Defer ?Sized local binding error to get better suggestions

estebank · estebank · commit 40d36b1a6030 · 2020-10-23T13:01:15.000-07:00
diff --git a/compiler/rustc_typeck/src/check/expr.rs b/compiler/rustc_typeck/src/check/expr.rs
@@ -813,7 +813,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
         let rhs_ty = self.check_expr_coercable_to_type(&rhs, lhs_ty, Some(lhs));
 
-        self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
+        self.require_type_is_sized_deferred(lhs_ty, lhs.span, traits::AssignmentLhsSized);
 
         if lhs_ty.references_error() || rhs_ty.references_error() {
             self.tcx.ty_error()
diff --git a/compiler/rustc_typeck/src/check/gather_locals.rs b/compiler/rustc_typeck/src/check/gather_locals.rs
@@ -94,7 +94,11 @@ impl<'a, 'tcx> Visitor<'tcx> for GatherLocalsVisitor<'a, 'tcx> {
             let var_ty = self.assign(p.span, p.hir_id, None);
 
             if !self.fcx.tcx.features().unsized_locals {
-                self.fcx.require_type_is_sized(var_ty, p.span, traits::VariableType(p.hir_id));
+                self.fcx.require_type_is_sized_deferred(
+                    var_ty,
+                    p.span,
+                    traits::VariableType(p.hir_id),
+                );
             }
 
             debug!(
diff --git a/src/test/ui/error-codes/E0282.rs b/src/test/ui/error-codes/E0282.rs
@@ -1,3 +1,3 @@
 fn main() {
-    let x = "hello".chars().rev().collect(); //~ ERROR E0282
+    None; //~ ERROR E0282
 }
diff --git a/src/test/ui/error-codes/E0282.stderr b/src/test/ui/error-codes/E0282.stderr
@@ -1,13 +1,8 @@
 error[E0282]: type annotations needed
-  --> $DIR/E0282.rs:2:9
+  --> $DIR/E0282.rs:2:5
    |
-LL |     let x = "hello".chars().rev().collect();
-   |         ^ cannot infer type
-   |
-help: consider giving this binding a type
-   |
-LL |     let x: Type = "hello".chars().rev().collect();
-   |          ^^^^^^
+LL |     None;
+   |     ^^^^ cannot infer type for type parameter `T` declared on the enum `Option`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/for/for-loop-unconstrained-element-type.stderr b/src/test/ui/for/for-loop-unconstrained-element-type.stderr
@@ -2,7 +2,10 @@ error[E0282]: type annotations needed
   --> $DIR/for-loop-unconstrained-element-type.rs:8:14
    |
 LL |     for i in Vec::new() { }
-   |              ^^^^^^^^^^ the element type for this iterator is not specified
+   |              ^^^^^^^^--
+   |              |
+   |              the element type for this iterator is not specified
+   |              cannot infer type for type parameter `T`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issues/issue-12187-1.stderr b/src/test/ui/issues/issue-12187-1.stderr
@@ -1,10 +1,10 @@
 error[E0282]: type annotations needed for `&T`
-  --> $DIR/issue-12187-1.rs:6:10
+  --> $DIR/issue-12187-1.rs:6:14
    |
 LL |     let &v = new();
-   |          ^ cannot infer type
+   |              ^^^ cannot infer type for type parameter `T` declared on the function `new`
    |
-help: consider giving this binding the explicit type `&T`, with the type parameters specified
+help: consider giving this binding the explicit type `&T`, where the type parameter `T` is specified
    |
 LL |     let &v: &T = new();
    |           ^^^^
diff --git a/src/test/ui/issues/issue-12187-2.stderr b/src/test/ui/issues/issue-12187-2.stderr
@@ -1,10 +1,10 @@
 error[E0282]: type annotations needed for `&T`
-  --> $DIR/issue-12187-2.rs:6:10
+  --> $DIR/issue-12187-2.rs:6:14
    |
 LL |     let &v = new();
-   |          ^ cannot infer type
+   |              ^^^ cannot infer type for type parameter `T` declared on the function `new`
    |
-help: consider giving this binding the explicit type `&T`, with the type parameters specified
+help: consider giving this binding the explicit type `&T`, where the type parameter `T` is specified
    |
 LL |     let &v: &T = new();
    |           ^^^^
diff --git a/src/test/ui/issues/issue-24036.rs b/src/test/ui/issues/issue-24036.rs
@@ -6,11 +6,10 @@ fn closure_to_loc() {
 
 fn closure_from_match() {
     let x = match 1usize {
-        1 => |c| c + 1,
+        1 => |c| c + 1, //~ ERROR type annotations needed
         2 => |c| c - 1,
         _ => |c| c - 1
     };
-    //~^^^^ ERROR type annotations needed
 }
 
 fn main() { }
diff --git a/src/test/ui/issues/issue-24036.stderr b/src/test/ui/issues/issue-24036.stderr
@@ -11,11 +11,16 @@ LL |     x = |c| c + 1;
    = note: no two closures, even if identical, have the same type
    = help: consider boxing your closure and/or using it as a trait object
 
