[CodeCompletion] Only analyze inner most context

Now that this passes all test cases we currently have. Stop analyzing
outer contexts because it may emit invalid context type.

Author: rintaro

lib/IDE/CodeCompletion.cpp

@@ -5427,21 +5427,20 @@ class CodeCompletionTypeContextAnalyzer {
       return false;
     DC->walkContext(Finder);
 
-    for (auto It = Finder.Ancestors.rbegin(); It != Finder.Ancestors.rend();
-         ++ It) {
-      if (auto Parent = It->getAsExpr()) {
-        analyzeExpr(Parent);
-      } else if (auto Parent = It->getAsStmt()) {
-        analyzeStmt(Parent);
-      } else if (auto Parent = It->getAsDecl()) {
-        analyzeDecl(Parent);
-      } else if (auto Parent = It->getAsPattern()) {
-        analyzePattern(Parent);
-      }
-      if (!PossibleTypes.empty() || !PossibleNames.empty())
-        return true;
-    }
-    return false;
+    if (Finder.Ancestors.empty())
+      return false;
+
+    auto &P = Finder.Ancestors.back();
+    if (auto Parent = P.getAsExpr()) {
+      analyzeExpr(Parent);
+    } else if (auto Parent = P.getAsStmt()) {
+      analyzeStmt(Parent);
+    } else if (auto Parent = P.getAsDecl()) {
+      analyzeDecl(Parent);
+    } else if (auto Parent = P.getAsPattern()) {
+      analyzePattern(Parent);
+    }
+    return (!PossibleTypes.empty() || !PossibleNames.empty());
   }
 
   ArrayRef<Type> getPossibleTypes() const { return PossibleTypes; }

test/IDE/complete_call_arg.swift

@@ -67,6 +67,9 @@
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=SUBSCRIPT_3 | %FileCheck %s -check-prefix=SUBSCRIPT_3
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=SUBSCRIPT_3_DOT | %FileCheck %s -check-prefix=SUBSCRIPT_3_DOT
 
+// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=ERRORCONTEXT_NESTED_1 | %FileCheck %s -check-prefix=ERRORCONTEXT_NESTED_1
+// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=ERRORCONTEXT_NESTED_2 | %FileCheck %s -check-prefix=ERRORCONTEXT_NESTED_1
+
 var i1 = 1
 var i2 = 2
 var oi1 : Int?
@@ -572,3 +575,17 @@ func testSubscript(obj: HasSubscript, intValue: Int, strValue: String) {
 // SUBSCRIPT_3_DOT-DAG: Decl[Constructor]/CurrNominal/TypeRelation[Identical]: init({#(c): Character#})[#String#]; name=init(c: Character)
 
 }
+
+func testNestedContext() {
+  func foo(_ x: Int) {}
+  func bar(_ y: TypeInvalid) -> Int {}
+
+  let _ = foo(bar(#^ERRORCONTEXT_NESTED_1^#))
+// ERRORCONTEXT_NESTED_1: Begin completions
+// ERRORCONTEXT_NESTED_1-DAG: Decl[GlobalVar]/CurrModule: i1[#Int#]; name=i1
+// ERRORCONTEXT_NESTED_1-DAG: Decl[GlobalVar]/CurrModule: i2[#Int#]; name=i2
+// ERRORCONTEXT_NESTED_1-NOT: TypeRelation[Identical]
+
+  for _ in [bar(#^ERRORCONTEXT_NESTED_2^#)] {}
+// Same as ERRORCONTEXT_NESTED_1.
+}