Auto merge of rust-lang#42264 - GuillaumeGomez:new-error-codes, r=Susurrus

New error codes

Part of rust-lang#42229.

Author: bors

src/librustc_borrowck/borrowck/mod.rs

@@ -701,7 +701,7 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
     fn bckerr_to_diag(&self, err: &BckError<'tcx>) -> DiagnosticBuilder<'a> {
         let span = err.span.clone();
 
-        let msg = match err.code {
+        match err.code {
             err_mutbl => {
                 let descr = match err.cmt.note {
                     mc::NoteClosureEnv(_) | mc::NoteUpvarRef(_) => {
@@ -725,10 +725,11 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
 
                 match err.cause {
                     MutabilityViolation => {
-                        format!("cannot assign to {}", descr)
+                        struct_span_err!(self.tcx.sess, span, E0594, "cannot assign to {}", descr)
                     }
                     BorrowViolation(euv::ClosureCapture(_)) => {
-                        format!("closure cannot assign to {}", descr)
+                        struct_span_err!(self.tcx.sess, span, E0595,
+                                         "closure cannot assign to {}", descr)
                     }
                     BorrowViolation(euv::OverloadedOperator) |
                     BorrowViolation(euv::AddrOf) |
@@ -737,7 +738,8 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
                     BorrowViolation(euv::AutoUnsafe) |
                     BorrowViolation(euv::ForLoop) |
                     BorrowViolation(euv::MatchDiscriminant) => {
-                        format!("cannot borrow {} as mutable", descr)
+                        struct_span_err!(self.tcx.sess, span, E0596,
+                                         "cannot borrow {} as mutable", descr)
                     }
                     BorrowViolation(euv::ClosureInvocation) => {
                         span_bug!(err.span,
@@ -752,17 +754,16 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
                         format!("`{}`", self.loan_path_to_string(&lp))
                     }
                 };
-                format!("{} does not live long enough", msg)
+                struct_span_err!(self.tcx.sess, span, E0597, "{} does not live long enough", msg)
             }
             err_borrowed_pointer_too_short(..) => {
                 let descr = self.cmt_to_path_or_string(&err.cmt);
-                format!("lifetime of {} is too short to guarantee \
-                         its contents can be safely reborrowed",
-                        descr)
+                struct_span_err!(self.tcx.sess, span, E0598,
+                                 "lifetime of {} is too short to guarantee \
+                                  its contents can be safely reborrowed",
+                                 descr)
             }
-        };
-
-        self.struct_span_err(span, &msg)
+        }
     }
 
     pub fn report_aliasability_violation(&self,
@@ -1169,7 +1170,7 @@ before rustc 1.16, this temporary lived longer - see issue #39283 \
                 if kind == ty::ClosureKind::Fn {
                     db.span_help(self.tcx.hir.span(upvar_id.closure_expr_id),
                                  "consider changing this closure to take \
-                                 self by mutable reference");
+                                  self by mutable reference");
                 }
             }
             _ => {

