Rollup merge of rust-lang#48706 - ehuss:main-not-found-in-crate, r=estebank

Add crate name to "main function not found" error message.

Fixes rust-lang#44798 and rust-lang/cargo#4948.

I was wondering if it might be cleaner to update the ui tests to add a simple `fn main() {}` for the unrelated tests.  Let me know if you would prefer that.

Author: kennytm

src/librustc/middle/entry.rs

@@ -55,7 +55,9 @@ impl<'a, 'tcx> ItemLikeVisitor<'tcx> for EntryContext<'a, 'tcx> {
     }
 }
 
-pub fn find_entry_point(session: &Session, hir_map: &hir_map::Map) {
+pub fn find_entry_point(session: &Session,
+                        hir_map: &hir_map::Map,
+                        crate_name: &str) {
     let any_exe = session.crate_types.borrow().iter().any(|ty| {
         *ty == config::CrateTypeExecutable
     });
@@ -81,7 +83,7 @@ pub fn find_entry_point(session: &Session, hir_map: &hir_map::Map) {
 
     hir_map.krate().visit_all_item_likes(&mut ctxt);
 
-    configure_main(&mut ctxt);
+    configure_main(&mut ctxt, crate_name);
 }
 
 // Beware, this is duplicated in libsyntax/entry.rs, make sure to keep
@@ -150,7 +152,7 @@ fn find_item(item: &Item, ctxt: &mut EntryContext, at_root: bool) {
     }
 }
 
-fn configure_main(this: &mut EntryContext) {
+fn configure_main(this: &mut EntryContext, crate_name: &str) {
     if this.start_fn.is_some() {
         *this.session.entry_fn.borrow_mut() = this.start_fn;
         this.session.entry_type.set(Some(config::EntryStart));
@@ -162,7 +164,8 @@ fn configure_main(this: &mut EntryContext) {
         this.session.entry_type.set(Some(config::EntryMain));
     } else {
         // No main function
-        let mut err = struct_err!(this.session, E0601, "main function not found");
+        let mut err = struct_err!(this.session, E0601,
+            "`main` function not found in crate `{}`", crate_name);
         if !this.non_main_fns.is_empty() {
             // There were some functions named 'main' though. Try to give the user a hint.
             err.note("the main function must be defined at the crate level \
@@ -175,6 +178,9 @@ fn configure_main(this: &mut EntryContext) {
             err.emit();
             this.session.abort_if_errors();
         } else {
+            if let Some(ref filename) = this.session.local_crate_source_file {
+                err.note(&format!("consider adding a `main` function to `{}`", filename.display()));
+            }
             if this.session.teach(&err.get_code().unwrap()) {
                 err.note("If you don't know the basics of Rust, you can go look to the Rust Book \
                           to get started: https://doc.rust-lang.org/book/");

src/librustc_driver/driver.rs

@@ -979,7 +979,7 @@ pub fn phase_3_run_analysis_passes<'tcx, F, R>(trans: &TransCrate,
 
     time(sess,
          "looking for entry point",
-         || middle::entry::find_entry_point(sess, &hir_map));
+         || middle::entry::find_entry_point(sess, &hir_map, name));
 
     sess.plugin_registrar_fn.set(time(sess, "looking for plugin registrar", || {
         plugin::build::find_plugin_registrar(sess.diagnostic(), &hir_map)

src/test/compile-fail/cfg-attr-cfg-2.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 //
-// error-pattern: main function not found
+// error-pattern: `main` function not found
 // compile-flags: --cfg foo
 
 // main is conditionally compiled, but the conditional compilation

src/test/compile-fail/cfg-in-crate-1.rs

@@ -8,6 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// error-pattern:main function not found
+// error-pattern: `main` function not found
 
 #![cfg(bar)]

src/test/compile-fail/elided-test.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// error-pattern: main function not found
+// error-pattern: `main` function not found
 
