diff options
| -rw-r--r-- | src/librustc_typeck/check/op.rs | 57 | ||||
| -rw-r--r-- | src/test/parse-fail/issue-39018.stderr | 28 | ||||
| -rw-r--r-- | src/test/ui/span/issue-39018.rs | 23 | ||||
| -rw-r--r-- | src/test/ui/span/issue-39018.stderr | 28 |
4 files changed, 133 insertions, 3 deletions
diff --git a/src/librustc_typeck/check/op.rs b/src/librustc_typeck/check/op.rs index 925d28247b6..0dcdab07e6f 100644 --- a/src/librustc_typeck/check/op.rs +++ b/src/librustc_typeck/check/op.rs @@ -13,7 +13,9 @@ use super::FnCtxt; use hir::def_id::DefId; use rustc::ty::{Ty, TypeFoldable, PreferMutLvalue, TypeVariants}; +use rustc::ty::TypeVariants::{TyStr, TyRef}; use rustc::infer::type_variable::TypeVariableOrigin; +use errors; use syntax::ast; use syntax::symbol::Symbol; use rustc::hir; @@ -237,9 +239,17 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> { }; if let Some(missing_trait) = missing_trait { - span_note!(&mut err, lhs_expr.span, - "an implementation of `{}` might be missing for `{}`", - missing_trait, lhs_ty); + if missing_trait == "std::ops::Add" && + self.check_str_addition(expr, lhs_expr, lhs_ty, + rhs_expr, rhs_ty_var, &mut err) { + // This has nothing here because it means we did string + // concatenation (e.g. "Hello " + "World!"). This means + // we don't want the span in the else clause to be emmitted + } else { + span_note!(&mut err, lhs_expr.span, + "an implementation of `{}` might be missing for `{}`", + missing_trait, lhs_ty); + } } err.emit(); } @@ -254,6 +264,47 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> { (rhs_ty_var, return_ty) } + fn check_str_addition(&self, + expr: &'gcx hir::Expr, + lhs_expr: &'gcx hir::Expr, + lhs_ty: Ty<'tcx>, + rhs_expr: &'gcx hir::Expr, + rhs_ty_var: Ty<'tcx>, + mut err: &mut errors::DiagnosticBuilder) -> bool { + // If this function returns false it means we use it to make sure we print + // out the an "implementation of span_note!" above where this function is + // called and if true we don't. + let mut is_string_addition = false; + let rhs_ty = self.check_expr_coercable_to_type(rhs_expr, rhs_ty_var); + if let TyRef(_, l_ty) = lhs_ty.sty { + if let TyRef(_, r_ty) = rhs_ty.sty { + if l_ty.ty.sty == TyStr && r_ty.ty.sty == TyStr { + span_note!(&mut err, lhs_expr.span, + "`+` can't be used to concatenate two `&str` strings"); + let codemap = self.tcx.sess.codemap(); + let suggestion = + match (codemap.span_to_snippet(lhs_expr.span), + codemap.span_to_snippet(rhs_expr.span)) { + (Ok(lstring), Ok(rstring)) => + format!("{}.to_owned() + {}", lstring, rstring), + _ => format!("<expression>") + }; + err.span_suggestion(expr.span, + &format!("to_owned() can be used to create an owned `String` \ + from a string reference. String concatenation \ + appends the string on the right to the string \ + on the left and may require reallocation. This \ + requires ownership of the string on the left."), suggestion); + is_string_addition = true; + } + + } + + } + + is_string_addition + } + pub fn check_user_unop(&self, op_str: &str, mname: &str, diff --git a/src/test/parse-fail/issue-39018.stderr b/src/test/parse-fail/issue-39018.stderr new file mode 100644 index 00000000000..ee1a32c4c16 --- /dev/null +++ b/src/test/parse-fail/issue-39018.stderr @@ -0,0 +1,28 @@ +error[E0369]: binary operation `+` cannot be applied to type `&'static str` + --> src/test/ui/span/issue-39018.rs:2:13 + | +2 | let x = "Hello " + "World!"; + | ^^^^^^^^ + | +note: `+` can't be used to concatenate two `&str` strings + --> src/test/ui/span/issue-39018.rs:2:13 + | +2 | let x = "Hello " + "World!"; + | ^^^^^^^^ +help: to_owned() can be used to create an owned `String` from a string reference. This allows concatenation since the `String` is owned. + | let x = "Hello ".to_owned() + "World!"; + +error[E0369]: binary operation `+` cannot be applied to type `World` + --> src/test/ui/span/issue-39018.rs:7:13 + | +7 | let y = World::Hello + World::Goodbye; + | ^^^^^^^^^^^^ + | +note: an implementation of `std::ops::Add` might be missing for `World` + --> src/test/ui/span/issue-39018.rs:7:13 + | +7 | let y = World::Hello + World::Goodbye; + | ^^^^^^^^^^^^ + +error: aborting due to 2 previous errors + diff --git a/src/test/ui/span/issue-39018.rs b/src/test/ui/span/issue-39018.rs new file mode 100644 index 00000000000..1cbc5ff1d2a --- /dev/null +++ b/src/test/ui/span/issue-39018.rs @@ -0,0 +1,23 @@ +// 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. + +pub fn main() { + let x = "Hello " + "World!"; + + // Make sure that the span outputs a warning + // for not having an implementation for std::ops::Add + // that won't output for the above string concatenation + let y = World::Hello + World::Goodbye; +} + +enum World { + Hello, + Goodbye, +} diff --git a/src/test/ui/span/issue-39018.stderr b/src/test/ui/span/issue-39018.stderr new file mode 100644 index 00000000000..a8cc74056ca --- /dev/null +++ b/src/test/ui/span/issue-39018.stderr @@ -0,0 +1,28 @@ +error[E0369]: binary operation `+` cannot be applied to type `&'static str` + --> $DIR/issue-39018.rs:12:13 + | +12 | let x = "Hello " + "World!"; + | ^^^^^^^^ + | +note: `+` can't be used to concatenate two `&str` strings + --> $DIR/issue-39018.rs:12:13 + | +12 | let x = "Hello " + "World!"; + | ^^^^^^^^ +help: to_owned() can be used to create an owned `String` from a string reference. String concatenation appends the string on the right to the string on the left and may require reallocation. This requires ownership of the string on the left. + | let x = "Hello ".to_owned() + "World!"; + +error[E0369]: binary operation `+` cannot be applied to type `World` + --> $DIR/issue-39018.rs:17:13 + | +17 | let y = World::Hello + World::Goodbye; + | ^^^^^^^^^^^^ + | +note: an implementation of `std::ops::Add` might be missing for `World` + --> $DIR/issue-39018.rs:17:13 + | +17 | let y = World::Hello + World::Goodbye; + | ^^^^^^^^^^^^ + +error: aborting due to 2 previous errors + |