Do not point at whole file missing fn main

Only point at the end of the crate. We could try making it point at the
beginning of the crate, but that is confused with `DUMMY_SP`, causing
the output to be *worse*.

This change will make it so that VSCode will *not* underline the whole
file when `main` is missing, so other errors will be visible.

Author: estebank

compiler/rustc_passes/src/entry.rs

@@ -218,9 +218,9 @@ fn no_main_err(tcx: TyCtxt<'_>, visitor: &EntryContext<'_, '_>) {
     // The file may be empty, which leads to the diagnostic machinery not emitting this
     // note. This is a relatively simple way to detect that case and emit a span-less
     // note instead.
-    if tcx.sess.source_map().lookup_line(sp.lo()).is_ok() {
-        err.set_span(sp);
-        err.span_label(sp, &note);
+    if tcx.sess.source_map().lookup_line(sp.hi()).is_ok() {
+        err.set_span(sp.shrink_to_hi());
+        err.span_label(sp.shrink_to_hi(), &note);
     } else {
         err.note(&note);
     }

src/test/ui/attributes/issue-90873.rs

@@ -1,9 +1,9 @@
 #![u=||{static d=||1;}]
 //~^ unexpected token
 //~| cannot find attribute `u` in this scope
-//~| `main` function not found in crate `issue_90873`
 //~| missing type for `static` item
 
 #![a={impl std::ops::Neg for i8 {}}]
 //~^ ERROR unexpected token
 //~| ERROR cannot find attribute `a` in this scope
+//~| ERROR `main` function not found in crate `issue_90873`

src/test/ui/attributes/issue-90873.stderr

@@ -10,7 +10,7 @@ LL | #![u=||{static d=||1;}]
 error: unexpected token: `{
            impl std::ops::Neg for i8 {}
        }`
-  --> $DIR/issue-90873.rs:7:6
+  --> $DIR/issue-90873.rs:6:6
    |
 LL | #![a={impl std::ops::Neg for i8 {}}]
    |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -22,22 +22,16 @@ LL | #![u=||{static d=||1;}]
    |    ^
 
 error: cannot find attribute `a` in this scope
-  --> $DIR/issue-90873.rs:7:4
+  --> $DIR/issue-90873.rs:6:4
    |
 LL | #![a={impl std::ops::Neg for i8 {}}]
    |    ^
 
 error[E0601]: `main` function not found in crate `issue_90873`
-  --> $DIR/issue-90873.rs:1:1
+  --> $DIR/issue-90873.rs:6:37
    |
-LL | / #![u=||{static d=||1;}]
-LL | |
-LL | |
-LL | |
-LL | |
-LL | |
-LL | | #![a={impl std::ops::Neg for i8 {}}]
-   | |____________________________________^ consider adding a `main` function to `$DIR/issue-90873.rs`
+LL | #![a={impl std::ops::Neg for i8 {}}]
+   |                                     ^ consider adding a `main` function to `$DIR/issue-90873.rs`
 
 error: missing type for `static` item
   --> $DIR/issue-90873.rs:1:16

src/test/ui/conditional-compilation/cfg-attr-cfg-2.stderr

@@ -1,9 +1,8 @@
 error[E0601]: `main` function not found in crate `cfg_attr_cfg_2`
-  --> $DIR/cfg-attr-cfg-2.rs:8:1
+  --> $DIR/cfg-attr-cfg-2.rs:9:14
    |
-LL | / #[cfg_attr(foo, cfg(bar))]
-LL | | fn main() { }
-   | |_____________^ consider adding a `main` function to `$DIR/cfg-attr-cfg-2.rs`
+LL | fn main() { }
+   |              ^ consider adding a `main` function to `$DIR/cfg-attr-cfg-2.rs`
 
 error: aborting due to previous error
 

src/test/ui/conditional-compilation/cfg-in-crate-1.stderr

@@ -1,8 +1,8 @@
 error[E0601]: `main` function not found in crate `cfg_in_crate_1`
-  --> $DIR/cfg-in-crate-1.rs:3:1
+  --> $DIR/cfg-in-crate-1.rs:3:13
    |
 LL | #![cfg(bar)]
-   | ^^^^^^^^^^^^ consider adding a `main` function to `$DIR/cfg-in-crate-1.rs`
+   |             ^ consider adding a `main` function to `$DIR/cfg-in-crate-1.rs`
 