 // Since we're not compiling a test runner this function should be elided
 // and the build will fail because main doesn't exist

src/test/compile-fail/missing-main.rs

@@ -8,5 +8,5 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// error-pattern:main function not found
+// error-pattern: `main` function not found
 fn mian() { }

src/test/ui/error-codes/E0522.rs

@@ -15,3 +15,5 @@ fn cookie() -> ! {
 //~^^ ERROR definition of an unknown language item: `cookie` [E0522]
     loop {}
 }
+
+fn main() {}

src/test/ui/error-codes/E0522.stderr

@@ -1,12 +1,9 @@
-error[E0601]: main function not found
-
 error[E0522]: definition of an unknown language item: `cookie`
   --> $DIR/E0522.rs:13:1
    |
 LL | #[lang = "cookie"]
    | ^^^^^^^^^^^^^^^^^^ definition of unknown language item `cookie`
 
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-Some errors occurred: E0522, E0601.
-For more information about an error, try `rustc --explain E0522`.
+For more information about this error, try `rustc --explain E0522`.

src/test/ui/error-codes/E0601.rs

@@ -0,0 +1,11 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Test for main function not found.

src/test/ui/error-codes/E0601.stderr

@@ -0,0 +1,7 @@
+error[E0601]: `main` function not found in crate `E0601`
+   |
+   = note: consider adding a `main` function to `$DIR/E0601.rs`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0601`.

src/test/ui/feature-gate-i128_type2.rs

@@ -30,3 +30,5 @@ fn test3_2() {
 enum A { //~ ERROR 128-bit type is unstable
     A(u64)
 }
+
+fn main() {}

src/test/ui/feature-gate-i128_type2.stderr

@@ -30,8 +30,6 @@ LL |     let x: u128 = 0; //~ ERROR 128-bit type is unstable
    |
    = help: add #![feature(i128_type)] to the crate attributes to enable
 
-error[E0601]: main function not found
-
 error[E0658]: repr with 128-bit type is unstable (see issue #35118)
   --> $DIR/feature-gate-i128_type2.rs:30:1
    |
@@ -42,7 +40,6 @@ LL | | }
    |
    = help: add #![feature(repr128)] to the crate attributes to enable
 
-error: aborting due to 6 previous errors
+error: aborting due to 5 previous errors
 
-Some errors occurred: E0601, E0658.
-For more information about an error, try `rustc --explain E0601`.
+For more information about this error, try `rustc --explain E0658`.

src/test/ui/feature-gate/issue-43106-gating-of-bench.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// error-pattern: main function not found
+// error-pattern: `main` function not found
 
 // At time of authorship, a crate-level #![bench] with no `--test`
 // will cause compilation to error unconditionally with "main function

src/test/ui/feature-gate/issue-43106-gating-of-bench.stderr

@@ -1,4 +1,6 @@
-error[E0601]: main function not found
+error[E0601]: `main` function not found in crate `issue_43106_gating_of_bench`
+   |
+   = note: consider adding a `main` function to `$DIR/issue-43106-gating-of-bench.rs`
 
 error: aborting due to previous error
 

src/test/ui/feature-gate/issue-43106-gating-of-inline.rs

@@ -35,3 +35,5 @@ mod inline {
     #[inline = "2100"] impl S { }
     //~^ ERROR attribute should be applied to function
 }
+
+fn main() {}

src/test/ui/feature-gate/issue-43106-gating-of-inline.stderr

@@ -1,5 +1,3 @@
-error[E0601]: main function not found
-
 error[E0518]: attribute should be applied to function
   --> $DIR/issue-43106-gating-of-inline.rs:21:1
    |
@@ -39,7 +37,6 @@ error[E0518]: attribute should be applied to function
 LL |     #[inline = "2100"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^ ---------- not a function
 
-error: aborting due to 6 previous errors
+error: aborting due to 5 previous errors
 
-Some errors occurred: E0518, E0601.
-For more information about an error, try `rustc --explain E0518`.
+For more information about this error, try `rustc --explain E0518`.

src/test/ui/feature-gate/issue-43106-gating-of-macro_escape.rs

@@ -13,5 +13,9 @@
 // `#![macro_escape]` is incompatible with crate-level `#![macro_use]`
 // already present in issue-43106-gating-of-builtin-attrs.
 
