rule: inferable-type-not-used #194
Description
Description
When a value is assigned, returned, or otherwise has a RLS with a static type, disallow re-specifying that type. This mostly means changing struct literals to anonymous struct literals, removing redundant @as, or using a decl literal over a namespace.
Motivating example:
pub fn fstat(_: *NodeFS, args: Arguments.Fstat, _: Flavor) Maybe(Return.Fstat) {
return switch (Syscall.fstat(args.fd)) {
.result => |result| .{ .result = Stats.init(result, false) },
- .err => |err| Maybe(Return.Fstat){ .err = err },
+ .err => |err| .{ .err = err },
};
}Examples
Examples of incorrect code for this rule
const x: u32 = @as(u32, @intCast(y)); // remove as expression
pub fn f1(a: u64) u32 {
return @as(u32, @intCast(a)); // remove as expression
}
const T = struct {
field: u32,
const x: T = .{ .field = 2 };
};
pub fn hello(a: T) void {
_ = a;
}
const Enum = enum { a };
const z: Enum = z: {
hello(T{ // remove `T`
.field = @as(u32, @intCast(y)), // remove as expression
});
hello(T.x); // Remove `T`
break :z Enum.z; // remove `Enum`
};
fn other(comptime hello: type, n: u64) SomeComplex(hello) {
return SomeComplex(hello).init(n);
// use decl literal `.init(n)`
// can realize that the literal text `SomeComplex(hello)` is re-used
}Examples that would not be flagged.
const x = @as(u32, @intCast(y)); // destination has no type
pub fn goodbye(a: anytype) void {
_ = a;
}
comptime {
goodbye(T{ // cannot remove T as argument is `anytype`
.field = @as(u32, @intCast(y)), // `.field` has no type
});
}
fn other(n: u64) u32 {
// when the types are not the same, it should not apply.
// the extra coercion does something
return @as(u16, @truncate(n));
}