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str_item and other syntactic elements with Nils are not very usable #5387

vicuna opened this issue Oct 26, 2011 · 2 comments


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commented Oct 26, 2011

Original bug ID: 5387
Reporter: furuse
Assigned to: @diml
Status: closed (set by @xavierleroy on 2013-08-31T10:44:07Z)
Resolution: fixed
Priority: normal
Severity: tweak
Version: 3.12.1
Fixed in version: 3.12.1+dev
Category: -for Camlp4 use

Bug description

<:str_item< let x = 1 >> currently represents the following data structure:

Ast.StSem (_loc,
(Ast.StVal (_loc, Ast.ReNil,
(Ast.BiEq (_loc, (Ast.PaId (_loc, (Ast.IdLid (_loc, "x")))),
(Ast.ExInt (_loc, "1")))))),
(Ast.StNil _loc))

The phrase is not parsed as one str_item but a list of str_items. This makes it impossible to use <:str_item< .. >> as a constructor/pattern for one single str_item.

I do not know what is the best solution, but Jake Donham has seen the same issue and written a nice blog entry. It contains a workaround:


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commented Oct 26, 2011

Comment author: furuse

Some more info. For example, the following pattern

| <:str_item< module $modname$ = struct $sitems$ end >> -> ...

never matches with code like:

module M = struct ... end

Since the former is StSem(.., StNil ..) but the latter lacks StNil.


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commented Jan 5, 2012

Comment author: @diml

Fixed for str_item, sig_item, class_str_item and class_sig_item.

Now Ast.*Nil is not added when the quotation contains only one item.

Commits 11985, 11986, 11987 and 11988.

@vicuna vicuna closed this Aug 31, 2013

@vicuna vicuna added the camlp4 label Mar 14, 2019

@vicuna vicuna added the bug label Mar 20, 2019

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