Clang: Show full completion match first

If prefix is equal to some completion then show it
before anything else.

Task-number: QTCREATORBUG-15445
Change-Id: I976da4a829b818e843d31a76d2818eb5bbedda93
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/plugins/texteditor/codeassist/assistproposaliteminterface.h

@@ -47,9 +47,10 @@ public:
     // We compare proposals by enum values, be careful changing their values
     enum class PrefixMatch
     {
-        Exact = 0,
-        Lower = 1,
-        None = 2
+        Full = 0,
+        Exact = 1,
+        Lower = 2,
+        None = 3
     };
 
     AssistProposalItemInterface() = default;

src/plugins/texteditor/codeassist/genericproposalmodel.cpp

@@ -316,7 +316,9 @@ void GenericProposalModel::filter(const QString &prefix)
             m_currentItems.append(item);
             if (text.startsWith(prefix)) {
                 // Direct match
-                item->setPrefixMatch(AssistProposalItemInterface::PrefixMatch::Exact);
+                item->setPrefixMatch(text.length() == prefix.length()
+                                     ? AssistProposalItemInterface::PrefixMatch::Full
+                                     : AssistProposalItemInterface::PrefixMatch::Exact);
                 continue;
             }