[CodeCompletion] Always look into decls to find the parsed expression

In fast completion scenario, 'AbstractFunctionDecl' may have the body
from the different file than the decl itself. Thay may confuses source
range checking.

As a workaround, always look into decls regardless of the range. This
should not regress the speed of the searching much because
statements/expressions (including nested function bodies) in the decl
is still skipped if it's outside the range.

rdar://problem/58098222

Author: rintaro

lib/IDE/ExprContextAnalysis.cpp

@@ -161,8 +161,6 @@ class ExprFinder : public ASTWalker {
     return {isInterstingRange(S), S};
   }
 
-  bool walkToDeclPre(Decl *D) override { return isInterstingRange(D); }
-
   bool walkToTypeLocPre(TypeLoc &TL) override { return false; }
   bool walkToTypeReprPre(TypeRepr *T) override { return false; }
 };

test/SourceKit/CodeComplete/complete_sequence_bodyrange.swift

@@ -0,0 +1,57 @@
+class TestChain {
+  class Child {
+    var value: Struct1?
+  }
+  class Struct1 {
+    var value: Struct2
+  }
+  class Struct2 {
+    var prop1: Int
+    var prop2: Int
+  }
+
+  var child: Child!
+
+  func foo() {
+    let _ = child.value?.value.
+  }
+}
+
+// rdar://problem/58098222
+
+// RUN: %sourcekitd-test \
+// RUN:   -req=complete -req-opts=reuseastcontext=1 -pos=16:32 %s -async -- %s == \
+// RUN:   -req=complete -req-opts=reuseastcontext=1 -pos=16:32 %s -async -- %s == \
+// RUN:   -req=complete -req-opts=reuseastcontext=1 -pos=16:32 %s -async -- %s == \
+// RUN:   -req=complete -req-opts=reuseastcontext=1 -pos=16:32 %s -async -- %s == \
+// RUN:   -req=complete -req-opts=reuseastcontext=1 -pos=16:32 %s -async -- %s == \
+// RUN:   -req=complete -req-opts=reuseastcontext=1 -pos=16:32 %s -async -- %s == \
+// RUN:   -req=complete -req-opts=reuseastcontext=1 -pos=16:32 %s -async -- %s == \
+// RUN:   -req=complete -req-opts=reuseastcontext=1 -pos=16:32 %s -async -- %s == \
+// RUN:   -req=complete -req-opts=reuseastcontext=1 -pos=16:32 %s -async -- %s == \
+// RUN:   -req=complete -req-opts=reuseastcontext=1 -pos=16:32 %s -async -- %s | %FileCheck %s
+
+// CHECK-NOT: key.name: "prop1"
+// CHECK-NOT: key.name: "prop2"
+// CHECK: key.name: "prop1",
+// CHECK: key.name: "prop2",
+// CHECK: key.name: "prop1",
+// CHECK: key.name: "prop2",
+// CHECK: key.name: "prop1",
+// CHECK: key.name: "prop2",
+// CHECK: key.name: "prop1",
+// CHECK: key.name: "prop2",
+// CHECK: key.name: "prop1",
+// CHECK: key.name: "prop2",
+// CHECK: key.name: "prop1",
+// CHECK: key.name: "prop2",
+// CHECK: key.name: "prop1",
+// CHECK: key.name: "prop2",
+// CHECK: key.name: "prop1",
+// CHECK: key.name: "prop2",
+// CHECK: key.name: "prop1",
+// CHECK: key.name: "prop2",
+// CHECK: key.name: "prop1",
+// CHECK: key.name: "prop2",
+// CHECK-NOT: key.name: "prop1"
+// CHECK-NOT: key.name: "prop2"