diagnostics: only talk about Cargo.toml if running under Cargo

compiler/rustc_errors/src/diagnostic.rs

@@ -7,6 +7,7 @@ use crate::SuggestionStyle;
 use crate::ToolMetadata;
 use rustc_lint_defs::Applicability;
 use rustc_serialize::json::Json;
+use rustc_span::edition::LATEST_STABLE_EDITION;
 use rustc_span::{MultiSpan, Span, DUMMY_SP};
 use std::fmt;
 use std::hash::{Hash, Hasher};
@@ -342,6 +343,18 @@ impl Diagnostic {
         self
     }
 
+    /// Help the user upgrade to the latest edition.
+    /// This is factored out to make sure it does the right thing with `Cargo.toml`.
+    pub fn help_use_latest_edition(&mut self) -> &mut Self {
+        if std::env::var_os("CARGO").is_some() {
+            self.help(&format!("set `edition = \"{}\"` in `Cargo.toml`", LATEST_STABLE_EDITION));
+        } else {
+            self.help(&format!("pass `--edition {}` to `rustc`", LATEST_STABLE_EDITION));
+        }
+        self.note("for more on editions, read https://doc.rust-lang.org/edition-guide");
+        self
+    }
+
     /// Disallow attaching suggestions this diagnostic.
     /// Any suggestions attached e.g. with the `span_suggestion_*` methods
     /// (before and after the call to `disable_suggestions`) will be ignored.

compiler/rustc_errors/src/diagnostic_builder.rs

@@ -409,6 +409,7 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
         sp: impl Into<MultiSpan>,
         msg: &str,
     ) -> &mut Self);
+    forward!(pub fn help_use_latest_edition(&mut self,) -> &mut Self);
     forward!(pub fn set_is_lint(&mut self,) -> &mut Self);
 
     forward!(pub fn disable_suggestions(&mut self,) -> &mut Self);

compiler/rustc_parse/src/parser/expr.rs

@@ -20,7 +20,6 @@ use rustc_ast_pretty::pprust;
 use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, PResult};
 use rustc_session::lint::builtin::BREAK_WITH_LABEL_AND_LOOP;
 use rustc_session::lint::BuiltinLintDiagnostics;
-use rustc_span::edition::LATEST_STABLE_EDITION;
 use rustc_span::source_map::{self, Span, Spanned};
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{BytePos, Pos};
@@ -2712,8 +2711,7 @@ impl<'a> Parser<'a> {
         let mut async_block_err = |e: &mut Diagnostic, span: Span| {
             recover_async = true;
             e.span_label(span, "`async` blocks are only allowed in Rust 2018 or later");
-            e.help(&format!("set `edition = \"{}\"` in `Cargo.toml`", LATEST_STABLE_EDITION));
-            e.note("for more on editions, read https://doc.rust-lang.org/edition-guide");
+            e.help_use_latest_edition();
         };
 
         while self.token != token::CloseDelim(close_delim) {

compiler/rustc_parse/src/parser/item.rs

@@ -14,7 +14,7 @@ use rustc_ast::{FnHeader, ForeignItem, Path, PathSegment, Visibility, Visibility
 use rustc_ast::{MacArgs, MacCall, MacDelimiter};
 use rustc_ast_pretty::pprust;
 use rustc_errors::{struct_span_err, Applicability, PResult, StashKey};
-use rustc_span::edition::{Edition, LATEST_STABLE_EDITION};
+use rustc_span::edition::Edition;
 use rustc_span::lev_distance::lev_distance;
 use rustc_span::source_map::{self, Span};
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
@@ -2102,8 +2102,7 @@ impl<'a> Parser<'a> {
             let diag = self.diagnostic();
             struct_span_err!(diag, span, E0670, "`async fn` is not permitted in Rust 2015")
                 .span_label(span, "to use `async fn`, switch to Rust 2018 or later")
-                .help(&format!("set `edition = \"{}\"` in `Cargo.toml`", LATEST_STABLE_EDITION))
-                .note("for more on editions, read https://doc.rust-lang.org/edition-guide")
+                .help_use_latest_edition()
                 .emit();
         }
     }

