Fix range borrowing suggestions logic

src/librustc_typeck/check/demand.rs

@@ -309,12 +309,16 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                 };
                 if self.can_coerce(ref_ty, expected) {
                     if let Ok(src) = cm.span_to_snippet(sp) {
-                        let sugg_expr = match expr.node { // parenthesize if needed (Issue #46756)
+                        let needs_parens = match expr.node {
-                            hir::ExprKind::Cast(_, _)        |
+                            // parenthesize if needed (Issue #46756)
-                            hir::ExprKind::Binary(_, _, _)   |
+                            hir::ExprKind::Cast(_, _) |
-                            _ if self.is_range_literal(expr) => format!("({})", src),
+                            hir::ExprKind::Binary(_, _, _) => true,
-                            _                                => src,
+                            // parenthesize borrows of range literals (Issue #54505)
+                            _ if self.is_range_literal(expr) => true,
+                            _ => false,
                         };
+                        let sugg_expr = if needs_parens { format!("({})", src) } else { src };
+
                         if let Some(sugg) = self.can_use_as_ref(expr) {
                             return Some(sugg);
                         }
@@ -380,8 +384,9 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
     fn is_range_literal(&self, expr: &hir::Expr) -> bool {
         use hir::{Path, QPath, ExprKind, TyKind};
 
-        // TODO how to work out std vs core here?
+        // we support `::std::ops::Range` and `::std::core::Range` prefixes
-        let ops_path = ["{{root}}", "std", "ops"];
+        // (via split on "|")
+        let ops_path = ["{{root}}", "std|core", "ops"];
 
         let is_range_path = |path: &Path| {
             let ident_names: Vec<_> = path.segments
@@ -394,24 +399,47 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                     preceding.len() == 3 &&
                     preceding.iter()
                         .zip(ops_path.iter())
-                        .all(|(a, b)| a == b)
+                        .all(|(seg, match_seg)| {
+                            match_seg.split("|")
+                                .into_iter()
+                                .any(|ref spl_seg| seg == spl_seg)
+                        })
             } else {
                 false
             }
         };
 
-        match expr.node {
+        let is_range_struct_snippet = |span: &Span| {
-            ExprKind::Struct(QPath::Resolved(None, ref path), _, _) |
+            // Tell if expression span snippet looks like an explicit
-            ExprKind::Path(QPath::Resolved(None, ref path)) => {
+            // Range struct or new() call.  This is to allow rejecting
-                return is_range_path(&path);
+            // Ranges constructed with non-literals.
+            let source_map = self.tcx.sess.source_map();
+            let end_point = source_map.end_point(*span);
+
+            if let Ok(end_string) = source_map.span_to_snippet(end_point) {
+                end_string.ends_with("}") || end_string.ends_with(")")
+            } else {
+                false
             }
 
+        };
+
+        match expr.node {
+            // all built-in range literals but `..=` and `..`
+            // desugar to Structs, `..` desugars to its struct path
+            ExprKind::Struct(QPath::Resolved(None, ref path), _, _) |
+            ExprKind::Path(QPath::Resolved(None, ref path)) => {
+                return is_range_path(&path) && !is_range_struct_snippet(&expr.span);
+            }
+
+            // `..=` desugars into RangeInclusive::new(...)
             ExprKind::Call(ref func, _) => {
                 if let ExprKind::Path(QPath::TypeRelative(ref ty, ref segment)) = func.node {
                     if let TyKind::Path(QPath::Resolved(None, ref path)) = ty.node {
                         let calls_new = segment.ident.as_str() == "new";
 
-                        return is_range_path(&path) && calls_new;
+                        return is_range_path(&path) && calls_new &&
+                            !is_range_struct_snippet(&expr.span);
                     }
                 }
             }