src/librustc_borrowck/diagnostics.rs

@@ -1114,9 +1114,63 @@ fn main() {
 ```
 "##,
 
+E0596: r##"
+This error occurs because you tried to mutably borrow a non-mutable variable.
+
+Example of erroneous code:
+
+```compile_fail,E0596
+let x = 1;
+let y = &mut x; // error: cannot borrow mutably
+```
+
+In here, `x` isn't mutable, so when we try to mutably borrow it in `y`, it
+fails. To fix this error, you need to make `x` mutable:
+
+```
+let mut x = 1;
+let y = &mut x; // ok!
+```
+"##,
+
+E0597: r##"
+This error occurs because a borrow was made inside a variable which has a
+greater lifetime than the borrowed one.
+
+Example of erroneous code:
+
+```compile_fail,E0597
+struct Foo<'a> {
+    x: Option<&'a u32>,
+}
+
+let mut x = Foo { x: None };
+let y = 0;
+x.x = Some(&y); // error: `y` does not live long enough
+```
+
+In here, `x` is created before `y` and therefore has a greater lifetime. Always
+keep in mind that values in a scope are dropped in the opposite order they are
+created. So to fix the previous example, just make the `y` lifetime greater than
+the `x`'s one:
+
+```
+struct Foo<'a> {
+    x: Option<&'a u32>,
+}
+
+let y = 0;
+let mut x = Foo { x: None };
+x.x = Some(&y);
+```
+"##,
+
 }
 
 register_diagnostics! {
 //    E0385, // {} in an aliasable location
     E0524, // two closures require unique access to `..` at the same time
+    E0594, // cannot assign to {}
+    E0595, // closure cannot assign to {}
+    E0598, // lifetime of {} is too short to guarantee its contents can be...
 }

src/librustc_typeck/check/method/suggest.rs

@@ -165,18 +165,21 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                                                .. }) => {
                 let tcx = self.tcx;
 
-                let mut err = self.type_error_struct(span,
-                                                     |actual| {
-                    format!("no {} named `{}` found for type `{}` in the current scope",
-                            if mode == Mode::MethodCall {
-                                "method"
-                            } else {
-                                "associated item"
-                            },
-                            item_name,
-                            actual)
-                },
-                                                     rcvr_ty);
+                let actual = self.resolve_type_vars_if_possible(&rcvr_ty);
+                let mut err = if !actual.references_error() {
+                    struct_span_err!(tcx.sess, span, E0599,
+                                     "no {} named `{}` found for type `{}` in the \
+                                      current scope",
+                                     if mode == Mode::MethodCall {
+                                         "method"
+                                     } else {
+                                         "associated item"
+                                     },
+                                     item_name,
+                                     self.ty_to_string(actual))
+                } else {
+                    self.tcx.sess.diagnostic().struct_dummy()
+                };
 
                 // If the method name is the name of a field with a function or closure type,
                 // give a helping note that it has to be called as (x.f)(...).

src/librustc_typeck/check/op.rs

@@ -316,10 +316,12 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         match self.lookup_op_method(ex, operand_ty, vec![], mname, trait_did, operand_expr) {
             Ok(t) => t,
             Err(()) => {
-                self.type_error_message(ex.span, |actual| {
-                    format!("cannot apply unary operator `{}` to type `{}`",
-                            op_str, actual)
-                }, operand_ty);
+                let actual = self.resolve_type_vars_if_possible(&operand_ty);
+                if !actual.references_error() {
+                    struct_span_err!(self.tcx.sess, ex.span, E0600,
+                                     "cannot apply unary operator `{}` to type `{}`",
+                                     op_str, actual).emit();
+                }
                 self.tcx.types.err
             }
         }

src/librustc_typeck/diagnostics.rs

@@ -4005,7 +4005,7 @@ details.
 [issue #33685]: https://github.com/rust-lang/rust/issues/33685
 "##,
 
-    E0582: r##"
+E0582: r##"
 A lifetime appears only in an associated-type binding,
 and not in the input types to the trait.
 
@@ -4042,6 +4042,59 @@ details.
 [issue #33685]: https://github.com/rust-lang/rust/issues/33685
 "##,
 
+E0599: r##"
+```compile_fail,E0599
+struct Mouth;
+
+let x = Mouth;
+x.chocolate(); // error: no method named `chocolate` found for type `Mouth`
+               //        in the current scope
+```
+"##,
+
+E0600: r##"
+An unary operator was used on a type which doesn't implement it.
