adjust smart_resolve_partial_mod_path_errors

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -335,8 +335,7 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
         following_seg: Option<&Segment>,
     ) -> Vec<ImportSuggestion> {
         if let Some(segment) = prefix_path.last() &&
-            let Some(following_seg) = following_seg &&
-            prefix_path.len() == 1
+            let Some(following_seg) = following_seg
         {
             let candidates = self.r.lookup_import_candidates(
                 segment.ident,

tests/ui/feature-gates/feature-gate-extern_absolute_paths.stderr

@@ -13,6 +13,15 @@ LL |     let _: u8 = ::core::default::Default();
    |                   ^^^^ maybe a missing crate `core`?
    |
    = help: consider adding `extern crate core` to use the `core` crate
+help: consider importing this module
+   |
+LL + use std::default;
+   |
+help: if you import `default`, refer to it directly
+   |
+LL -     let _: u8 = ::core::default::Default();
+LL +     let _: u8 = default::Default();
+   |
 
 error: aborting due to 2 previous errors
 

tests/ui/hygiene/extern-prelude-from-opaque-fail-2018.stderr

@@ -24,6 +24,9 @@ LL |         fn f() { my_core::mem::drop(0); }
 LL | a!();
    | ---- in this macro invocation
    |
+   = help: consider importing one of these items:
+           std::mem
+           core::mem
    = note: this error originates in the macro `a` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0433]: failed to resolve: use of undeclared crate or module `my_core`
@@ -31,6 +34,18 @@ error[E0433]: failed to resolve: use of undeclared crate or module `my_core`
    |
 LL |     fn f() { my_core::mem::drop(0); }
    |              ^^^^^^^ use of undeclared crate or module `my_core`
+   |
+help: consider importing one of these items
+   |
+LL +     use core::mem;
+   |
+LL +     use std::mem;
+   |
+help: if you import `mem`, refer to it directly
+   |
+LL -     fn f() { my_core::mem::drop(0); }
+LL +     fn f() { mem::drop(0); }
+   |
 
 error: aborting due to 4 previous errors
 

tests/ui/hygiene/extern-prelude-from-opaque-fail.stderr

@@ -24,6 +24,8 @@ LL |         fn f() { my_core::mem::drop(0); }
 LL | a!();
    | ---- in this macro invocation
    |
+   = help: consider importing this module:
+           my_core::mem
    = note: this error originates in the macro `a` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0433]: failed to resolve: use of undeclared crate or module `my_core`
@@ -31,6 +33,16 @@ error[E0433]: failed to resolve: use of undeclared crate or module `my_core`
    |
 LL |     fn f() { my_core::mem::drop(0); }
    |              ^^^^^^^ use of undeclared crate or module `my_core`
+   |
+help: consider importing this module
+   |
+LL +     use my_core::mem;
+   |
+help: if you import `mem`, refer to it directly
+   |
+LL -     fn f() { my_core::mem::drop(0); }
+LL +     fn f() { mem::drop(0); }
+   |
 
 error: aborting due to 4 previous errors
 

tests/ui/suggestions/crate-or-module-typo.stderr

@@ -30,6 +30,17 @@ help: there is a crate or module with a similar name
    |
 LL |     bar: std::cell::Cell<bool>
    |          ~~~
+help: consider importing one of these items
+   |
+LL + use core::cell;
+   |
+LL + use std::cell;
+   |
+help: if you import `cell`, refer to it directly
+   |
+LL -     bar: st::cell::Cell<bool>
+LL +     bar: cell::Cell<bool>
+   |
 
 error[E0433]: failed to resolve: use of undeclared crate or module `bar`
   --> $DIR/crate-or-module-typo.rs:6:20