From 4a53b115181a16d681dc05b312bbc913b7f836ac Mon Sep 17 00:00:00 2001
From: lcnr <rust@lcnr.de>
Date: Thu, 8 Jul 2021 22:57:10 +0200
Subject: [PATCH] only check cg defaults wf once instantiated
---
compiler/rustc_typeck/src/check/wfcheck.rs | 26 ++++++++-----------
compiler/rustc_typeck/src/collect.rs | 10 +++++++
.../unused-complex-default-expr.rs | 6 +++++
.../complex-generic-default-expr.full.stderr | 18 -------------
.../complex-generic-default-expr.min.stderr | 2 +-
.../defaults/complex-generic-default-expr.rs | 7 +++--
6 files changed, 31 insertions(+), 38 deletions(-)
create mode 100644 src/test/ui/const-generics/const_evaluatable_checked/unused-complex-default-expr.rs
delete mode 100644 src/test/ui/const-generics/defaults/complex-generic-default-expr.full.stderr
diff --git a/compiler/rustc_typeck/src/check/wfcheck.rs b/compiler/rustc_typeck/src/check/wfcheck.rs
index 0e063c86f2f4e..4838d70a83186 100644
--- a/compiler/rustc_typeck/src/check/wfcheck.rs
+++ b/compiler/rustc_typeck/src/check/wfcheck.rs
@@ -738,15 +738,19 @@ fn check_where_clauses<'tcx, 'fcx>(
}
}
GenericParamDefKind::Const { .. } => {
- // FIXME(const_generics_defaults): Figure out if this
- // is the behavior we want, see the comment further below.
if is_our_default(¶m) {
+ // FIXME(const_generics_defaults): This
+ // is incorrect when dealing with unused substs, for example
+ // for `struct Foo<const N: usize, const M: usize = { 1 - 2 }>`
+ // we should eagerly error.
let default_ct = tcx.const_param_default(param.def_id);
- fcx.register_wf_obligation(
- default_ct.into(),
- tcx.def_span(param.def_id),
- ObligationCauseCode::MiscObligation,
- );
+ if !default_ct.needs_subst() {
+ fcx.register_wf_obligation(
+ default_ct.into(),
+ tcx.def_span(param.def_id),
+ ObligationCauseCode::MiscObligation,
+ );
+ }
}
}
// Doesn't have defaults.
@@ -783,14 +787,6 @@ fn check_where_clauses<'tcx, 'fcx>(
tcx.mk_param_from_def(param)
}
GenericParamDefKind::Const { .. } => {
- // FIXME(const_generics_defaults): I(@lcnr) feel like always
- // using the const parameter is the right choice here, even
- // if it needs substs.
- //
- // Before stabilizing this we probably want to get some tests
- // where this makes a difference and figure out what's the exact
- // behavior we want here.
-
// If the param has a default, ...
if is_our_default(param) {
let default_ct = tcx.const_param_default(param.def_id);
diff --git a/compiler/rustc_typeck/src/collect.rs b/compiler/rustc_typeck/src/collect.rs
index b0e5453b7db92..583ba9392f062 100644
--- a/compiler/rustc_typeck/src/collect.rs
+++ b/compiler/rustc_typeck/src/collect.rs
@@ -2308,6 +2308,16 @@ fn const_evaluatable_predicates_of<'tcx>(
));
}
}
+
+ fn visit_const_param_default(&mut self, _param: HirId, _ct: &'tcx hir::AnonConst) {
+ // Do not look into const param defaults,
+ // these get checked when they are actually instantiated.
+ //
+ // We do not want the following to error:
+ //
+ // struct Foo<const N: usize, const M: usize = { N + 1 }>;
+ // struct Bar<const N: usize>(Foo<N, 3>);
+ }
}
let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
diff --git a/src/test/ui/const-generics/const_evaluatable_checked/unused-complex-default-expr.rs b/src/test/ui/const-generics/const_evaluatable_checked/unused-complex-default-expr.rs
new file mode 100644
index 0000000000000..21f14f58ab5af
--- /dev/null
+++ b/src/test/ui/const-generics/const_evaluatable_checked/unused-complex-default-expr.rs
@@ -0,0 +1,6 @@
+// check-pass
+#![feature(const_generics, const_evaluatable_checked, const_generics_defaults)]
+#![allow(incomplete_features)]
+struct Foo<const N: usize, const M: usize = { N + 1 }>;
+struct Bar<const N: usize>(Foo<N, 3>);
+fn main() {}
diff --git a/src/test/ui/const-generics/defaults/complex-generic-default-expr.full.stderr b/src/test/ui/const-generics/defaults/complex-generic-default-expr.full.stderr
deleted file mode 100644
index e0e2b6c69f280..0000000000000
--- a/src/test/ui/const-generics/defaults/complex-generic-default-expr.full.stderr
+++ /dev/null
@@ -1,18 +0,0 @@
-error: constant expression depends on a generic parameter
- --> $DIR/complex-generic-default-expr.rs:6:34
- |
-LL | struct Foo<const N: usize, const M: usize = { N + 1 }>;
- | ^
- |
- = note: this may fail depending on what value the parameter takes
-
-error: constant expression depends on a generic parameter
- --> $DIR/complex-generic-default-expr.rs:10:21
- |
-LL | struct Bar<T, const TYPE_SIZE: usize = { std::mem::size_of::<T>() }>(T);
- | ^^^^^^^^^
- |
- = note: this may fail depending on what value the parameter takes
-
-error: aborting due to 2 previous errors
-
diff --git a/src/test/ui/const-generics/defaults/complex-generic-default-expr.min.stderr b/src/test/ui/const-generics/defaults/complex-generic-default-expr.min.stderr
index 58abd8db9f09f..44df2ac9f40fa 100644
--- a/src/test/ui/const-generics/defaults/complex-generic-default-expr.min.stderr
+++ b/src/test/ui/const-generics/defaults/complex-generic-default-expr.min.stderr
@@ -1,5 +1,5 @@
error: generic parameters may not be used in const operations
- --> $DIR/complex-generic-default-expr.rs:6:47
+ --> $DIR/complex-generic-default-expr.rs:7:47
|
LL | struct Foo<const N: usize, const M: usize = { N + 1 }>;
| ^ cannot perform const operation using `N`
diff --git a/src/test/ui/const-generics/defaults/complex-generic-default-expr.rs b/src/test/ui/const-generics/defaults/complex-generic-default-expr.rs
index a7b712f7b4b86..d3558007977e4 100644
--- a/src/test/ui/const-generics/defaults/complex-generic-default-expr.rs
+++ b/src/test/ui/const-generics/defaults/complex-generic-default-expr.rs
@@ -1,14 +1,13 @@
// revisions: full min
+//[full] check-pass
#![cfg_attr(full, feature(const_generics))]
#![feature(const_generics_defaults)]
#![allow(incomplete_features)]
struct Foo<const N: usize, const M: usize = { N + 1 }>;
-//[full]~^ ERROR constant expression depends on a generic parameter
-//[min]~^^ ERROR generic parameters may not be used in const operations
+//[min]~^ ERROR generic parameters may not be used in const operations
struct Bar<T, const TYPE_SIZE: usize = { std::mem::size_of::<T>() }>(T);
-//[full]~^ ERROR constant expression depends on a generic parameter
-//[min]~^^ ERROR generic parameters may not be used in const operations
+//[min]~^ ERROR generic parameters may not be used in const operations
fn main() {}