-it because
+      // it's going to be invalid.
+      if (newName.empty())
+        return;
+
+      auto parts = newName.split('.');
+      auto nominalName = parts.first;
+      assert(!nominalName.empty());
+
+      selfReplace += nominalName;
+    }
+
+    selfReplace += base;
     if (needsParens)
       selfReplace.push_back(')');
     selfReplace.push_back('.');

test/attr/attr_availability.swift

@@ -783,3 +783,25 @@ func testVariadic() {
   variadic3(1, b: 2, 3, d: "test") // expected-error {{'variadic3(_:b:c:d:)' has been renamed to 'after(x:_:y:z:)'}} {{3-12=after}} {{13-13=x: }} {{16-19=}} {{25-26=z}} {{none}}
   variadic3(1, d:"test") // expected-error {{'variadic3(_:b:c:d:)' has been renamed to 'after(x:_:y:z:)'}} {{3-12=after}} {{13-13=x: }} {{16-17=z}} {{none}}
 }
+
+enum E_32526620 {
+  case foo
+  case bar
+
+  func set() {}
+}
+
+@available(*, unavailable, renamed: "E_32526620.set(self:)")
+func rdar32526620_1(a: E_32526620) {} // expected-note {{here}}
+rdar32526620_1(a: .foo)
+// expected-error@-1 {{'rdar32526620_1(a:)' has been replaced by instance method 'E_32526620.set()'}} {{1-15=E_32526620.foo.set}} {{16-23=}}
+
+@available(*, unavailable, renamed: "E_32526620.set(a:self:)")
+func rdar32526620_2(a: Int, b: E_32526620) {} // expected-note {{here}}
+rdar32526620_2(a: 42, b: .bar)
+// expected-error@-1 {{'rdar32526620_2(a:b:)' has been replaced by instance method 'E_32526620.set(a:)'}} {{1-15=E_32526620.bar.set}} {{21-30=}}
+
+@available(*, unavailable, renamed: "E_32526620.set(a:self:c:)")
+func rdar32526620_3(a: Int, b: E_32526620, c: String) {} // expected-note {{here}}
+rdar32526620_3(a: 42, b: .bar, c: "question")
+// expected-error@-1 {{'rdar32526620_3(a:b:c:)' has been replaced by instance method 'E_32526620.set(a:c:)'}} {{1-15=E_32526620.bar.set}} {{23-32=}}