Clang: Fix dot-arrow-correction for zero results

If there are no completion items, do not add snippets since these will
otherwise pop-up at undesired positions, e.g. when:

 1) Typing float/doubles: 0.
 2) Typing file suffix in include directives: #include "stdio.

Task-number: QTCREATORBUG-16188
Change-Id: Ie1c29826dc62dc447b2ff57b0c5537eb9d9511ef
Reviewed-by: David Schulz <david.schulz@theqtcompany.com>

src/plugins/clangcodemodel/clangcompletionassistprocessor.cpp

@@ -613,7 +613,7 @@ void ClangCompletionAssistProcessor::handleAvailableCompletions(
     QTC_CHECK(m_completions.isEmpty());
 
     m_completions = toAssistProposalItems(completions);
-    if (m_addSnippets)
+    if (m_addSnippets && !m_completions.isEmpty())
         addSnippets();
 
     setAsyncProposalAvailable(createProposal(neededCorrection));

src/plugins/clangcodemodel/test/clangcodecompletion_test.cpp

@@ -932,18 +932,28 @@ void ClangCodeCompletionTest::testCompleteConstructorAndFallbackToGlobalCompleti
     QVERIFY(!hasSnippet(t.proposal, "class"));
 }
 
+// Explicitly Inserting The Dot
+// ----------------------------
+// Inserting the dot for is important since it will send the editor
+// content to the backend and thus generate an unsaved file on the backend
+// side. The unsaved file enables us to do the dot to arrow correction.
+
 void ClangCodeCompletionTest::testCompleteWithDotToArrowCorrection()
 {
-    // Inserting the dot for this test is important since it will send the editor
-    // content to the backend and thus generate an unsaved file on the backend
-    // side. The unsaved file enables us to do the dot to arrow correction.
-
     ProjectLessCompletionTest t("dotToArrowCorrection.cpp",
-                                QStringLiteral("."));
+                                QStringLiteral(".")); // See above "Explicitly Inserting The Dot"
 
     QVERIFY(hasItem(t.proposal, "member"));
 }
 
+void ClangCodeCompletionTest::testDontCompleteWithDotToArrowCorrectionForFloats()
+{
+    ProjectLessCompletionTest t("noDotToArrowCorrectionForFloats.cpp",
+                                QStringLiteral(".")); // See above "Explicitly Inserting The Dot"
+
+    QCOMPARE(t.proposal->size(), 0);
+}
+
 void ClangCodeCompletionTest::testCompleteProjectDependingCode()
 {
     const TestDocument testDocument("completionWithProject.cpp");

src/plugins/clangcodemodel/test/clangcodecompletion_test.h

@@ -49,6 +49,7 @@ private slots:
     void testCompleteConstructorAndFallbackToGlobalCompletion();
 
     void testCompleteWithDotToArrowCorrection();
+    void testDontCompleteWithDotToArrowCorrectionForFloats();
 
     void testCompleteProjectDependingCode();
     void testCompleteProjectDependingCodeAfterChangingProject();

src/plugins/clangcodemodel/test/data/clangtestdata.qrc

@@ -22,5 +22,6 @@
         <file>objc_messages_3.mm</file>
         <file>preprocessorKeywordsCompletion.cpp</file>
         <file>dotToArrowCorrection.cpp</file>
+        <file>noDotToArrowCorrectionForFloats.cpp</file>
     </qresource>
 </RCC>

src/plugins/clangcodemodel/test/data/noDotToArrowCorrectionForFloats.cpp

@@ -0,0 +1,4 @@
+void f()
+{
+    0 /* COMPLETE HERE */
+}