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Account for const fns to avoid incorrect suggestions

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estebank committed Apr 30, 2019
1 parent 4e84b61 commit 31eb5cc7305f8967efd449f7067178c980ab27ba
@@ -734,6 +734,14 @@ impl<'hir> Map<'hir> {
}
}

pub fn is_const_scope(&self, hir_id: HirId) -> bool {
self.walk_parent_nodes(hir_id, |node| match *node {
Node::Item(Item { node: ItemKind::Const(_, _), .. }) => true,
Node::Item(Item { node: ItemKind::Fn(_, header, _, _), .. }) => header.is_const(),
_ => false,
}, |_| false).map(|id| id != CRATE_HIR_ID).unwrap_or(false)
}

/// If there is some error when walking the parents (e.g., a node does not
/// have a parent in the map or a node can't be found), then we return the
/// last good `NodeId` we found. Note that reaching the crate root (`id == 0`),
@@ -2288,6 +2288,15 @@ pub struct FnHeader {
pub abi: Abi,
}

impl FnHeader {
pub fn is_const(&self) -> bool {
match &self.constness {
Constness::Const => true,
_ => false,
}
}
}

#[derive(Clone, RustcEncodable, RustcDecodable, Debug, HashStable)]
pub enum ItemKind {
/// An `extern crate` item, with optional *original* crate name if the crate was renamed.
@@ -7,7 +7,7 @@ use syntax_pos::Span;
use rustc::hir;
use rustc::hir::def::Def;
use rustc::hir::Node;
use rustc::hir::{Item, ItemKind, print};
use rustc::hir::print;
use rustc::ty::{self, Ty, AssociatedItem};
use rustc::ty::adjustment::AllowTwoPhase;
use errors::{Applicability, DiagnosticBuilder};
@@ -550,14 +550,11 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
checked_ty: Ty<'tcx>,
expected_ty: Ty<'tcx>,
) -> bool {
let parent_id = self.tcx.hir().get_parent_node_by_hir_id(expr.hir_id);
if let Some(parent) = self.tcx.hir().find_by_hir_id(parent_id) {
if self.tcx.hir().is_const_scope(expr.hir_id) {
// Shouldn't suggest `.into()` on `const`s.
if let Node::Item(Item { node: ItemKind::Const(_, _), .. }) = parent {
// FIXME(estebank): modify once we decide to suggest `as` casts
return false;
}
};
// FIXME(estebank): modify once we decide to suggest `as` casts
return false;
}

// If casting this expression to a given numeric type would be appropriate in case of a type
// mismatch.
@@ -0,0 +1,12 @@
const C: i32 = 1i8; //~ ERROR mismatched types
const D: i8 = C; //~ ERROR mismatched types

const fn foo() {
let c: i32 = 1i8; //~ ERROR mismatched types
let d: i8 = c; //~ ERROR mismatched types
}

fn main() {
let c: i32 = 1i8; //~ ERROR mismatched types
let d: i8 = c; //~ ERROR mismatched types
}
@@ -0,0 +1,47 @@
error[E0308]: mismatched types
--> $DIR/const-scope.rs:1:16
|
LL | const C: i32 = 1i8;
| ^^^ expected i32, found i8

error[E0308]: mismatched types
--> $DIR/const-scope.rs:2:15
|
LL | const D: i8 = C;
| ^ expected i8, found i32

error[E0308]: mismatched types
--> $DIR/const-scope.rs:5:18
|
LL | let c: i32 = 1i8;
| ^^^ expected i32, found i8

error[E0308]: mismatched types
--> $DIR/const-scope.rs:6:17
|
LL | let d: i8 = c;
| ^ expected i8, found i32

error[E0308]: mismatched types
--> $DIR/const-scope.rs:10:18
|
LL | let c: i32 = 1i8;
| ^^^ expected i32, found i8
help: change the type of the numeric literal from `i8` to `i32`
|
LL | let c: i32 = 1i32;
| ^^^^

error[E0308]: mismatched types
--> $DIR/const-scope.rs:11:17
|
LL | let d: i8 = c;
| ^ expected i8, found i32
help: you can convert an `i32` to `i8` or panic if it the converted value wouldn't fit
|
LL | let d: i8 = c.try_into().unwrap();
| ^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 6 previous errors

For more information about this error, try `rustc --explain E0308`.

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