src/test/ui/range/issue-54505-no-literals.fixed

@@ -0,0 +1,85 @@
+// Copyright 2018 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.
+
+// run-rustfix
+
+// Regression test for changes introduced while fixing #54505
+
+// This test uses non-literals for Ranges
+// (expecting no parens with borrow suggestion)
+
+use std::ops::RangeBounds;
+
+
+// take a reference to any built-in range
+fn take_range(_r: &impl RangeBounds<i8>) {}
+
+
+fn main() {
+    take_range(&std::ops::Range { start: 0, end: 1 });
+    //~^ ERROR mismatched types [E0308]
+    //~| HELP consider borrowing here
+    //~| SUGGESTION &std::ops::Range { start: 0, end: 1 }
+
+    take_range(&::std::ops::Range { start: 0, end: 1 });
+    //~^ ERROR mismatched types [E0308]
+    //~| HELP consider borrowing here
+    //~| SUGGESTION &::std::ops::Range { start: 0, end: 1 }
+
+    take_range(&std::ops::RangeFrom { start: 1 });
+    //~^ ERROR mismatched types [E0308]
+    //~| HELP consider borrowing here
+    //~| SUGGESTION &std::ops::RangeFrom { start: 1 }
+
+    take_range(&::std::ops::RangeFrom { start: 1 });
+    //~^ ERROR mismatched types [E0308]
+    //~| HELP consider borrowing here
+    //~| SUGGESTION &::std::ops::RangeFrom { start: 1 }
+
+    take_range(&std::ops::RangeFull {});
+    //~^ ERROR mismatched types [E0308]
+    //~| HELP consider borrowing here
+    //~| SUGGESTION &std::ops::RangeFull {}
+
+    take_range(&::std::ops::RangeFull {});
+    //~^ ERROR mismatched types [E0308]
+    //~| HELP consider borrowing here
+    //~| SUGGESTION &::std::ops::RangeFull {}
+
+    take_range(&std::ops::RangeInclusive::new(0, 1));
+    //~^ ERROR mismatched types [E0308]
+    //~| HELP consider borrowing here
+    //~| SUGGESTION &std::ops::RangeInclusive::new(0, 1)
+
+    take_range(&::std::ops::RangeInclusive::new(0, 1));
+    //~^ ERROR mismatched types [E0308]
+    //~| HELP consider borrowing here
+    //~| SUGGESTION &::std::ops::RangeInclusive::new(0, 1)
+
+    take_range(&std::ops::RangeTo { end: 5 });
+    //~^ ERROR mismatched types [E0308]
+    //~| HELP consider borrowing here
+    //~| SUGGESTION &std::ops::RangeTo { end: 5 }
+
+    take_range(&::std::ops::RangeTo { end: 5 });
+    //~^ ERROR mismatched types [E0308]
+    //~| HELP consider borrowing here
+    //~| SUGGESTION &::std::ops::RangeTo { end: 5 }
+
+    take_range(&std::ops::RangeToInclusive { end: 5 });
+    //~^ ERROR mismatched types [E0308]
+    //~| HELP consider borrowing here
+    //~| SUGGESTION &std::ops::RangeToInclusive { end: 5 }
+
+    take_range(&::std::ops::RangeToInclusive { end: 5 });
+    //~^ ERROR mismatched types [E0308]
+    //~| HELP consider borrowing here
+    //~| SUGGESTION &::std::ops::RangeToInclusive { end: 5 }
+}

src/test/ui/range/issue-54505-no-literals.stderr

@@ -0,0 +1,147 @@
+error[E0308]: mismatched types
+  --> $DIR/issue-54505-no-literals.rs:26:16
+   |
+LL |     take_range(std::ops::Range { start: 0, end: 1 });
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                |
+   |                expected reference, found struct `std::ops::Range`
+   |                help: consider borrowing here: `&std::ops::Range { start: 0, end: 1 }`
+   |
+   = note: expected type `&_`
+              found type `std::ops::Range<{integer}>`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-54505-no-literals.rs:31:16
+   |
+LL |     take_range(::std::ops::Range { start: 0, end: 1 });
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                |
+   |                expected reference, found struct `std::ops::Range`
+   |                help: consider borrowing here: `&::std::ops::Range { start: 0, end: 1 }`
+   |
+   = note: expected type `&_`
+              found type `std::ops::Range<{integer}>`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-54505-no-literals.rs:36:16
+   |
+LL |     take_range(std::ops::RangeFrom { start: 1 });
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                |
+   |                expected reference, found struct `std::ops::RangeFrom`
+   |                help: consider borrowing here: `&std::ops::RangeFrom { start: 1 }`
+   |
+   = note: expected type `&_`
+              found type `std::ops::RangeFrom<{integer}>`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-54505-no-literals.rs:41:16
+   |
+LL |     take_range(::std::ops::RangeFrom { start: 1 });
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                |
+   |                expected reference, found struct `std::ops::RangeFrom`
+   |                help: consider borrowing here: `&::std::ops::RangeFrom { start: 1 }`
+   |
+   = note: expected type `&_`
+              found type `std::ops::RangeFrom<{integer}>`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-54505-no-literals.rs:46:16
+   |
+LL |     take_range(std::ops::RangeFull {});
+   |                ^^^^^^^^^^^^^^^^^^^^^^
+   |                |
+   |                expected reference, found struct `std::ops::RangeFull`
+   |                help: consider borrowing here: `&std::ops::RangeFull {}`
+   |
+   = note: expected type `&_`
+              found type `std::ops::RangeFull`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-54505-no-literals.rs:51:16
+   |
+LL |     take_range(::std::ops::RangeFull {});
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^
+   |                |
+   |                expected reference, found struct `std::ops::RangeFull`
+   |                help: consider borrowing here: `&::std::ops::RangeFull {}`
+   |
+   = note: expected type `&_`
+              found type `std::ops::RangeFull`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-54505-no-literals.rs:56:16
+   |
+LL |     take_range(std::ops::RangeInclusive::new(0, 1));
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                |
+   |                expected reference, found struct `std::ops::RangeInclusive`
+   |                help: consider borrowing here: `&std::ops::RangeInclusive::new(0, 1)`
+   |
+   = note: expected type `&_`
+              found type `std::ops::RangeInclusive<{integer}>`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-54505-no-literals.rs:61:16
+   |
+LL |     take_range(::std::ops::RangeInclusive::new(0, 1));
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                |
+   |                expected reference, found struct `std::ops::RangeInclusive`
+   |                help: consider borrowing here: `&::std::ops::RangeInclusive::new(0, 1)`
+   |
+   = note: expected type `&_`
+              found type `std::ops::RangeInclusive<{integer}>`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-54505-no-literals.rs:66:16
+   |
+LL |     take_range(std::ops::RangeTo { end: 5 });
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                |
+   |                expected reference, found struct `std::ops::RangeTo`
+   |                help: consider borrowing here: `&std::ops::RangeTo { end: 5 }`
+   |
+   = note: expected type `&_`
+              found type `std::ops::RangeTo<{integer}>`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-54505-no-literals.rs:71:16
+   |
+LL |     take_range(::std::ops::RangeTo { end: 5 });
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                |
+   |                expected reference, found struct `std::ops::RangeTo`
+   |                help: consider borrowing here: `&::std::ops::RangeTo { end: 5 }`
+   |
+   = note: expected type `&_`
+              found type `std::ops::RangeTo<{integer}>`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-54505-no-literals.rs:76:16
+   |
+LL |     take_range(std::ops::RangeToInclusive { end: 5 });
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                |
+   |                expected reference, found struct `std::ops::RangeToInclusive`
+   |                help: consider borrowing here: `&std::ops::RangeToInclusive { end: 5 }`
+   |
+   = note: expected type `&_`
+              found type `std::ops::RangeToInclusive<{integer}>`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-54505-no-literals.rs:81:16
+   |
+LL |     take_range(::std::ops::RangeToInclusive { end: 5 });
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                |
+   |                expected reference, found struct `std::ops::RangeToInclusive`
+   |                help: consider borrowing here: `&::std::ops::RangeToInclusive { end: 5 }`
+   |
+   = note: expected type `&_`
+              found type `std::ops::RangeToInclusive<{integer}>`
+
+error: aborting due to 12 previous errors
+
+For more information about this error, try `rustc --explain E0308`.

