This PR should be the base for discussion, do not merge it yet!

It correctly detects reg/wire mix and incorrect use on blocking,nonblocking assignments within blocks and assign statements.

What it DOES'T do:
Detect registers connected to output ports of instances.

Where it FAILS:
memorty nonblocking assignments causes spurious (I assume??) errors on yosys-generated "_ADDR", "_DATA", "EN" signals.

You can test it with tests/simple/reg_wire_error.v (look inside for the comments to enable/disable specific lines)

tests/simple/reg_wire_error.v

@@ -0,0 +1,40 @@
+module sub_mod(input i_in, output o_out);
+assign o_out = i_in;
+endmodule
+
+module test(i_clk, i_reg, o_reg, o_wire);
+input i_clk;
+input i_reg;
+output o_reg;
+output o_wire;
+
+// Enable this to see how it doesn't fail on yosys although it should
+//reg o_wire;
+// Enable this instead of the above to see how logic can be mapped to a wire
+logic o_wire;
+// Enable this to see how it doesn't fail on yosys although it should
+//reg i_reg;
+// Disable this to see how it doesn't fail on yosys although it should
+reg o_reg;
+
+logic l_reg;
+
+// Enable this to tst if logic-turne-reg will catch assignments even if done before it turned into a reg
+//assign l_reg = !o_reg;
+initial o_reg = 1'b0;
+always @(posedge i_clk)
+begin
+  o_reg <= !o_reg;
+  l_reg <= !o_reg;
+end
+
+assign o_wire = !o_reg;
+// Uncomment this to see how a logic already turned intoa reg can be freely assigned on yosys
+//assign l_reg = !o_reg;
+
+sub_mod sm_inst (
+  .i_in(1'b1),
+  .o_out(o_reg)
+);
+endmodule
+