nameHint is unreliable due to foldr/build fusion

[bgamari]

If one writes nameHint (SSym @"hi") ... there is a good chance that GHC's unpack rewrite rule will rewrite the String in the term-level evidence carried by SSym (which is the only thing preserved in the netlist) into build (unpackFoldrCString# "hi"). The logic in Clash.Netlist.BlackBox.Util.exprToString understandably cannot deal with this, resulting in errors of the form:

    Clash error call:
    Clash.Netlist.BlackBox.Util(761): Error when reducing to string in ~NAME construct: Clash.Netlist.BlackBox.Util(937): Could not extract string from BlackBoxE "Clash.Promoted.Symbol.SSymbol" [] [] [] (BBTemplate [Lit 0]) (Context {bbName = "Clash.Promoted.Symbol.SSymbol", bbResults = [(Identifier (RawIdentifier "v" Nothing []) Nothing,String)], bbInputs = [(BlackBoxE "GHC.CString.unpackFoldrCString#" [] [] [] (BBTemplate [Lit 0]) (Context {bbName = "GHC.CString.unpackFoldrCString#", bbResults = [(Identifier (RawIdentifier "v" Nothing []) Nothing,String)], bbInputs = [(Literal Nothing (StringLit "mealyState"),String,True),(Identifier (RawIdentifier "Clash.Normalize.Primitives.removedArg" Nothing []) Nothing,Void Nothing,False),(BlackBoxE "Clash.Normalize.Primitives.removedArg" [] [] [] (BBTemplate [Err Nothing]) (Context {bbName = "Clash.Normalize.Primitives.removedArg", bbResults = [(Identifier (RawIdentifier "v" Nothing []) Nothing,String)], bbInputs = [], bbFunctions = fromList [], bbQsysIncName = [], bbLevel = 0, bbCompName = RawIdentifier "clk_manager" (Just (UniqueIdentifier {i_baseName = "clk_manager", i_baseNameCaseFold = "clk_manager", i_extensionsRev = [], i_idType = Basic, i_hdl = Verilog, i_provenance = []})) [], bbCtxName = Just "$s$fHasEntityPortsFUN_$centityPortRep_$s$w$centityPortRep11_$s$fHasEntityPortsFUN_$centityPortRep_$s$w$centityPortRep10_$s$fHasEntityPortsFUN_$centityPortRep_$s$w$centityPortRep9_$s$fHasEntityPortsFUN_$centityPortRep_$s$w$centityPortRep1_$s$fHasEntityPortsFUN_$centityPortRep_$s$w$centityPortRep_build_v"}) True,String,True)], bbFunctions = fromList [(1,[(Right (RawIdentifier "" Nothing [],[Assignment (RawIdentifier "~RESULT" Nothing []) Cont (Identifier (RawIdentifier "~ERRORO" Nothing []) Nothing)]),Cont,[],[],[],Context {bbName = "Clash.Normalize.Primitives.removedArg", bbResults = [(Identifier (RawIdentifier "v" Nothing []) Nothing,String)], bbInputs = [], bbFunctions = fromList [], bbQsysIncName = [], bbLevel = 1, bbCompName = RawIdentifier "clk_manager" (Just (UniqueIdentifier {i_baseName = "clk_manager", i_baseNameCaseFold = "clk_manager", i_extensionsRev = [], i_idType = Basic, i_hdl = Verilog, i_provenance = []})) [], bbCtxName = Just "$s$fHasEntityPortsFUN_$centityPortRep_$s$w$centityPortRep11_$s$fHasEntityPortsFUN_$centityPortRep_$s$w$centityPortRep10_$s$fHasEntityPortsFUN_$centityPortRep_$s$w$centityPortRep9_$s$fHasEntityPortsFUN_$centityPortRep_$s$w$centityPortRep1_$s$fHasEntityPortsFUN_$centityPortRep_$s$w$centityPortRep_build_v"})])], bbQsysIncName = [], bbLevel = 0, bbCompName = RawIdentifier "clk_manager" (Just (UniqueIdentifier {i_baseName = "clk_manager", i_baseNameCaseFold = "clk_manager", i_extensionsRev = [], i_idType = Basic, i_hdl = Verilog, i_provenance = []})) [], bbCtxName = Just "$s$fHasEntityPortsFUN_$centityPortRep_$s$w$centityPortRep11_$s$fHasEntityPortsFUN_$centityPortRep_$s$w$centityPortRep10_$s$fHasEntityPortsFUN_$centityPortRep_$s$w$centityPortRep9_$s$fHasEntityPortsFUN_$centityPortRep_$s$w$centityPortRep1_$s$fHasEntityPortsFUN_$centityPortRep_$s$w$centityPortRep_build_v"}) True,String,True)], bbFunctions = fromList [], bbQsysIncName = [], bbLevel = 0, bbCompName = RawIdentifier "clk_manager" (Just (UniqueIdentifier {i_baseName = "clk_manager", i_baseNameCaseFold = "clk_manager", i_extensionsRev = [], i_idType = Basic, i_hdl = Verilog, i_provenance = []})) [], bbCtxName = Just "$s$fHasEntityPortsFUN_$centityPortRep_$s$w$centityPortRep11_$s$fHasEntityPortsFUN_$centityPortRep_$s$w$centityPortRep10_$s$fHasEntityPortsFUN_$centityPortRep_$s$w$centityPortRep9_$s$fHasEntityPortsFUN_$centityPortRep_$s$w$centityPortRep1_$s$fHasEntityPortsFUN_$centityPortRep_$s$w$centityPortRep_v"}) True referred to by Lit 0

Perplexingly, the build call doesn't seem to be reflected in the netlist.