From 79dc9a76a6272dc2e080237de27406b1456d7c2c Mon Sep 17 00:00:00 2001 From: Fabian Wolff Date: Fri, 11 Jun 2021 20:12:40 +0200 Subject: [PATCH] Suggest a FnPtr type if a FnDef type is found --- compiler/rustc_typeck/src/collect/type_of.rs | 51 +++++++++++++++---- src/test/ui/suggestions/unnamable-types.rs | 14 +++-- .../ui/suggestions/unnamable-types.stderr | 48 ++++++++--------- 3 files changed, 74 insertions(+), 39 deletions(-) diff --git a/compiler/rustc_typeck/src/collect/type_of.rs b/compiler/rustc_typeck/src/collect/type_of.rs index 38678cc76e0d..abe5d69a3b3c 100644 --- a/compiler/rustc_typeck/src/collect/type_of.rs +++ b/compiler/rustc_typeck/src/collect/type_of.rs @@ -9,7 +9,7 @@ use rustc_hir::{HirId, Node}; use rustc_middle::hir::map::Map; use rustc_middle::ty::subst::{GenericArgKind, InternalSubsts}; use rustc_middle::ty::util::IntTypeExt; -use rustc_middle::ty::{self, DefIdTree, Ty, TyCtxt, TypeFoldable}; +use rustc_middle::ty::{self, DefIdTree, Ty, TyCtxt, TypeFoldable, TypeFolder}; use rustc_span::symbol::Ident; use rustc_span::{Span, DUMMY_SP}; @@ -749,15 +749,38 @@ fn infer_placeholder_type( span: Span, item_ident: Ident, ) -> Ty<'_> { - fn contains_anonymous(ty: Ty<'_>) -> bool { - for gen_arg in ty.walk() { - if let ty::subst::GenericArgKind::Type(inner_ty) = gen_arg.unpack() { - if let ty::FnDef(..) | ty::Closure(..) | ty::Generator(..) = inner_ty.kind() { - return true; + // Attempts to make the type nameable by turning FnDefs into FnPtrs. + struct MakeNameable<'tcx> { + success: bool, + tcx: TyCtxt<'tcx>, + } + + impl<'tcx> MakeNameable<'tcx> { + fn new(tcx: TyCtxt<'tcx>) -> Self { + MakeNameable { success: true, tcx } + } + } + + impl TypeFolder<'tcx> for MakeNameable<'tcx> { + fn tcx(&self) -> TyCtxt<'tcx> { + self.tcx + } + + fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> { + if !self.success { + return ty; + } + + match ty.kind() { + ty::FnDef(def_id, _) => self.tcx.mk_fn_ptr(self.tcx.fn_sig(*def_id)), + // FIXME: non-capturing closures should also suggest a function pointer + ty::Closure(..) | ty::Generator(..) => { + self.success = false; + ty } + _ => ty.super_fold_with(self), } } - false } let ty = tcx.diagnostic_only_typeck(def_id).node_type(body_id.hir_id); @@ -773,11 +796,14 @@ fn infer_placeholder_type( err.suggestions.clear(); // Suggesting unnameable types won't help. - if !contains_anonymous(ty) { + let mut mk_nameable = MakeNameable::new(tcx); + let ty = mk_nameable.fold_ty(ty); + let sugg_ty = if mk_nameable.success { Some(ty) } else { None }; + if let Some(sugg_ty) = sugg_ty { err.span_suggestion( span, "provide a type for the item", - format!("{}: {}", item_ident, ty), + format!("{}: {}", item_ident, sugg_ty), Applicability::MachineApplicable, ); } else { @@ -793,11 +819,14 @@ fn infer_placeholder_type( let mut diag = bad_placeholder_type(tcx, vec![span]); if !ty.references_error() { - if !contains_anonymous(ty) { + let mut mk_nameable = MakeNameable::new(tcx); + let ty = mk_nameable.fold_ty(ty); + let sugg_ty = if mk_nameable.success { Some(ty) } else { None }; + if let Some(sugg_ty) = sugg_ty { diag.span_suggestion( span, "replace with the correct type", - ty.to_string(), + sugg_ty.to_string(), Applicability::MaybeIncorrect, ); } else { diff --git a/src/test/ui/suggestions/unnamable-types.rs b/src/test/ui/suggestions/unnamable-types.rs index ed70bcf5484c..5d0616443e5a 100644 --- a/src/test/ui/suggestions/unnamable-types.rs +++ b/src/test/ui/suggestions/unnamable-types.rs @@ -13,21 +13,27 @@ static B: _ = "abc"; //~| HELP: replace with the correct type +// FIXME: this should also suggest a function pointer, as the closure is non-capturing const C: _ = || 42; //~^ ERROR: the type placeholder `_` is not allowed within types on item signatures //~| NOTE: not allowed in type signatures //~| NOTE: however, the inferred type struct S { t: T } -const D = S { t: || -> i32 { 42 } }; +const D = S { t: { let i = 0; move || -> i32 { i } } }; //~^ ERROR: missing type for `const` item //~| NOTE: however, the inferred type + fn foo() -> i32 { 42 } -const E = S { t: foo }; +const E = foo; //~^ ERROR: missing type for `const` item -//~| NOTE: however, the inferred type +//~| HELP: provide a type for the item +const F = S { t: foo }; +//~^ ERROR: missing type for `const` item +//~| HELP: provide a type for the item -const F = || -> i32 { yield 0; return 1; }; + +const G = || -> i32 { yield 0; return 1; }; //~^ ERROR: missing type for `const` item //~| NOTE: however, the inferred type diff --git a/src/test/ui/suggestions/unnamable-types.stderr b/src/test/ui/suggestions/unnamable-types.stderr index 8082707fd3c2..2c8166781bfd 100644 --- a/src/test/ui/suggestions/unnamable-types.stderr +++ b/src/test/ui/suggestions/unnamable-types.stderr @@ -14,53 +14,53 @@ LL | static B: _ = "abc"; | help: replace with the correct type: `&str` error[E0121]: the type placeholder `_` is not allowed within types on item signatures - --> $DIR/unnamable-types.rs:16:10 + --> $DIR/unnamable-types.rs:17:10 | LL | const C: _ = || 42; | ^ not allowed in type signatures | -note: however, the inferred type `[closure@$DIR/unnamable-types.rs:16:14: 16:19]` cannot be named - --> $DIR/unnamable-types.rs:16:14 +note: however, the inferred type `[closure@$DIR/unnamable-types.rs:17:14: 17:19]` cannot be named + --> $DIR/unnamable-types.rs:17:14 | LL | const C: _ = || 42; | ^^^^^ error: missing type for `const` item - --> $DIR/unnamable-types.rs:22:7 + --> $DIR/unnamable-types.rs:23:7 | -LL | const D = S { t: || -> i32 { 42 } }; +LL | const D = S { t: { let i = 0; move || -> i32 { i } } }; | ^ | -note: however, the inferred type `S<[closure@$DIR/unnamable-types.rs:22:18: 22:34]>` cannot be named - --> $DIR/unnamable-types.rs:22:11 +note: however, the inferred type `S<[closure@$DIR/unnamable-types.rs:23:31: 23:51]>` cannot be named + --> $DIR/unnamable-types.rs:23:11 | -LL | const D = S { t: || -> i32 { 42 } }; - | ^^^^^^^^^^^^^^^^^^^^^^^^^ +LL | const D = S { t: { let i = 0; move || -> i32 { i } } }; + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: missing type for `const` item - --> $DIR/unnamable-types.rs:27:7 + --> $DIR/unnamable-types.rs:29:7 | -LL | const E = S { t: foo }; - | ^ - | -note: however, the inferred type `S i32 {foo}>` cannot be named - --> $DIR/unnamable-types.rs:27:11 - | -LL | const E = S { t: foo }; - | ^^^^^^^^^^^^ +LL | const E = foo; + | ^ help: provide a type for the item: `E: fn() -> i32` error: missing type for `const` item - --> $DIR/unnamable-types.rs:31:7 + --> $DIR/unnamable-types.rs:32:7 | -LL | const F = || -> i32 { yield 0; return 1; }; +LL | const F = S { t: foo }; + | ^ help: provide a type for the item: `F: S i32>` + +error: missing type for `const` item + --> $DIR/unnamable-types.rs:37:7 + | +LL | const G = || -> i32 { yield 0; return 1; }; | ^ | -note: however, the inferred type `[generator@$DIR/unnamable-types.rs:31:11: 31:43 {i32, ()}]` cannot be named - --> $DIR/unnamable-types.rs:31:11 +note: however, the inferred type `[generator@$DIR/unnamable-types.rs:37:11: 37:43 {i32, ()}]` cannot be named + --> $DIR/unnamable-types.rs:37:11 | -LL | const F = || -> i32 { yield 0; return 1; }; +LL | const G = || -> i32 { yield 0; return 1; }; | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -error: aborting due to 6 previous errors +error: aborting due to 7 previous errors For more information about this error, try `rustc --explain E0121`.