Convert some notes to help messages

Closes #18126.

Author: ftxqxd

src/doc/guide.md

@@ -777,7 +777,7 @@ fn add_one(x: int) -> int {
      x + 1;
 }
 
-note: consider removing this semicolon:
+help: consider removing this semicolon:
      x + 1;
           ^
 ```

src/librustc/middle/borrowck/check_loans.rs

@@ -789,7 +789,7 @@ impl<'a, 'tcx> CheckLoanCtxt<'a, 'tcx> {
                         assignment_span,
                         format!("cannot assign to {}",
                                 self.bccx.cmt_to_string(&*assignee_cmt)).as_slice());
-                    self.bccx.span_note(
+                    self.bccx.span_help(
                         self.tcx().map.span(upvar_id.closure_expr_id),
                         "consider changing this closure to take self by mutable reference");
                 } else {

src/librustc/middle/borrowck/gather_loans/move_error.rs

@@ -148,9 +148,12 @@ fn note_move_destination(bccx: &BorrowckCtxt,
     if is_first_note {
         bccx.span_note(
             move_to_span,
-            format!("attempting to move value to here (to prevent the move, \
+            "attempting to move value to here");
+        bccx.span_help(
+            move_to_span,
+            format!("to prevent the move, \
                      use `ref {0}` or `ref mut {0}` to capture value by \
-                     reference)",
+                     reference",
                     pat_name).as_slice());
     } else {
         bccx.span_note(move_to_span,

src/librustc/middle/borrowck/mod.rs

@@ -527,8 +527,8 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
                                                   r).as_slice())
                     }
                 };
-                let suggestion = move_suggestion(self.tcx, expr_ty,
-                        "moved by default (use `copy` to override)");
+                let (suggestion, _) = move_suggestion(self.tcx, expr_ty,
+                        ("moved by default", ""));
                 self.tcx.sess.span_note(
                     expr_span,
                     format!("`{}` moved here{} because it has type `{}`, which is {}",
@@ -540,13 +540,15 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
 
             move_data::MovePat => {
                 let pat_ty = ty::node_id_to_type(self.tcx, the_move.id);
-                self.tcx.sess.span_note(self.tcx.map.span(the_move.id),
+                let span = self.tcx.map.span(the_move.id);
+                self.tcx.sess.span_note(span,
                     format!("`{}` moved here{} because it has type `{}`, \
-                             which is moved by default (use `ref` to \
-                             override)",
+                             which is moved by default",
                             ol,
                             moved_lp_msg,
                             pat_ty.user_string(self.tcx)).as_slice());
+                self.tcx.sess.span_help(span,
+                    "use `ref` to override");
             }
 
             move_data::Captured => {
@@ -563,9 +565,9 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
                                                   r).as_slice())
                     }
                 };
-                let suggestion = move_suggestion(self.tcx, expr_ty,
-                        "moved by default (make a copy and \
-                         capture that instead to override)");
+                let (suggestion, help) = move_suggestion(self.tcx, expr_ty,
+                        ("moved by default", "make a copy and \
+                         capture that instead to override"));
                 self.tcx.sess.span_note(
                     expr_span,
                     format!("`{}` moved into closure environment here{} because it \
@@ -574,21 +576,23 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
                             moved_lp_msg,
                             expr_ty.user_string(self.tcx),
                             suggestion).as_slice());
+                self.tcx.sess.span_help(expr_span, help);
             }
         }
 
-        fn move_suggestion(tcx: &ty::ctxt, ty: ty::t, default_msg: &'static str)
-                          -> &'static str {
+        fn move_suggestion(tcx: &ty::ctxt, ty: ty::t, default_msgs: (&'static str, &'static str))
+                          -> (&'static str, &'static str) {
             match ty::get(ty).sty {
                 ty::ty_closure(box ty::ClosureTy {
                         store: ty::RegionTraitStore(..),
                         ..
                     }) =>
-                    "a non-copyable stack closure (capture it in a new closure, \
-                     e.g. `|x| f(x)`, to override)",
+                    ("a non-copyable stack closure",
+                     "capture it in a new closure, e.g. `|x| f(x)`, to override"),
                 _ if ty::type_moves_by_default(tcx, ty) =>
-                    "non-copyable (perhaps you meant to use clone()?)",