compiler/rustc_typeck/src/check/expr.rs

@@ -43,7 +43,6 @@ use rustc_middle::ty::error::TypeError::{FieldMisMatch, Sorts};
 use rustc_middle::ty::subst::SubstsRef;
 use rustc_middle::ty::{self, AdtKind, Ty, TypeFoldable};
 use rustc_session::parse::feature_err;
-use rustc_span::edition::LATEST_STABLE_EDITION;
 use rustc_span::hygiene::DesugaringKind;
 use rustc_span::lev_distance::find_best_match_for_name;
 use rustc_span::source_map::Span;
@@ -2010,8 +2009,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // We know by construction that `<expr>.await` is either on Rust 2015
             // or results in `ExprKind::Await`. Suggest switching the edition to 2018.
             err.note("to `.await` a `Future`, switch to Rust 2018 or later");
-            err.help(&format!("set `edition = \"{}\"` in `Cargo.toml`", LATEST_STABLE_EDITION));
-            err.note("for more on editions, read https://doc.rust-lang.org/edition-guide");
+            err.help_use_latest_edition();
         }
 
         err.emit();

src/test/ui/async-await/edition-deny-async-fns-2015.stderr

@@ -4,7 +4,7 @@ error[E0670]: `async fn` is not permitted in Rust 2015
 LL | async fn foo() {}
    | ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
-   = help: set `edition = "2021"` in `Cargo.toml`
+   = help: pass `--edition 2021` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0670]: `async fn` is not permitted in Rust 2015
@@ -13,7 +13,7 @@ error[E0670]: `async fn` is not permitted in Rust 2015
 LL | fn baz() { async fn foo() {} }
    |            ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
-   = help: set `edition = "2021"` in `Cargo.toml`
+   = help: pass `--edition 2021` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0670]: `async fn` is not permitted in Rust 2015
@@ -22,7 +22,7 @@ error[E0670]: `async fn` is not permitted in Rust 2015
 LL | async fn async_baz() {
    | ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
-   = help: set `edition = "2021"` in `Cargo.toml`
+   = help: pass `--edition 2021` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0670]: `async fn` is not permitted in Rust 2015
@@ -31,7 +31,7 @@ error[E0670]: `async fn` is not permitted in Rust 2015
 LL |     async fn bar() {}
    |     ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
-   = help: set `edition = "2021"` in `Cargo.toml`
+   = help: pass `--edition 2021` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0670]: `async fn` is not permitted in Rust 2015
@@ -40,7 +40,7 @@ error[E0670]: `async fn` is not permitted in Rust 2015
 LL |     async fn foo() {}
    |     ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
-   = help: set `edition = "2021"` in `Cargo.toml`
+   = help: pass `--edition 2021` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0670]: `async fn` is not permitted in Rust 2015
@@ -49,7 +49,7 @@ error[E0670]: `async fn` is not permitted in Rust 2015
 LL |     async fn foo() {}
    |     ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
-   = help: set `edition = "2021"` in `Cargo.toml`
+   = help: pass `--edition 2021` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0670]: `async fn` is not permitted in Rust 2015
@@ -58,7 +58,7 @@ error[E0670]: `async fn` is not permitted in Rust 2015
 LL |         async fn bar() {}
    |         ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
-   = help: set `edition = "2021"` in `Cargo.toml`
+   = help: pass `--edition 2021` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0670]: `async fn` is not permitted in Rust 2015
@@ -67,7 +67,7 @@ error[E0670]: `async fn` is not permitted in Rust 2015
 LL |         async fn foo() {}
    |         ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
-   = help: set `edition = "2021"` in `Cargo.toml`
+   = help: pass `--edition 2021` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0670]: `async fn` is not permitted in Rust 2015
@@ -76,7 +76,7 @@ error[E0670]: `async fn` is not permitted in Rust 2015
 LL |             async fn bar() {}
    |             ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
-   = help: set `edition = "2021"` in `Cargo.toml`
+   = help: pass `--edition 2021` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0706]: functions in traits cannot be declared `async`

