From acb9f9ba385a9207a5f60448a1c374f2eceff13d Mon Sep 17 00:00:00 2001
From: Takayuki Maeda <takoyaki0316@gmail.com>
Date: Wed, 3 Nov 2021 01:44:01 +0900
Subject: [PATCH 1/2] add a suggestion about undeclared `alloc` module
---
compiler/rustc_resolve/src/diagnostics.rs | 4 +++
compiler/rustc_resolve/src/lib.rs | 28 +++++++++++++------
.../ui/suggestions/undeclared-module-alloc.rs | 5 ++++
.../undeclared-module-alloc.stderr | 11 ++++++++
4 files changed, 39 insertions(+), 9 deletions(-)
create mode 100644 src/test/ui/suggestions/undeclared-module-alloc.rs
create mode 100644 src/test/ui/suggestions/undeclared-module-alloc.stderr
diff --git a/compiler/rustc_resolve/src/diagnostics.rs b/compiler/rustc_resolve/src/diagnostics.rs
index 163acebcceacf..ff0d76e94fdf5 100644
--- a/compiler/rustc_resolve/src/diagnostics.rs
+++ b/compiler/rustc_resolve/src/diagnostics.rs
@@ -420,6 +420,10 @@ impl<'a> Resolver<'a> {
err.span_label(span, label);
if let Some((suggestions, msg, applicability)) = suggestion {
+ if suggestions.is_empty() {
+ err.help(&msg);
+ return err;
+ }
err.multipart_suggestion(&msg, suggestions, applicability);
}
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index 23eb2d1aebb7c..55de096d1a458 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -2523,19 +2523,29 @@ impl<'a> Resolver<'a> {
} else {
(
format!("use of undeclared crate or module `{}`", ident),
- self.find_similarly_named_module_or_crate(
- ident.name,
- &parent_scope.module,
- )
- .map(|sugg| {
- (
- vec![(ident.span, sugg.to_string())],
+ if ident.name == sym::alloc {
+ Some((
+ vec![],
String::from(
- "there is a crate or module with a similar name",
+ "add `extern crate alloc` to use the builtin `alloc` module",
),
Applicability::MaybeIncorrect,
+ ))
+ } else {
+ self.find_similarly_named_module_or_crate(
+ ident.name,
+ &parent_scope.module,
)
- }),
+ .map(|sugg| {
+ (
+ vec![(ident.span, sugg.to_string())],
+ String::from(
+ "there is a crate or module with a similar name",
+ ),
+ Applicability::MaybeIncorrect,
+ )
+ })
+ },
)
}
} else {
diff --git a/src/test/ui/suggestions/undeclared-module-alloc.rs b/src/test/ui/suggestions/undeclared-module-alloc.rs
new file mode 100644
index 0000000000000..1defa1cef2863
--- /dev/null
+++ b/src/test/ui/suggestions/undeclared-module-alloc.rs
@@ -0,0 +1,5 @@
+// edition:2018
+
+use alloc::rc::Rc; //~ ERROR failed to resolve: use of undeclared crate or module `alloc`
+
+fn main() {}
diff --git a/src/test/ui/suggestions/undeclared-module-alloc.stderr b/src/test/ui/suggestions/undeclared-module-alloc.stderr
new file mode 100644
index 0000000000000..4da0619af9879
--- /dev/null
+++ b/src/test/ui/suggestions/undeclared-module-alloc.stderr
@@ -0,0 +1,11 @@
+error[E0433]: failed to resolve: use of undeclared crate or module `alloc`
+ --> $DIR/undeclared-module-alloc.rs:3:5
+ |
+LL | use alloc::rc::Rc;
+ | ^^^^^ use of undeclared crate or module `alloc`
+ |
+ = help: add `extern crate alloc` to use the builtin `alloc` module
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0433`.
From 6c1e194534ab91ecdb3aa953089964c364b6b2e2 Mon Sep 17 00:00:00 2001
From: Takayuki Maeda <takoyaki0316@gmail.com>
Date: Wed, 3 Nov 2021 13:53:57 +0900
Subject: [PATCH 2/2] fix message
---
compiler/rustc_resolve/src/lib.rs | 2 +-
src/test/ui/suggestions/undeclared-module-alloc.stderr | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index 55de096d1a458..5f3620b247e26 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -2527,7 +2527,7 @@ impl<'a> Resolver<'a> {
Some((
vec![],
String::from(
- "add `extern crate alloc` to use the builtin `alloc` module",
+ "add `extern crate alloc` to use the `alloc` crate",
),
Applicability::MaybeIncorrect,
))
diff --git a/src/test/ui/suggestions/undeclared-module-alloc.stderr b/src/test/ui/suggestions/undeclared-module-alloc.stderr
index 4da0619af9879..39169dfa9f777 100644
--- a/src/test/ui/suggestions/undeclared-module-alloc.stderr
+++ b/src/test/ui/suggestions/undeclared-module-alloc.stderr
@@ -4,7 +4,7 @@ error[E0433]: failed to resolve: use of undeclared crate or module `alloc`
LL | use alloc::rc::Rc;
| ^^^^^ use of undeclared crate or module `alloc`
|
- = help: add `extern crate alloc` to use the builtin `alloc` module
+ = help: add `extern crate alloc` to use the `alloc` crate
error: aborting due to previous error