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checker: disallow structs with @[params] attribute as mutable function parameters #21206

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merged 9 commits into from
May 4, 2024
Merged

checker: disallow structs with @[params] attribute as mutable function parameters #21206

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87e877f
fix
ttytm Apr 6, 2024
28a7e51
test
ttytm Apr 6, 2024
67be7e6
Revert "test"
ttytm Apr 25, 2024
458c836
Revert "fix"
ttytm Apr 25, 2024
b73c8d7
disallow mut params struct in fn_decl
ttytm Apr 25, 2024
bc6830c
add error test
ttytm Apr 25, 2024
22300ee
remove test that used mut params struct as regular struct
ttytm Apr 25, 2024
e50ec29
make sure there is a test that tests mutable struct parameter
ttytm Apr 25, 2024
8ecdda2
rm eventually unused
ttytm Apr 25, 2024
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11 changes: 9 additions & 2 deletions vlib/v/checker/fn.v
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Original file line number Diff line number Diff line change
Expand Up @@ -254,6 +254,10 @@ fn (mut c Checker) fn_decl(mut node ast.FnDecl) {
c.error('generic struct `${pure_sym_name}` in fn declaration must specify the generic type names, e.g. ${pure_sym_name}[T]',
param.type_pos)
}
if param.is_mut && arg_typ_sym.info.attrs.any(it.name == 'params') {
c.error('declaring a mutable parameter that accepts a struct with the `@[params]` attribute is not allowed',
param.type_pos)
}
} else if arg_typ_sym.info is ast.Interface {
if arg_typ_sym.info.generic_types.len > 0 && !param.typ.has_flag(.generic)
&& arg_typ_sym.info.concrete_types.len == 0 {
Expand Down Expand Up @@ -1278,8 +1282,11 @@ fn (mut c Checker) fn_call(mut node ast.CallExpr, mut continue_check &bool) ast.
} else {
if param.is_mut {
tok := param.specifier()
c.error('function `${node.name}` parameter `${param.name}` is `${tok}`, so use `${tok} ${call_arg.expr}` instead',
call_arg.expr.pos())
param_sym := c.table.sym(param.typ)
if !(param_sym.info is ast.Struct && param_sym.info.attrs.any(it.name == 'params')) {
c.error('function `${node.name}` parameter `${param.name}` is `${tok}`, so use `${tok} ${call_arg.expr}` instead',
call_arg.expr.pos())
}
} else {
c.fail_if_unreadable(call_arg.expr, arg_typ, 'argument')
}
Expand Down
7 changes: 7 additions & 0 deletions vlib/v/checker/tests/mut_parms_struct_param_err.out
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@@ -0,0 +1,7 @@
vlib/v/checker/tests/mut_parms_struct_param_err.vv:8:17: error: declaring a mutable parameter that accepts a struct with the `@[params]` attribute is not allowed
6 | }
7 |
8 | fn foo(mut opts Params) bool {
| ~~~~~~
9 | return opts.a
10 | }
12 changes: 12 additions & 0 deletions vlib/v/checker/tests/mut_parms_struct_param_err.vv
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Original file line number Diff line number Diff line change
@@ -0,0 +1,12 @@
@[params]
struct Params {
mut:
a bool
x int
}

fn foo(mut opts Params) bool {
return opts.a
}

foo(a: true)
24 changes: 10 additions & 14 deletions vlib/v/tests/struct_test.v
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Expand Up @@ -25,7 +25,8 @@ struct Lol {

struct User {
name string
age int
mut:
age int
}

struct Foo {
Expand Down Expand Up @@ -257,14 +258,12 @@ fn bar_config(c Config, def int) {
assert c.def == def
}

fn mut_bar_config(mut c Config, def int) &Config {
c.n = c.def
assert c.n == def
return unsafe { c }
}

fn foo_user(u User) {}

fn foo_mut_user(mut u User) {
u.age++
}

fn test_struct_literal_args() {
foo_config(20,
n: 10
Expand All @@ -277,17 +276,14 @@ fn test_struct_literal_args() {
bar_config(Config{}, 10)
bar_config(Config{ def: 4 }, 4)

mut c_ := Config{
def: 10
}
c := mut_bar_config(mut c_, 10)
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This should remain to be allowed, the call has mut c_.

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The inconsistency, is only when you use the default f(), and f gets a mutable parameter, that was created implicitly. If you pass it explicitly, you and the reader will know where it originated.

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The inconsistency, is only when you use the default f(), and f gets a mutable parameter, that was created implicitly. If you pass it explicitly, you and the reader will know where it originated.

The test used Config (a struct with a @[params] attribute) to test passing mutable structs. That's why I added another test passing a mut struct that isn't a params struct.

Else wouldn't this disagree with alex, disallowing mut params, and lead us where I wanted to go in the second comment? Allowing a params struct like this:

mut p := Params{a: true}
foo(mut p)

Or is what is meant to be done here to only disallow trailing mut params structs?

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I do not know. @medvednikov what do you think?

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@[params]
struct Config {}

It's a params struct, so it makes sense that the new mut rule is applied to it as well.

It's fine.

Thanks, great job.

assert c.n == 10
assert c.def == 10

foo_user(name: 'Peter')
foo_user(name: 'Peter')
foo_user(age: 7)
foo_user(name: 'Stew', age: 50)

mut user := User{'Stew', 50}
foo_mut_user(mut user)
assert user.age == 51
}

struct City {
Expand Down