 error: aborting due to previous error
 

src/test/ui/continue-after-missing-main.rs

@@ -1,4 +1,4 @@
-#![allow(dead_code)] //~ ERROR `main` function not found in crate
+#![allow(dead_code)]
 
 struct Tableau<'a, MP> {
     provider: &'a MP,
@@ -27,4 +27,4 @@ fn create_and_solve_subproblems<'data_provider, 'original_data, MP>(
 ) {
     let _: AdaptedMatrixProvider<'original_data, MP> = tableau.provider().clone_with_extra_bound();
     //~^ ERROR lifetime mismatch
-}
+} //~ ERROR `main` function not found in crate

src/test/ui/continue-after-missing-main.stderr

@@ -1,14 +1,8 @@
 error[E0601]: `main` function not found in crate `continue_after_missing_main`
-  --> $DIR/continue-after-missing-main.rs:1:1
+  --> $DIR/continue-after-missing-main.rs:30:2
    |
-LL | / #![allow(dead_code)]
-LL | |
-LL | | struct Tableau<'a, MP> {
-LL | |     provider: &'a MP,
-...  |
-LL | |
-LL | | }
-   | |_^ consider adding a `main` function to `$DIR/continue-after-missing-main.rs`
+LL | }
+   |  ^ consider adding a `main` function to `$DIR/continue-after-missing-main.rs`
 
 error[E0623]: lifetime mismatch
   --> $DIR/continue-after-missing-main.rs:28:56

src/test/ui/elided-test.stderr

@@ -1,10 +1,8 @@
 error[E0601]: `main` function not found in crate `elided_test`
-  --> $DIR/elided-test.rs:5:1
+  --> $DIR/elided-test.rs:7:2
    |
-LL | / #[test]
-LL | | fn main() {
-LL | | }
-   | |_^ consider adding a `main` function to `$DIR/elided-test.rs`
+LL | }
+   |  ^ consider adding a `main` function to `$DIR/elided-test.rs`
 
 error: aborting due to previous error
 

src/test/ui/entry-point/imported_main_const_fn_item_type_forbidden.rs

@@ -1,7 +1,6 @@
 #![feature(imported_main)]
 #![feature(type_alias_impl_trait)]
 #![allow(incomplete_features)]
-//~^^^ ERROR `main` function not found in crate
 pub mod foo {
     type MainFn = impl Fn();
     //~^ ERROR could not find defining uses
@@ -11,4 +10,4 @@ pub mod foo {
     //~^ ERROR mismatched types [E0308]
 }
 
-use foo::BAR as main;
+use foo::BAR as main; //~ ERROR `main` function not found in crate

src/test/ui/entry-point/imported_main_const_fn_item_type_forbidden.stderr

@@ -1,19 +1,13 @@
 error[E0601]: `main` function not found in crate `imported_main_const_fn_item_type_forbidden`
-  --> $DIR/imported_main_const_fn_item_type_forbidden.rs:1:1
+  --> $DIR/imported_main_const_fn_item_type_forbidden.rs:13:22
    |
-LL | / #![feature(imported_main)]
-LL | | #![feature(type_alias_impl_trait)]
-LL | | #![allow(incomplete_features)]
-LL | |
-...  |
-LL | |
-LL | | use foo::BAR as main;
-   | |_____----------------^ consider adding a `main` function to `$DIR/imported_main_const_fn_item_type_forbidden.rs`
-   |       |
-   |       non-function item at `crate::main` is found
+LL | use foo::BAR as main;
+   |     ---------------- ^ consider adding a `main` function to `$DIR/imported_main_const_fn_item_type_forbidden.rs`
+   |     |
+   |     non-function item at `crate::main` is found
 
 error[E0308]: mismatched types
-  --> $DIR/imported_main_const_fn_item_type_forbidden.rs:10:29
+  --> $DIR/imported_main_const_fn_item_type_forbidden.rs:9:29
    |
 LL |     type MainFn = impl Fn();
    |                   --------- the expected opaque type
@@ -25,7 +19,7 @@ LL |     pub const BAR: MainFn = bar;
                   found fn item `fn() {bar}`
 
 error: could not find defining uses
-  --> $DIR/imported_main_const_fn_item_type_forbidden.rs:6:19
+  --> $DIR/imported_main_const_fn_item_type_forbidden.rs:5:19
    |
 LL |     type MainFn = impl Fn();
    |                   ^^^^^^^^^