Avoid loplugin:stringviewparam when there already is a string_view overload

This avoids clang-cl

> In file included from core/connectivity/source/drivers/ado/Aolevariant.cxx:20:
> connectivity/source/inc\ado/Aolevariant.hxx(72,40): error: replace function parameter of type 'const rtl::OUString &' with 'std::u16string_view' [loplugin:stringviewparam]
>             OLEVariant(const OUString& us)
>                        ~~~~~~~~~~~~~~~~^~

which would make that OLEVariant ctor overload redundant with the existing

OLEVariant(std::u16string_view us);

overload, but with the OUString overload gone, implicit conversions from
OUString to OLEVariant would no longer work, e.g.,

> connectivity/source/drivers/ado/AColumn.cxx(184,76): error: no viable conversion from 'rtl::OUString' to 'const connectivity::ado::OLEVariant'
>             OTools::putValue(m_aColumn.get_Properties(), sAdoPropertyName, getString(rValue));
>                                                                            ^~~~~~~~~~~~~~~~~

Change-Id: I92a5cc29d9fd2a5ff1a951f79df64879d0f71743
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/109180
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

2 files changed, 67 insertions, 0 deletions

diff --git a/compilerplugins/clang/stringviewparam.cxx b/compilerplugins/clang/stringviewparam.cxx
index a96d8cad4929..86ee7c21b393 100644
--- a/compilerplugins/clang/stringviewparam.cxx
+++ b/compilerplugins/clang/stringviewparam.cxx
@@ -206,6 +206,57 @@ SmallVector<DeclRefExpr const*, 2> relevantCXXOperatorCallExpr(CXXOperatorCallEx
     return {};
 }
 
+//TODO: current implementation is not at all general, just tests what we encounter in practice:
+bool hasStringViewOverload(ParmVarDecl const* decl)
+{
+    auto const d1 = cast<FunctionDecl>(decl->getDeclContext());
+    auto const ctx = d1->getDeclContext();
+    if (!ctx->isLookupContext())
+    {
+        return false;
+    }
+    auto const res = ctx->lookup(d1->getDeclName());
+    auto const idx = decl->getFunctionScopeIndex();
+    auto const n = d1->getNumParams();
+    assert(n > idx);
+    for (auto i = res.begin(); i != res.end(); ++i)
+    {
+        auto const d2 = dyn_cast<FunctionDecl>(*i);
+        if (d2 == nullptr)
+        {
+            continue;
+        }
+        if (d2->getNumParams() != n)
+        {
+            continue;
+        }
+        auto match = true;
+        for (unsigned j = 0; j != n; ++j)
+        {
+            if (j == idx)
+            {
+                //TODO: check for exactly std::string_view or std::u16string_view:
+                if (!isStringView(d2->getParamDecl(j)->getType()))
+                {
+                    match = false;
+                    break;
+                }
+            }
+            else if (d1->getParamDecl(j)->getType().getCanonicalType()
+                     != d2->getParamDecl(j)->getType().getCanonicalType())
+            {
+                match = false;
+                break;
+            }
+        }
+        if (match)
+        {
+            return true;
+        }
+    }
+    return false;
+}
+
 class StringViewParam final
     : public loplugin::FunctionAddress<loplugin::FilteringPlugin<StringViewParam>>
 {
@@ -439,6 +490,10 @@ private:
             {
                 continue;
             }
+            if (hasStringViewOverload(i))
+            {
+                continue;
+            }
             auto const t = relevantStringType(i->getType().getNonReferenceType());
             assert(t != StringType::None);
             report(DiagnosticsEngine::Warning,
diff --git a/compilerplugins/clang/test/stringviewparam.cxx b/compilerplugins/clang/test/stringviewparam.cxx
index 56fadbea71cf..24dab18e0f9c 100644
--- a/compilerplugins/clang/test/stringviewparam.cxx
+++ b/compilerplugins/clang/test/stringviewparam.cxx
@@ -71,4 +71,16 @@ struct Converter
     }
 };
 
+void f9(std::u16string_view);
+void f9(OUString const& s) { return f9(std::u16string_view(s)); }
+
+struct S10
+{
+    S10(std::u16string_view);
+    S10(OUString const& s)
+        : S10(std::u16string_view(s))
+    {
+    }
+};
+
 /* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */