diff options
| -rw-r--r-- | src/librustc_typeck/check/demand.rs | 33 | ||||
| -rw-r--r-- | src/test/ui/deref-suggestion.rs | 34 | ||||
| -rw-r--r-- | src/test/ui/deref-suggestion.stderr | 59 |
3 files changed, 126 insertions, 0 deletions
diff --git a/src/librustc_typeck/check/demand.rs b/src/librustc_typeck/check/demand.rs index 65900dc3f36..7110a1ba81d 100644 --- a/src/librustc_typeck/check/demand.rs +++ b/src/librustc_typeck/check/demand.rs @@ -261,6 +261,39 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> { } None } + (_, &ty::TyRef(_, checked)) => { + // We have `&T`, check if what was expected was `T`. If so, + // we may want to suggest adding a `*`, or removing + // a `&`. + // + // (But, also check check the `expn_info()` to see if this is + // a macro; if so, it's hard to extract the text and make a good + // suggestion, so don't bother.) + if self.infcx.can_sub(self.param_env, checked.ty, &expected).is_ok() && + expr.span.ctxt().outer().expn_info().is_none() { + match expr.node { + // Maybe remove `&`? + hir::ExprAddrOf(_, ref expr) => { + if let Ok(code) = self.tcx.sess.codemap().span_to_snippet(expr.span) { + return Some(format!("try with `{}`", code)); + } + } + + // Maybe add `*`? Only if `T: Copy`. + _ => { + if !self.infcx.type_moves_by_default(self.param_env, + checked.ty, + expr.span) { + let sp = self.sess().codemap().call_span_if_macro(expr.span); + if let Ok(code) = self.tcx.sess.codemap().span_to_snippet(sp) { + return Some(format!("try with `*{}`", code)); + } + } + }, + } + } + None + } _ => None, } } diff --git a/src/test/ui/deref-suggestion.rs b/src/test/ui/deref-suggestion.rs new file mode 100644 index 00000000000..16d8226bfec --- /dev/null +++ b/src/test/ui/deref-suggestion.rs @@ -0,0 +1,34 @@ +// 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. + +macro_rules! borrow { + ($x:expr) => { &$x } +} + +fn foo(_: String) {} + +fn foo2(s: &String) { + foo(s); +} + +fn foo3(_: u32) {} +fn foo4(u: &u32) { + foo3(u); +} + +fn main() { + let s = String::new(); + let r_s = &s; + foo2(r_s); + foo(&"aaa".to_owned()); + foo(&mut "aaa".to_owned()); + foo3(borrow!(0)); + foo4(&0); +} diff --git a/src/test/ui/deref-suggestion.stderr b/src/test/ui/deref-suggestion.stderr new file mode 100644 index 00000000000..5ad9c19fa8c --- /dev/null +++ b/src/test/ui/deref-suggestion.stderr @@ -0,0 +1,59 @@ +error[E0308]: mismatched types + --> $DIR/deref-suggestion.rs:18:9 + | +18 | foo(s); + | ^ expected struct `std::string::String`, found reference + | + = note: expected type `std::string::String` + found type `&std::string::String` + = help: here are some functions which might fulfill your needs: + - .escape_debug() + - .escape_default() + - .escape_unicode() + - .to_lowercase() + - .to_uppercase() + +error[E0308]: mismatched types + --> $DIR/deref-suggestion.rs:23:10 + | +23 | foo3(u); + | ^ expected u32, found &u32 + | + = note: expected type `u32` + found type `&u32` + = help: try with `*u` + +error[E0308]: mismatched types + --> $DIR/deref-suggestion.rs:30:9 + | +30 | foo(&"aaa".to_owned()); + | ^^^^^^^^^^^^^^^^^ expected struct `std::string::String`, found reference + | + = note: expected type `std::string::String` + found type `&std::string::String` + = help: try with `"aaa".to_owned()` + +error[E0308]: mismatched types + --> $DIR/deref-suggestion.rs:31:9 + | +31 | foo(&mut "aaa".to_owned()); + | ^^^^^^^^^^^^^^^^^^^^^ expected struct `std::string::String`, found mutable reference + | + = note: expected type `std::string::String` + found type `&mut std::string::String` + = help: try with `"aaa".to_owned()` + +error[E0308]: mismatched types + --> $DIR/deref-suggestion.rs:12:20 + | +12 | ($x:expr) => { &$x } + | ^^^ expected u32, found &{integer} +... +32 | foo3(borrow!(0)); + | ---------- in this macro invocation + | + = note: expected type `u32` + found type `&{integer}` + +error: aborting due to 5 previous errors + |