loplugin:unnecessaryparen: signed numeric literals

Change-Id: I75c8224452ca9c3711a2ccaca9ecf549fa59cb64
Reviewed-on: https://gerrit.libreoffice.org/45549
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

2 files changed, 22 insertions, 0 deletions

diff --git a/compilerplugins/clang/test/unnecessaryparen.cxx b/compilerplugins/clang/test/unnecessaryparen.cxx
index 78e2096abf9e..b7117a126edb 100644
--- a/compilerplugins/clang/test/unnecessaryparen.cxx
+++ b/compilerplugins/clang/test/unnecessaryparen.cxx
@@ -82,6 +82,15 @@ int main()
     // Expecting just one error, not reported twice during TraverseInitListExpr:
     int a[] = {(x)}; // expected-error {{unnecessary parentheses around identifier [loplugin:unnecessaryparen]}}
     (void) a;
+
+    (void) (+1); // expected-error {{unnecessary parentheses around signed numeric literal [loplugin:unnecessaryparen]}}
+    (void) (-1); // expected-error {{unnecessary parentheses around signed numeric literal [loplugin:unnecessaryparen]}}
+
+    // For simplicity's sake, even warn about pathological cases that would require adding
+    // whitespace when removing the parentheses (as is also necessary in other cases anyway, like
+    // "throw(x);"); it is unlikely that there are any actual occurrences of code like "-(-1)" that
+    // would benefit from the parentheses readability-wise, compared to "- -1":
+    (void) -(-1); // expected-error {{unnecessary parentheses around signed numeric literal [loplugin:unnecessaryparen]}}
 };
 
 struct S2 {
diff --git a/compilerplugins/clang/unnecessaryparen.cxx b/compilerplugins/clang/unnecessaryparen.cxx
index 692e23706cc9..db241024dba4 100644
--- a/compilerplugins/clang/unnecessaryparen.cxx
+++ b/compilerplugins/clang/unnecessaryparen.cxx
@@ -180,6 +180,19 @@ bool UnnecessaryParen::VisitParenExpr(const ParenExpr* parenExpr)
                 << parenExpr->getSourceRange();
             handled_.insert(parenExpr);
         }
+    } else if (auto const e = dyn_cast<UnaryOperator>(subExpr)) {
+        auto const op = e->getOpcode();
+        if (op == UO_Plus || op == UO_Minus) {
+            auto const e2 = e->getSubExpr();
+            if (isa<IntegerLiteral>(e2) || isa<FloatingLiteral>(e2) || isa<ImaginaryLiteral>(e2)) {
+                report(
+                    DiagnosticsEngine::Warning,
+                    "unnecessary parentheses around signed numeric literal",
+                    parenExpr->getLocStart())
+                    << parenExpr->getSourceRange();
+                handled_.insert(parenExpr);
+            }
+        }
     } else if (isa<CXXNamedCastExpr>(subExpr)) {
         report(
             DiagnosticsEngine::Warning, "unnecessary parentheses around cast",