src/test/ui/range/issue-54505-no-std.rs

@@ -8,9 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// run-rustfix
+// error-pattern: `#[panic_handler]` function required, but not found
-// error-pattern: error: `#[panic_handler]` function required, but not found
+// error-pattern: language item required, but not found: `eh_personality`
-// error-pattern: language item required, but not found: `panic_info`
 
 
 // Regression test for #54505 - range borrowing suggestion had

src/test/ui/range/issue-54505-no-std.stderr

@@ -0,0 +1,79 @@
+error: `#[panic_handler]` function required, but not found
+
+error: language item required, but not found: `eh_personality`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-54505-no-std.rs:31:16
+   |
+LL |     take_range(0..1);
+   |                ^^^^
+   |                |
+   |                expected reference, found struct `core::ops::Range`
+   |                help: consider borrowing here: `&(0..1)`
+   |
+   = note: expected type `&_`
+              found type `core::ops::Range<{integer}>`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-54505-no-std.rs:36:16
+   |
+LL |     take_range(1..);
+   |                ^^^
+   |                |
+   |                expected reference, found struct `core::ops::RangeFrom`
+   |                help: consider borrowing here: `&(1..)`
+   |
+   = note: expected type `&_`
+              found type `core::ops::RangeFrom<{integer}>`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-54505-no-std.rs:41:16
+   |
+LL |     take_range(..);
+   |                ^^
+   |                |
+   |                expected reference, found struct `core::ops::RangeFull`
+   |                help: consider borrowing here: `&(..)`
+   |
+   = note: expected type `&_`
+              found type `core::ops::RangeFull`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-54505-no-std.rs:46:16
+   |
+LL |     take_range(0..=1);
+   |                ^^^^^
+   |                |
+   |                expected reference, found struct `core::ops::RangeInclusive`
+   |                help: consider borrowing here: `&(0..=1)`
+   |
+   = note: expected type `&_`
+              found type `core::ops::RangeInclusive<{integer}>`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-54505-no-std.rs:51:16
+   |
+LL |     take_range(..5);
+   |                ^^^
+   |                |
+   |                expected reference, found struct `core::ops::RangeTo`
+   |                help: consider borrowing here: `&(..5)`
+   |
+   = note: expected type `&_`
+              found type `core::ops::RangeTo<{integer}>`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-54505-no-std.rs:56:16
+   |
+LL |     take_range(..=42);
+   |                ^^^^^
+   |                |
+   |                expected reference, found struct `core::ops::RangeToInclusive`
+   |                help: consider borrowing here: `&(..=42)`
+   |
+   = note: expected type `&_`
+              found type `core::ops::RangeToInclusive<{integer}>`
+
+error: aborting due to 8 previous errors
+
+For more information about this error, try `rustc --explain E0308`.