For a clock (ck on x) to be well-formed in an environment H, we must
have H x = ck, i.e., the clock of x is the same as the clock ck of the
stream being sampled.
This constraint is guaranteed by construction for fully inferred clocks
(by the rules for when and merge), but nothing guarantees that user
declarations be well-formed. This can lead to problems.
For instance, this invalid program is incorrectly accepted:
node f (x : bool; a : bool :: . on b;
b : bool :: . on a) returns (y:bool);
let
y = true;
tel
as is this one:
node f(a: bool :: . on a; b: bool :: . on a)
returns (z: bool);
var w : bool;
let
w = a when b;
z = false fby w;
tel
This invalid program is incorrectly accepted and leads to an internal
compiler error:
node f (x : bool) returns (y:bool);
var a : bool :: . on b;
b : bool :: . on a;
let
y = true;
a = true;
b = true;
tel
This patch enforces the well-formedness constraint. It gives a sensible
error message when the constraint cannot be satisfied.
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