src/test/ui/async-await/suggest-switching-edition-on-await-cargo.rs

@@ -0,0 +1,47 @@
+// rustc-env:CARGO=/usr/bin/cargo
+
+use std::pin::Pin;
+use std::future::Future;
+
+fn main() {}
+
+fn await_on_struct_missing() {
+    struct S;
+    let x = S;
+    x.await;
+    //~^ ERROR no field `await` on type
+    //~| NOTE unknown field
+    //~| NOTE to `.await` a `Future`, switch to Rust 2018
+    //~| HELP set `edition = "2021"` in `Cargo.toml`
+    //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
+}
+
+fn await_on_struct_similar() {
+    struct S {
+        awai: u8,
+    }
+    let x = S { awai: 42 };
+    x.await;
+    //~^ ERROR no field `await` on type
+    //~| HELP a field with a similar name exists
+    //~| NOTE to `.await` a `Future`, switch to Rust 2018
+    //~| HELP set `edition = "2021"` in `Cargo.toml`
+    //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
+}
+
+fn await_on_63533(x: Pin<&mut dyn Future<Output = ()>>) {
+    x.await;
+    //~^ ERROR no field `await` on type
+    //~| NOTE unknown field
+    //~| NOTE to `.await` a `Future`, switch to Rust 2018
+    //~| HELP set `edition = "2021"` in `Cargo.toml`
+    //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
+}
+
+fn await_on_apit(x: impl Future<Output = ()>) {
+    x.await;
+    //~^ ERROR no field `await` on type
+    //~| NOTE to `.await` a `Future`, switch to Rust 2018
+    //~| HELP set `edition = "2021"` in `Cargo.toml`
+    //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
+}

src/test/ui/async-await/suggest-switching-edition-on-await-cargo.stderr

@@ -0,0 +1,43 @@
+error[E0609]: no field `await` on type `await_on_struct_missing::S`
+  --> $DIR/suggest-switching-edition-on-await-cargo.rs:11:7
+   |
+LL |     x.await;
+   |       ^^^^^ unknown field
+   |
+   = note: to `.await` a `Future`, switch to Rust 2018 or later
+   = help: set `edition = "2021"` in `Cargo.toml`
+   = note: for more on editions, read https://doc.rust-lang.org/edition-guide
+
+error[E0609]: no field `await` on type `await_on_struct_similar::S`
+  --> $DIR/suggest-switching-edition-on-await-cargo.rs:24:7
+   |
+LL |     x.await;
+   |       ^^^^^ help: a field with a similar name exists: `awai`
+   |
+   = note: to `.await` a `Future`, switch to Rust 2018 or later
+   = help: set `edition = "2021"` in `Cargo.toml`
+   = note: for more on editions, read https://doc.rust-lang.org/edition-guide
+
+error[E0609]: no field `await` on type `Pin<&mut dyn Future<Output = ()>>`
+  --> $DIR/suggest-switching-edition-on-await-cargo.rs:33:7
+   |
+LL |     x.await;
+   |       ^^^^^ unknown field
+   |
+   = note: to `.await` a `Future`, switch to Rust 2018 or later
+   = help: set `edition = "2021"` in `Cargo.toml`
+   = note: for more on editions, read https://doc.rust-lang.org/edition-guide
+
+error[E0609]: no field `await` on type `impl Future<Output = ()>`
+  --> $DIR/suggest-switching-edition-on-await-cargo.rs:42:7
+   |
+LL |     x.await;
+   |       ^^^^^
+   |
+   = note: to `.await` a `Future`, switch to Rust 2018 or later
+   = help: set `edition = "2021"` in `Cargo.toml`
+   = note: for more on editions, read https://doc.rust-lang.org/edition-guide
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0609`.

src/test/ui/async-await/suggest-switching-edition-on-await.rs

@@ -10,7 +10,7 @@ fn await_on_struct_missing() {
     //~^ ERROR no field `await` on type
     //~| NOTE unknown field
     //~| NOTE to `.await` a `Future`, switch to Rust 2018
-    //~| HELP set `edition = "2021"` in `Cargo.toml`
+    //~| HELP pass `--edition 2021` to `rustc`
     //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
 }
 
@@ -23,7 +23,7 @@ fn await_on_struct_similar() {
     //~^ ERROR no field `await` on type
     //~| HELP a field with a similar name exists
     //~| NOTE to `.await` a `Future`, switch to Rust 2018
-    //~| HELP set `edition = "2021"` in `Cargo.toml`
+    //~| HELP pass `--edition 2021` to `rustc`
     //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
 }
 