+// must-compile-successfully
+
 #![macro_escape]
 //~^ WARN macro_escape is a deprecated synonym for macro_use
+
+fn main() {}

src/test/ui/feature-gate/issue-43106-gating-of-macro_escape.stderr

@@ -1,13 +1,8 @@
 warning: macro_escape is a deprecated synonym for macro_use
-  --> $DIR/issue-43106-gating-of-macro_escape.rs:16:1
+  --> $DIR/issue-43106-gating-of-macro_escape.rs:18:1
    |
 LL | #![macro_escape]
    | ^^^^^^^^^^^^^^^^
    |
    = help: consider an outer attribute, #[macro_use] mod ...
 
-error[E0601]: main function not found
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0601`.

src/test/ui/feature-gate/issue-43106-gating-of-proc_macro_derive.rs

@@ -40,3 +40,5 @@ mod proc_macro_derive2 {
     #[proc_macro_derive = "2500"] impl S { }
     //~^ ERROR the `#[proc_macro_derive]` attribute may only be used on bare functions
 }
+
+fn main() {}

src/test/ui/feature-gate/issue-43106-gating-of-proc_macro_derive.stderr

@@ -34,8 +34,5 @@ error: the `#[proc_macro_derive]` attribute may only be used on bare functions
 LL |     #[proc_macro_derive = "2500"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error[E0601]: main function not found
+error: aborting due to 6 previous errors
 
-error: aborting due to 7 previous errors
-
-For more information about this error, try `rustc --explain E0601`.

src/test/ui/feature-gate/issue-43106-gating-of-rustc_deprecated.rs

@@ -36,3 +36,4 @@ mod rustc_deprecated {
     //~^ ERROR stability attributes may not be used outside of the standard library
 }
 
+fn main() {}

src/test/ui/feature-gate/issue-43106-gating-of-rustc_deprecated.stderr

@@ -1,5 +1,3 @@
-error[E0601]: main function not found
-
 error: stability attributes may not be used outside of the standard library
   --> $DIR/issue-43106-gating-of-rustc_deprecated.rs:17:1
    |
@@ -42,6 +40,5 @@ error: stability attributes may not be used outside of the standard library
 LL |     #[rustc_deprecated = "1500"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 8 previous errors
+error: aborting due to 7 previous errors
 
-For more information about this error, try `rustc --explain E0601`.

src/test/ui/feature-gate/issue-43106-gating-of-stable.rs

@@ -35,3 +35,5 @@ mod stable {
     #[stable = "1300"] impl S { }
     //~^ ERROR stability attributes may not be used outside of the standard library
 }
+
+fn main() {}

src/test/ui/feature-gate/issue-43106-gating-of-stable.stderr

@@ -1,5 +1,3 @@
-error[E0601]: main function not found
-
 error: stability attributes may not be used outside of the standard library
   --> $DIR/issue-43106-gating-of-stable.rs:17:1
    |
@@ -42,6 +40,5 @@ error: stability attributes may not be used outside of the standard library
 LL |     #[stable = "1300"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 8 previous errors
+error: aborting due to 7 previous errors
 
-For more information about this error, try `rustc --explain E0601`.

src/test/ui/feature-gate/issue-43106-gating-of-test.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// error-pattern: main function not found
+// error-pattern: `main` function not found
 
