SemverQuery(
id: "trait_method_const_generic_reordered",
human_readable_name: "trait method const generics were reordered",
description: "A trait method's signature now requires a generic type in the prior spot of a const generic.",
required_update: Major,
lint_level: Deny,
reference_link: Some("https://doc.rust-lang.org/reference/items/generics.html"),
query: r#"
{
CrateDiff {
baseline {
item {
... on Trait {
visibility_limit @filter(op: "=", value: ["$public"])
name @output
importable_path {
path @tag @output
public_api @filter(op: "=", value: ["$true"])
}
method {
public_api_eligible @filter(op: "=", value: ["$true"])
method: name @output @tag
# The method takes the same number of const generic
# and generic type parameters as before.
# Otherwise other lints will trigger instead:
# - `trait_method_requires_different_const_generic_params`
# - `trait_method_requires_different_generic_type_params`
generic_parameter @fold
@transform(op: "count")
@tag(name: "required_const_count")
@output(name: "required_const_count") {
... on GenericConstParameter {
name
}
}
generic_parameter @fold
@transform(op: "count")
@tag(name: "required_type_count")
@output(name: "required_type_count") {
... on GenericTypeParameter {
name
}
}
# But a const generic parameter at a specific position in the signature
# has become a generic type instead. This is a breaking change.
generic_parameter {
... on GenericConstParameter {
const_name: name @output
position @tag @output
}
}
}
}
}
}
current {
item {
... on Trait {
visibility_limit @filter(op: "=", value: ["$public"])
importable_path {
path @filter(op: "=", value: ["%path"])
public_api @filter(op: "=", value: ["$true"])
}
method {
public_api_eligible @filter(op: "=", value: ["$true"])
name @filter(op: "=", value: ["%method"])
generic_parameter @fold
@transform(op: "count")
@filter(op: "=", value: ["%required_const_count"]) {
... on GenericConstParameter {
name
}
}
generic_parameter @fold
@transform(op: "count")
@filter(op: "=", value: ["%required_type_count"]) {
... on GenericTypeParameter {
name
}
}
generic_parameter {
... on GenericTypeParameter {
type_name: name @output
position @filter(op: "=", value: ["%position"])
}
}
span_: span @optional {
filename @output
begin_line @output
end_line @output
}
}
}
}
}
}
}"#,
arguments: {
"public": "public",
"true": true,
},
error_message: "A trait method's signature now requires a generic type parameter where a const generic previously stood. Implementations or calls of this trait method that supplied that const generic will be broken since a generic type is now required instead.",
per_result_error_template: Some("{{name}}::{{method}} used to expect const {{const_name}} in the place of type {{type_name}} in {{span_filename}}:{{span_begin_line}}"),
// TODO: see https://github.com/obi1kenobi/cargo-semver-checks/blob/main/CONTRIBUTING.md#adding-a-witness
// for information about this field.
//
// The witness would be a trait method invocation or implementation using the old
// const generic position, which is insufficient for the new definition.
witness: None,
)