@@ -32,14 +32,14 @@ fn await_on_63533(x: Pin<&mut dyn Future<Output = ()>>) {
     //~^ ERROR no field `await` on type
     //~| NOTE unknown field
     //~| NOTE to `.await` a `Future`, switch to Rust 2018
-    //~| HELP set `edition = "2021"` in `Cargo.toml`
+    //~| HELP pass `--edition 2021` to `rustc`
     //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
 }
 
 fn await_on_apit(x: impl Future<Output = ()>) {
     x.await;
     //~^ ERROR no field `await` on type
     //~| NOTE to `.await` a `Future`, switch to Rust 2018
-    //~| HELP set `edition = "2021"` in `Cargo.toml`
+    //~| HELP pass `--edition 2021` to `rustc`
     //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
 }

src/test/ui/async-await/suggest-switching-edition-on-await.stderr

@@ -5,7 +5,7 @@ LL |     x.await;
    |       ^^^^^ unknown field
    |
    = note: to `.await` a `Future`, switch to Rust 2018 or later
-   = help: set `edition = "2021"` in `Cargo.toml`
+   = help: pass `--edition 2021` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0609]: no field `await` on type `await_on_struct_similar::S`
@@ -15,7 +15,7 @@ LL |     x.await;
    |       ^^^^^ help: a field with a similar name exists: `awai`
    |
    = note: to `.await` a `Future`, switch to Rust 2018 or later
-   = help: set `edition = "2021"` in `Cargo.toml`
+   = help: pass `--edition 2021` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0609]: no field `await` on type `Pin<&mut dyn Future<Output = ()>>`
@@ -25,7 +25,7 @@ LL |     x.await;
    |       ^^^^^ unknown field
    |
    = note: to `.await` a `Future`, switch to Rust 2018 or later
-   = help: set `edition = "2021"` in `Cargo.toml`
+   = help: pass `--edition 2021` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0609]: no field `await` on type `impl Future<Output = ()>`
@@ -35,7 +35,7 @@ LL |     x.await;
    |       ^^^^^
    |
    = note: to `.await` a `Future`, switch to Rust 2018 or later
-   = help: set `edition = "2021"` in `Cargo.toml`
+   = help: pass `--edition 2021` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error: aborting due to 4 previous errors

src/test/ui/editions/async-block-2015.rs

@@ -1,7 +1,7 @@
 async fn foo() {
 //~^ ERROR `async fn` is not permitted in Rust 2015
 //~| NOTE to use `async fn`, switch to Rust 2018 or later
-//~| HELP set `edition = "2021"` in `Cargo.toml`
+//~| HELP pass `--edition 2021` to `rustc`
 //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
 
     let x = async {};
@@ -11,15 +11,15 @@ async fn foo() {
         let x = 42;
         //~^ ERROR expected identifier, found keyword `let`
         //~| NOTE expected identifier, found keyword
-        //~| HELP set `edition = "2021"` in `Cargo.toml`
+        //~| HELP pass `--edition 2021` to `rustc`
         //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
         42
     };
     let z = async { //~ NOTE `async` blocks are only allowed in Rust 2018 or later
         42
         //~^ ERROR expected identifier, found `42`
         //~| NOTE expected identifier
-        //~| HELP set `edition = "2021"` in `Cargo.toml`
+        //~| HELP pass `--edition 2021` to `rustc`
         //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
     };
     y.await;

src/test/ui/editions/async-block-2015.stderr

@@ -4,7 +4,7 @@ error[E0670]: `async fn` is not permitted in Rust 2015
 LL | async fn foo() {
    | ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
-   = help: set `edition = "2021"` in `Cargo.toml`
+   = help: pass `--edition 2021` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error: expected identifier, found keyword `let`
@@ -15,7 +15,7 @@ LL |     let y = async {
 LL |         let x = 42;
    |         ^^^ expected identifier, found keyword
    |
-   = help: set `edition = "2021"` in `Cargo.toml`
+   = help: pass `--edition 2021` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error: expected identifier, found `42`
@@ -26,7 +26,7 @@ LL |     let z = async {
 LL |         42
    |         ^^ expected identifier
    |
-   = help: set `edition = "2021"` in `Cargo.toml`
+   = help: pass `--edition 2021` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0422]: cannot find struct, variant or union type `async` in this scope

src/test/ui/impl-trait/issues/issue-79099.stderr

@@ -6,7 +6,7 @@ LL |         let f: impl core::future::Future<Output = u8> = async { 1 };
    |                                                         |
    |                                                         `async` blocks are only allowed in Rust 2018 or later
    |
-   = help: set `edition = "2021"` in `Cargo.toml`
+   = help: pass `--edition 2021` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in variable binding