-                _ => default_msg,
+                    ("non-copyable",
+                     "perhaps you meant to use `clone()`?"),
+                _ => default_msgs,
             }
         }
     }
@@ -733,7 +737,7 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
                 self.tcx.sess.span_err(span,
                                        format!("{} in a captured outer \
                                                variable in an `Fn` closure", prefix).as_slice());
-                span_note!(self.tcx.sess, self.tcx.map.span(id),
+                span_help!(self.tcx.sess, self.tcx.map.span(id),
                            "consider changing this closure to take self by mutable reference");
             }
             mc::AliasableStatic(..) |
@@ -750,7 +754,7 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
         }
 
         if is_closure {
-            self.tcx.sess.span_note(
+            self.tcx.sess.span_help(
                 span,
                 "closures behind references must be called via `&mut`");
         }
@@ -770,7 +774,7 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
                             _ => unreachable!()
                         };
                         if kind == ty::FnUnboxedClosureKind {
-                            self.tcx.sess.span_note(
+                            self.tcx.sess.span_help(
                                 self.tcx.map.span(upvar_id.closure_expr_id),
                                 "consider changing this closure to take \
                                  self by mutable reference");
@@ -787,15 +791,20 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
                     sub_scope,
                     "...");
                 let suggestion = if is_statement_scope(self.tcx, super_scope) {
-                    "; consider using a `let` binding to increase its lifetime"
+                    Some("consider using a `let` binding to increase its lifetime")
                 } else {
-                    ""
+                    None
                 };
-                note_and_explain_region(
+                let span = note_and_explain_region(
                     self.tcx,
                     "...but borrowed value is only valid for ",
                     super_scope,
-                    suggestion);
+                    "");
+                match (span, suggestion) {
+                    (_, None) => {},
+                    (Some(span), Some(msg)) => self.tcx.sess.span_help(span, msg),
+                    (None, Some(msg)) => self.tcx.sess.help(msg),
+                }
             }
 
             err_borrowed_pointer_too_short(loan_scope, ptr_scope) => {

src/librustc/middle/dependency_format.rs

@@ -213,7 +213,7 @@ fn add_library(sess: &session::Session,
                 sess.err(format!("cannot satisfy dependencies so `{}` only \
                                   shows up once",
                                  data.name).as_slice());
-                sess.note("having upstream crates all available in one format \
+                sess.help("having upstream crates all available in one format \
                            will likely make this go away");
             }
         }

src/librustc/middle/liveness.rs

@@ -1568,7 +1568,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
                             hi: original_span.hi,
                             expn_id: original_span.expn_id
                         };
-                        self.ir.tcx.sess.span_note(
+                        self.ir.tcx.sess.span_help(
                             span_semicolon, "consider removing this semicolon:");
                     }
                 }

src/librustc/middle/resolve.rs

@@ -5744,7 +5744,7 @@ impl<'a> Resolver<'a> {
                                                  uses it like a function name",
                                                 wrong_name).as_slice());
 
-                                self.session.span_note(expr.span,
+                                self.session.span_help(expr.span,
                                     format!("Did you mean to write: \
                                             `{} {{ /* fields */ }}`?",
                                             wrong_name).as_slice());

src/librustc/middle/typeck/astconv.rs

@@ -172,18 +172,18 @@ pub fn opt_ast_region_to_region<'tcx, AC: AstConv<'tcx>, RS: RegionScope>(
                                 }
                             }
                             if len == 1 {
-                                span_note!(this.tcx().sess, default_span,
+                                span_help!(this.tcx().sess, default_span,
                                     "this function's return type contains a borrowed value, but \
                                      the signature does not say which {} it is borrowed from",
                                     m);
                             } else if len == 0 {
-                                span_note!(this.tcx().sess, default_span,