+
+Example of erroneous code:
+
+```compile_fail,E0600
+enum Question {
+    Yes,
+    No,
+}
+
+!Question::Yes; // error: cannot apply unary operator `!` to type `Question`
+```
+
+In this case, `Question` would need to implement the `std::ops::Not` trait in
+order to be able to use `!` on it. Let's implement it:
+
+```
+use std::ops::Not;
+
+enum Question {
+    Yes,
+    No,
+}
+
+// We implement the `Not` trait on the enum.
+impl Not for Question {
+    type Output = bool;
+
+    fn not(self) -> bool {
+        match self {
+            Question::Yes => false, // If the `Answer` is `Yes`, then it
+                                    // returns false.
+            Question::No => true, // And here we do the opposite.
+        }
+    }
+}
+
+assert_eq!(!Question::Yes, false);
+assert_eq!(!Question::No, true);
+```
+"##,
+
 }
 
 register_diagnostics! {

src/test/compile-fail/E0596.rs

@@ -0,0 +1,14 @@
+// Copyright 2017 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.
+
+fn main() {
+    let x = 1;
+    let y = &mut x; //~ ERROR E0596
+}

src/test/compile-fail/E0597.rs

@@ -0,0 +1,19 @@
+// Copyright 2017 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.
+
+struct Foo<'a> {
+    x: Option<&'a u32>,
+}
+
+fn main() {
+    let mut x = Foo { x: None };
+    let y = 0;
+    x.x = Some(&y);
+} //~ `y` does not live long enough [E0597]

src/test/compile-fail/E0600.rs

@@ -0,0 +1,13 @@
+// Copyright 2017 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.
+
+fn main() {
+    !"a"; //~ ERROR E0600
+}

src/test/ui/codemap_tests/huge_multispan_highlight.stderr

@@ -1,4 +1,4 @@
-error: cannot borrow immutable local variable `x` as mutable
+error[E0596]: cannot borrow immutable local variable `x` as mutable
    --> $DIR/huge_multispan_highlight.rs:100:18
     |
 12  |     let x = "foo";

src/test/ui/codemap_tests/issue-28308.stderr

@@ -1,4 +1,4 @@
-error: cannot apply unary operator `!` to type `&'static str`
+error[E0600]: cannot apply unary operator `!` to type `&'static str`
   --> $DIR/issue-28308.rs:12:5
    |
 12 |     assert!("foo");

src/test/ui/did_you_mean/issue-31424.stderr

@@ -1,4 +1,4 @@
-error: cannot borrow immutable argument `self` as mutable
+error[E0596]: cannot borrow immutable argument `self` as mutable
   --> $DIR/issue-31424.rs:17:15
    |
 17 |         (&mut self).bar();
@@ -7,7 +7,7 @@ error: cannot borrow immutable argument `self` as mutable
    |               try removing `&mut` here
    |               cannot reborrow mutably
 
-error: cannot borrow immutable argument `self` as mutable
+error[E0596]: cannot borrow immutable argument `self` as mutable
   --> $DIR/issue-31424.rs:23:15
    |
 22 |     fn bar(self: &mut Self) {

src/test/ui/did_you_mean/issue-34126.stderr

@@ -1,4 +1,4 @@
-error: cannot borrow immutable argument `self` as mutable
+error[E0596]: cannot borrow immutable argument `self` as mutable
   --> $DIR/issue-34126.rs:16:23
    |
 16 |         self.run(&mut self);

src/test/ui/did_you_mean/issue-34337.stderr

@@ -1,4 +1,4 @@
-error: cannot borrow immutable local variable `key` as mutable
+error[E0596]: cannot borrow immutable local variable `key` as mutable
   --> $DIR/issue-34337.rs:16:14
    |
 16 |     get(&mut key);

src/test/ui/did_you_mean/issue-35937.stderr

@@ -1,20 +1,20 @@
-error: cannot borrow immutable field `f.v` as mutable
+error[E0596]: cannot borrow immutable field `f.v` as mutable
   --> $DIR/issue-35937.rs:17:5
    |
 16 |     let f = Foo { v: Vec::new() };
    |         - consider changing this to `mut f`
 17 |     f.v.push("cat".to_string());
    |     ^^^ cannot mutably borrow immutable field
 
-error: cannot assign to immutable field `s.x`
+error[E0594]: cannot assign to immutable field `s.x`
   --> $DIR/issue-35937.rs:26:5
    |
 25 |     let s = S { x: 42 };
    |         - consider changing this to `mut s`
 26 |     s.x += 1;
    |     ^^^^^^^^ cannot mutably borrow immutable field
 
-error: cannot assign to immutable field `s.x`
+error[E0594]: cannot assign to immutable field `s.x`
   --> $DIR/issue-35937.rs:30:5
    |
 29 | fn bar(s: S) {

src/test/ui/did_you_mean/issue-37139.stderr

@@ -1,4 +1,4 @@
-error: cannot borrow immutable local variable `x` as mutable
+error[E0596]: cannot borrow immutable local variable `x` as mutable
   --> $DIR/issue-37139.rs:22:23
    |
 22 |             test(&mut x);

src/test/ui/did_you_mean/issue-38147-2.stderr

@@ -1,4 +1,4 @@
-error: cannot borrow immutable borrowed content `*self.s` as mutable
+error[E0596]: cannot borrow immutable borrowed content `*self.s` as mutable
   --> $DIR/issue-38147-2.rs:17:9
    |
 12 |     s: &'a String

src/test/ui/did_you_mean/issue-38147-3.stderr

@@ -1,4 +1,4 @@
-error: cannot borrow immutable borrowed content `*self.s` as mutable
+error[E0596]: cannot borrow immutable borrowed content `*self.s` as mutable
   --> $DIR/issue-38147-3.rs:17:9
    |
 12 |     s: &'a String