[Ada] Casing on composite values
Pierre-Marie de Rodat
Thu Jun 17 14:33:11 GMT 2021
Initial support for casing on composite values if extensions are allowed
(e.g., if -gnatX is specified). The implementation is far from complete.
Tested on x86_64-pc-linux-gnu, committed on trunk
(Expand_N_Case_Statement): If extensions are allowed and the
case selector is not of a discrete type, then call
Expand_General_Case_Statement to generate expansion instead of
flagging the non-discrete selector as an error.
* sem_case.ads (Is_Case_Choice_Pattern): New Boolean-valued
function for testing whether a given expression occurs as part
of a case choice pattern.
* sem_case.adb (Composite_Case_Ops): New package providing
support routines for the new form of case statements. This
includes a nested package, Composite_Case_Ops.Value_Sets, which
encapsulates the "representative values" implementation of
composite value sets.
(Check_Choices.Check_Case_Pattern_Choices): New procedure for
semantic checking of non-discrete case choices. This includes
the checks pertaining to coverage and overlapping.
(Check_Choices.Check_Composite_Case_Selector): New procedure for
semantic checking of non-discrete case selectors.
(Check_Choices): If extensions are allowed then a non-discrete
selector type no longer implies that an error must have been
flagged earlier. Instead of simply returning, call
Check_Composite_Case_Selector and Check_Case_Pattern_Choices.
(Is_Case_Choice_Pattern): Body of new function declared in
* sem_ch5.adb (Analyze_Case_Statement): If extensions are
allowed, then we can't use RM 5.4's "The selecting_expression is
expected to be of any discrete type" name resolution rule.
Handle the case where the type of the selecting expression is
not discrete, as well as the new ambiguous-name-resolution error
cases made possible by this change.
* sem_res.adb (Resolve_Entity_Name): It is ok to treat the name
of a type or subtype as an expression if it is part of a case
choice pattern, as in "(Field1 => Positive, Field2 => <>)".
* exp_aggr.adb (Expand_Record_Aggregate): Do not expand case
* gen_il-fields.ads: Define two new node attributes,
Binding_Chars and Multidefined_Bindings.
* gen_il-gen-gen_nodes.adb: The new Multidefined_Bindings
attribute is Boolean-valued and may be set on
N_Case_Statement_Alternative nodes. The new Binding_Chars
attribute is Name_Id-valued and may be set on
* par-ch4.adb (P_Record_Or_Array_Component_Association): When
parsing a component association, check for both new syntax forms
used to specify a bound value in a case-choice aggregate. In
the case of a box value, an identifier may occur within the box,
as in "Foo => <Abc>" instead of "Foo => <>". In the more general
case, an expression (or a box) may be followed by "is
<identifier>", as in
"Foo => Bar is Abc" instead of just "Foo => Bar".
* sem_aggr.adb (Resolve_Record_Aggregate): Do not transform box
component values in a case-choice aggregate.
* sinfo.ads: Provide comments for the new attributes added in
* doc/gnat_rm/implementation_defined_pragmas.rst: Describe this
new feature in documentation for pragma Extensions_Allowed.
* gnat_rm.texi: Regenerate.
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