+                                span_help!(this.tcx().sess, default_span,
                                     "this function's return type contains a borrowed value, but \
                                      there is no value for it to be borrowed from");
-                                span_note!(this.tcx().sess, default_span,
+                                span_help!(this.tcx().sess, default_span,
                                     "consider giving it a 'static lifetime");
                             } else {
-                                span_note!(this.tcx().sess, default_span,
+                                span_help!(this.tcx().sess, default_span,
                                     "this function's return type contains a borrowed value, but \
                                      the signature does not say whether it is borrowed from {}",
                                     m);
@@ -302,7 +302,7 @@ fn ast_path_substs<'tcx,AC,RS>(
         && !this.tcx().sess.features.borrow().default_type_params {
         span_err!(this.tcx().sess, path.span, E0108,
             "default type parameters are experimental and possibly buggy");
-        span_note!(this.tcx().sess, path.span,
+        span_help!(this.tcx().sess, path.span,
             "add #![feature(default_type_params)] to the crate attributes to enable");
     }
 
@@ -1168,6 +1168,7 @@ fn ty_of_method_or_bare_fn<'tcx, AC: AstConv<'tcx>>(
 
     let param_lifetimes: Vec<(String, uint)> = lifetimes_for_params.into_iter()
                                                                    .map(|(n, v)| (n, v.len()))
+                                                                   .filter(|&(_, l)| l != 0)
                                                                    .collect();
 
     let output_ty = match decl.output.node {

src/librustc/middle/typeck/check/mod.rs

@@ -1355,18 +1355,18 @@ fn check_cast(fcx: &FnCtxt,
                     ast::MutImmutable => ""
                 };
                 if ty::type_is_trait(t_1) {
-                    span_note!(fcx.tcx().sess, t.span, "did you mean `&{}{}`?", mtstr, tstr);
+                    span_help!(fcx.tcx().sess, t.span, "did you mean `&{}{}`?", mtstr, tstr);
                 } else {
-                    span_note!(fcx.tcx().sess, span,
+                    span_help!(fcx.tcx().sess, span,
                                "consider using an implicit coercion to `&{}{}` instead",
                                mtstr, tstr);
                 }
             }
             ty::ty_uniq(..) => {
-                span_note!(fcx.tcx().sess, t.span, "did you mean `Box<{}>`?", tstr);
+                span_help!(fcx.tcx().sess, t.span, "did you mean `Box<{}>`?", tstr);
             }
             _ => {
-                span_note!(fcx.tcx().sess, e.span,
+                span_help!(fcx.tcx().sess, e.span,
                            "consider using a box or reference as appropriate");
             }
         }
@@ -2142,7 +2142,7 @@ fn try_overloaded_call<'a>(fcx: &FnCtxt,
         if !fcx.tcx().sess.features.borrow().overloaded_calls {
             span_err!(fcx.tcx().sess, call_expression.span, E0056,
                 "overloaded calls are experimental");
-            span_note!(fcx.tcx().sess, call_expression.span,
+            span_help!(fcx.tcx().sess, call_expression.span,
                 "add `#![feature(overloaded_calls)]` to \
                 the crate attributes to enable");
         }
@@ -3479,8 +3479,9 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
                     },
                     expr_t, None);
 
-                tcx.sess.span_note(field.span,
-                    "maybe a missing `()` to call it? If not, try an anonymous function.");
+                tcx.sess.span_help(field.span,
+                    "maybe a `()` to call it is missing? \
+                     If not, try an anonymous function");
             }
 
             Err(_) => {
@@ -4787,7 +4788,8 @@ pub fn check_instantiable(tcx: &ty::ctxt,
     if !ty::is_instantiable(tcx, item_ty) {
         span_err!(tcx.sess, sp, E0073,
             "this type cannot be instantiated without an \
-             instance of itself; consider using `Option<{}>`",
+             instance of itself");
+        span_help!(tcx.sess, sp, "consider using `Option<{}>`",
             ppaux::ty_to_string(tcx, item_ty));
         false
     } else {

src/librustc/middle/typeck/check/vtable.rs

@@ -521,7 +521,7 @@ fn note_obligation_cause(fcx: &FnCtxt,
             span_note!(tcx.sess, obligation.cause.span,
                       "cannot implement a destructor on a \
                       structure or enumeration that does not satisfy Send");
-            span_note!(tcx.sess, obligation.cause.span,
+            span_help!(tcx.sess, obligation.cause.span,
                        "use \"#[unsafe_destructor]\" on the implementation \
                        to force the compiler to allow this");
         }