[IDE] Make sure to disable typo-correction when doing code-completion.

Typo-correction can be expensive and we don't need it for code-completion.

Author: akyrtzi

include/swift/Frontend/Frontend.h

@@ -263,6 +263,8 @@ class CompilerInvocation {
     assert(Buf);
     CodeCompletionBuffer = Buf;
     CodeCompletionOffset = Offset;
+    // We don't need typo-correction for code-completion.
+    LangOpts.DisableTypoCorrection = true;
   }
 
   std::pair<llvm::MemoryBuffer *, unsigned> getCodeCompletionPoint() const {

test/IDE/complete_without_typo_correction.swift

@@ -0,0 +1,13 @@
+// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=HERE -code-completion-diagnostics 2> %t.err.txt
+// RUN: %FileCheck %s -input-file=%t.err.txt
+
+// CHECK: use of unresolved identifier 'foo11'
+// CHECK-NOT: did you mean
+
+func foo12() -> Int { return 0 }
+
+class C {
+  var p = foo11()
+}
+
+C().#^HERE^#