[m-dev.] Re: diff: check for unbound type vars in class constraints

[Fergus Henderson]

On 16-Aug-2000, Fergus Henderson <fjh at cs.mu.oz.au> wrote:
> 
> Check for various cases of type variables that occur only in type class
> constraints.  These cases are all errors, since the type variable can
> never be bound, but previously the compiler was not checking for these
> errors.
...
> compiler/make_hlds.m:
> 	Check that type vars in constraints on pred and func declarations
> 	(including type class methods) occur in the procedure's argument types.
> 	This enforces the following requirement from the "type class
> 	constraints on predicates and functions" section of the Mercury
> 	language reference manual:
> 	 | where ... TYPEVARIABLE is a type variable that appears in the
> 	 | predicate's or function's type signature.

I forgot to see if that change would affect any of the other .err_exp
files in tests/invalid.  It turns out that I need to make the following
additional change.

----------

tests/invalid/typeclass_test_9.err_exp:
	Update the expected output for this change to reflect
	the additional errors output as a result of my recent change.
	The change in question was the one compiler/make_hlds.m to
	make it report errors for type variables in constraints
	that do not occur in the procedure's argument types.

Index: typeclass_test_9.err_exp
===================================================================
RCS file: /home/mercury1/repository/tests/invalid/typeclass_test_9.err_exp,v
retrieving revision 1.1
diff -u -d -u -r1.1 typeclass_test_9.err_exp
--- typeclass_test_9.err_exp	1999/02/12 04:19:31	1.1
+++ typeclass_test_9.err_exp	2000/08/16 09:08:54
@@ -2,6 +2,14 @@
 typeclass_test_9.m:001:   warning: module `std_util'
 typeclass_test_9.m:001:   is imported in the interface, but is not
 typeclass_test_9.m:001:   used in the interface.
+typeclass_test_9.m:004: In declaration for predicate `typeclass_test_9:p/0':
+typeclass_test_9.m:004:   error in type class constraints: type variable
+typeclass_test_9.m:004:   `T' occurs only in the constraints,
+typeclass_test_9.m:004:   not in the predicate's argument types.
+typeclass_test_9.m:006: In declaration for predicate `typeclass_test_9:q/0':
+typeclass_test_9.m:006:   error in type class constraints: type variable
+typeclass_test_9.m:006:   `T' occurs only in the constraints,
+typeclass_test_9.m:006:   not in the predicate's argument types.
 typeclass_test_9.m:010: Error: multiply defined (or overlapping) instance
 typeclass_test_9.m:010: declarations for class `typeclass_test_9:foo/1'.
 typeclass_test_9.m:007: Previous instance declaration was here.

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh>  |  of excellence is a lethal habit"
PGP: finger fjh at 128.250.37.3        |     -- the last words of T. S. Garp.
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