 // At time of authorship, crate-level #[test] attribute with no
 // `--test` signals unconditional error complaining of missing main

src/test/ui/feature-gate/issue-43106-gating-of-test.stderr

@@ -1,4 +1,6 @@
-error[E0601]: main function not found
+error[E0601]: `main` function not found in crate `issue_43106_gating_of_test`
+   |
+   = note: consider adding a `main` function to `$DIR/issue-43106-gating-of-test.rs`
 
 error: aborting due to previous error
 

src/test/ui/feature-gate/issue-43106-gating-of-unstable.rs

@@ -35,3 +35,5 @@ mod unstable {
     #[unstable = "1200"] impl S { }
     //~^ ERROR stability attributes may not be used outside of the standard library
 }
+
+fn main() {}

src/test/ui/feature-gate/issue-43106-gating-of-unstable.stderr

@@ -1,5 +1,3 @@
-error[E0601]: main function not found
-
 error: stability attributes may not be used outside of the standard library
   --> $DIR/issue-43106-gating-of-unstable.rs:17:1
    |
@@ -42,6 +40,5 @@ error: stability attributes may not be used outside of the standard library
 LL |     #[unstable = "1200"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 8 previous errors
+error: aborting due to 7 previous errors
 
-For more information about this error, try `rustc --explain E0601`.

src/test/ui/generator/yield-in-const.rs

@@ -12,3 +12,5 @@
 
 const A: u8 = { yield 3u8; 3u8};
 //~^ ERROR yield statement outside
+
+fn main() {}

src/test/ui/generator/yield-in-const.stderr

@@ -1,12 +1,9 @@
-error[E0601]: main function not found
-
 error[E0627]: yield statement outside of generator literal
   --> $DIR/yield-in-const.rs:13:17
    |
 LL | const A: u8 = { yield 3u8; 3u8};
    |                 ^^^^^^^^^
 
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-Some errors occurred: E0601, E0627.
-For more information about an error, try `rustc --explain E0601`.
+For more information about this error, try `rustc --explain E0627`.

src/test/ui/generator/yield-in-static.rs

@@ -12,3 +12,5 @@
 
 static B: u8 = { yield 3u8; 3u8};
 //~^ ERROR yield statement outside
+
+fn main() {}

src/test/ui/generator/yield-in-static.stderr

@@ -1,12 +1,9 @@
-error[E0601]: main function not found
-
 error[E0627]: yield statement outside of generator literal
   --> $DIR/yield-in-static.rs:13:18
    |
 LL | static B: u8 = { yield 3u8; 3u8};
    |                  ^^^^^^^^^
 
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-Some errors occurred: E0601, E0627.
-For more information about an error, try `rustc --explain E0601`.
+For more information about this error, try `rustc --explain E0627`.

src/test/ui/imports/macro-paths.rs

@@ -36,3 +36,5 @@ fn g() {
         mod baz { pub use two_macros::m; }
     }
 }
+
+fn main() {}

src/test/ui/imports/macro-paths.stderr

@@ -36,9 +36,6 @@ LL | | }
    | |_^
    = note: macro-expanded items do not shadow when used in a macro invocation path
 
-error[E0601]: main function not found
+error: aborting due to 2 previous errors
 
-error: aborting due to 3 previous errors
-
-Some errors occurred: E0601, E0659.
-For more information about an error, try `rustc --explain E0601`.
+For more information about this error, try `rustc --explain E0659`.

src/test/ui/imports/macros.rs

@@ -49,3 +49,5 @@ mod m4 {
     use two_macros::m;
     m!(); //~ ERROR ambiguous
 }
+
+fn main() {}

src/test/ui/imports/macros.stderr

@@ -51,9 +51,6 @@ LL |     use two_macros::m;
    |         ^^^^^^^^^^^^^
    = note: macro-expanded macro imports do not shadow
 
-error[E0601]: main function not found
+error: aborting due to 3 previous errors
 
-error: aborting due to 4 previous errors
-
-Some errors occurred: E0601, E0659.
-For more information about an error, try `rustc --explain E0601`.
+For more information about this error, try `rustc --explain E0659`.

src/test/ui/in-band-lifetimes/mismatched_trait_impl-2.rs

@@ -20,3 +20,5 @@ impl Deref for Struct {
     }
 }
 //~^^^^ ERROR cannot infer an appropriate lifetime for lifetime parameter
+
+fn main() {}