Fix to exclude strings from toggle coverage (#2766) (#2767)

src/V3AstNodes.h

@@ -2170,7 +2170,7 @@ public:
         return ((isIO() || isSignal())
                 && (isIO() || isBitLogic())
                 // Wrapper would otherwise duplicate wrapped module's coverage
-                && !isSc() && !isPrimaryIO() && !isConst() && !isDouble());
+                && !isSc() && !isPrimaryIO() && !isConst() && !isDouble() && !isString());
     }
     bool isClassMember() const { return varType() == AstVarType::MEMBER; }
     bool isStatementTemp() const { return (varType() == AstVarType::STMTTEMP); }

test_regress/t/t_cover_toggle.v

@@ -7,11 +7,13 @@
 module t (/*AUTOARG*/
    // Inputs
    clk,
-   check_real
+   check_real,
+   check_string
    );
 
    input clk;
    input real check_real; // Check issue #2741
+   input string check_string; // Check issue #2766
 
    typedef struct packed {
       union packed {