CppTools: More consistent fuzzy matching behavior

There were annoying inconsistencies, for instance:
    - A not fully matching declaration was found from the definition,
      but not vice versa.
    - An implementation MyClass::foo(int) would fall back to a
      declaration foo(), but an implementation MyClass::foo() would
      not fall back to a declaration foo(int).
These cases behave consistently now. To this end, the clang code model
now forwards to the built-in code model if a function lookup has failed.

Fuzzy matching for free functions has been limited, as the cons appear
to outweigh the pros. For instance:
    void foo(int);
    void foo(double) {}
Following the definition would lead to the non-matching declaration,
which the user most likely does not want.

As a side effect, redundant code has been removed in the SymbolFinder
class.

Fixes: QTCREATORBUG-20279
Change-Id: Ib97d6710c7e12fb0fdbc30b51a0067e09bfc2190
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

1 files changed, 72 insertions, 4 deletions

diff --git a/src/plugins/cppeditor/followsymbol_switchmethoddecldef_test.cpp b/src/plugins/cppeditor/followsymbol_switchmethoddecldef_test.cpp
index 8bbb010422..7532b77e8d 100644
--- a/src/plugins/cppeditor/followsymbol_switchmethoddecldef_test.cpp
+++ b/src/plugins/cppeditor/followsymbol_switchmethoddecldef_test.cpp
@@ -935,6 +935,16 @@ void CppEditorPlugin::test_FollowSymbolUnderCursor_data()
         "void Foo::foo(int) {}\n"
     );
 
+    QTest::newRow("matchFunctionSignature_Follow_3.5") << _(
+        "void foo(int);\n"
+        "void @$foo() {}\n"
+    );
+
+    QTest::newRow("matchFunctionSignature_Follow_3.6") << _(
+        "void foo(int);\n"
+        "void @$foo(double) {}\n"
+    );
+
     QTest::newRow("matchFunctionSignature_Follow_4") << _(
         "class Foo {\n"
         "    void foo(int);\n"
@@ -963,17 +973,33 @@ void CppEditorPlugin::test_FollowSymbolUnderCursor_data()
         "void Foo::@foo(int) {}\n"
     );
 
-    QTest::newRow("matchFunctionSignature_Follow_8") << _(
+    QTest::newRow("matchFunctionSignature_Follow_8_fuzzy") << _(
         "class Foo {\n"
-        "    void @$foo(int *);\n"
+        "    void @foo(int *);\n"
+        "};\n"
+        "void Foo::$foo(const int *) {}\n"
+    );
+
+    QTest::newRow("matchFunctionSignature_Follow_8_exact") << _(
+        "class Foo {\n"
+        "    void @foo(int *);\n"
         "};\n"
         "void Foo::foo(const int *) {}\n"
+        "void Foo::$foo(int *) {}\n"
     );
 
-    QTest::newRow("matchFunctionSignature_Follow_9") << _(
+    QTest::newRow("matchFunctionSignature_Follow_9_fuzzy") << _(
         "class Foo {\n"
-        "    void @$foo(int&);\n"
+        "    void @foo(int&);\n"
         "};\n"
+        "void Foo::$foo(const int&) {}\n"
+    );
+
+    QTest::newRow("matchFunctionSignature_Follow_9_exact") << _(
+        "class Foo {\n"
+        "    void @foo(int&);\n"
+        "};\n"
+        "void Foo::$foo(int&) {}\n"
         "void Foo::foo(const int&) {}\n"
     );
 
@@ -1171,6 +1197,48 @@ void CppEditorPlugin::test_FollowSymbolUnderCursor_multipleDocuments_data()
                                 "foo.cpp")
     );
 
+    QTest::newRow("matchFunctionSignatureFuzzy1Forward") << (QList<TestDocumentPtr>()
+        << TestDocument::create("class Foo {\n"
+                                "    void @foo(int);\n"
+                                "    void foo();\n"
+                                "};\n",
+                                "foo.h")
+        << TestDocument::create("#include \"foo.h\"\n"
+                                "void Foo::$foo() {}\n",
+                                "foo.cpp")
+    );
+
+    QTest::newRow("matchFunctionSignatureFuzzy1Backward") << (QList<TestDocumentPtr>()
+        << TestDocument::create("class Foo {\n"
+                                "    void $foo(int);\n"
+                                "};\n",
+                                "foo.h")
+        << TestDocument::create("#include \"foo.h\"\n"
+                                "void Foo::@foo() {}\n",
+                                "foo.cpp")
+    );
+
+    QTest::newRow("matchFunctionSignatureFuzzy2Forward") << (QList<TestDocumentPtr>()
+        << TestDocument::create("class Foo {\n"
+                                "    void foo(int);\n"
+                                "    void @foo();\n"
+                                "};\n",
+                                "foo.h")
+        << TestDocument::create("#include \"foo.h\"\n"
+                                "void Foo::$foo(int) {}\n",
+                                "foo.cpp")
+    );
+
+    QTest::newRow("matchFunctionSignatureFuzzy2Backward") << (QList<TestDocumentPtr>()
+        << TestDocument::create("class Foo {\n"
+                                "    void $foo();\n"
+                                "};\n",
+                                "foo.h")
+        << TestDocument::create("#include \"foo.h\"\n"
+                                "void Foo::@foo(int) {}\n",
+                                "foo.cpp")
+    );
+
     QTest::newRow("globalVar") << QList<TestDocumentPtr>{
             TestDocument::create("namespace NS { extern int @globalVar; }\n", "file.h"),
             TestDocument::create(