-error[E0282]: type annotations needed
-  --> $DIR/issue-24036.rs:9:15
+error[E0282]: type annotations needed for `fn(_) -> _`
+  --> $DIR/issue-24036.rs:9:18
    |
 LL |         1 => |c| c + 1,
-   |               ^ consider giving this closure parameter a type
+   |                  ^ cannot infer type
+   |
+help: consider giving this binding the explicit type `fn(_) -> _`, with the type parameters specified
+   |
+LL |     let x: fn(_) -> _ = match 1usize {
+   |          ^^^^^^^^^^^^
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/issues/issue-5883.stderr b/src/test/ui/issues/issue-5883.stderr
@@ -1,16 +1,3 @@
-error[E0277]: the size for values of type `(dyn A + 'static)` cannot be known at compilation time
-  --> $DIR/issue-5883.rs:7:15
-   |
-LL | fn new_struct(r: dyn A + 'static)
-   |               ^ doesn't have a size known at compile-time
-   |
-   = help: the trait `Sized` is not implemented for `(dyn A + 'static)`
-   = help: unsized locals are gated as an unstable feature
-help: function arguments must have a statically known size, borrowed types always have a known size
-   |
-LL | fn new_struct(r: &dyn A + 'static)
-   |                  ^
-
 error[E0277]: the size for values of type `(dyn A + 'static)` cannot be known at compilation time
   --> $DIR/issue-5883.rs:8:8
    |
@@ -24,6 +11,19 @@ LL |     Struct { r: r }
    = note: required because it appears within the type `Struct`
    = note: the return type of a function must have a statically known size
 
+error[E0277]: the size for values of type `(dyn A + 'static)` cannot be known at compilation time
+  --> $DIR/issue-5883.rs:7:15
+   |
+LL | fn new_struct(r: dyn A + 'static)
+   |               ^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `(dyn A + 'static)`
+   = help: unsized locals are gated as an unstable feature
+help: function arguments must have a statically known size, borrowed types always have a known size
+   |
+LL | fn new_struct(r: &dyn A + 'static)
+   |                  ^
+
 error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0277`.
diff --git a/src/test/ui/issues/issue-72690.stderr b/src/test/ui/issues/issue-72690.stderr
@@ -7,11 +7,14 @@ LL |     String::from("x".as_ref());
    = note: cannot satisfy `String: From<&_>`
    = note: required by `from`
 
-error[E0282]: type annotations needed
-  --> $DIR/issue-72690.rs:11:6
+error[E0283]: type annotations needed
+  --> $DIR/issue-72690.rs:11:9
    |
 LL |     |x| String::from("x".as_ref());
-   |      ^ consider giving this closure parameter a type
+   |         ^^^^^^^^^^^^ cannot infer type for struct `String`
+   |
+   = note: cannot satisfy `String: From<&_>`
+   = note: required by `from`
 
 error[E0283]: type annotations needed for `&T`
   --> $DIR/issue-72690.rs:15:17
@@ -91,5 +94,4 @@ LL |     let _: String = String::from("x");
 
 error: aborting due to 9 previous errors
 
-Some errors have detailed explanations: E0282, E0283.
-For more information about an error, try `rustc --explain E0282`.
+For more information about this error, try `rustc --explain E0283`.
diff --git a/src/test/ui/match/match-unresolved-one-arm.rs b/src/test/ui/match/match-unresolved-one-arm.rs
@@ -1,7 +1,7 @@
 fn foo<T>() -> T { panic!("Rocks for my pillow") }
 
 fn main() {
-    let x = match () { //~ ERROR type annotations needed
-        () => foo() // T here should be unresolved
+    let x = match () {
+        () => foo() //~ ERROR type annotations needed
     };
 }
diff --git a/src/test/ui/match/match-unresolved-one-arm.stderr b/src/test/ui/match/match-unresolved-one-arm.stderr
@@ -1,8 +1,8 @@
 error[E0282]: type annotations needed
-  --> $DIR/match-unresolved-one-arm.rs:4:9
+  --> $DIR/match-unresolved-one-arm.rs:5:15
    |
-LL |     let x = match () {
-   |         ^ cannot infer type
+LL |         () => foo()
+   |               ^^^ cannot infer type for type parameter `T` declared on the function `foo`
    |
 help: consider giving this binding a type
    |
diff --git a/src/test/ui/str/str-array-assignment.stderr b/src/test/ui/str/str-array-assignment.stderr
@@ -15,6 +15,16 @@ LL |   let u: &str = if true { s[..2] } else { s };
    |                           expected `&str`, found `str`
    |                           help: consider borrowing here: `&s[..2]`
 
+error[E0308]: mismatched types
+  --> $DIR/str-array-assignment.rs:9:17
+   |
+LL |   let w: &str = s[..2];
+   |          ----   ^^^^^^
+   |          |      |
+   |          |      expected `&str`, found `str`
+   |          |      help: consider borrowing here: `&s[..2]`
+   |          expected due to this
+
 error[E0277]: the size for values of type `str` cannot be known at compilation time
   --> $DIR/str-array-assignment.rs:7:7
    |
@@ -29,16 +39,6 @@ help: consider borrowing here
 LL |   let v = &s[..2];
    |           ^
 
-error[E0308]: mismatched types
-  --> $DIR/str-array-assignment.rs:9:17
-   |
-LL |   let w: &str = s[..2];
-   |          ----   ^^^^^^
-   |          |      |
-   |          |      expected `&str`, found `str`
-   |          |      help: consider borrowing here: `&s[..2]`
-   |          expected due to this
-
 error: aborting due to 4 previous errors
 
 Some errors have detailed explanations: E0277, E0308.
diff --git a/src/test/ui/str/str-mut-idx.rs b/src/test/ui/str/str-mut-idx.rs
@@ -1,17 +1,13 @@
 fn bot<T>() -> T { loop {} }
 
 fn mutate(s: &mut str) {
-    s[1..2] = bot();
-    //~^ ERROR the size for values of type
-    //~| ERROR the size for values of type
-    s[1usize] = bot();
-    //~^ ERROR the type `str` cannot be indexed by `usize`
-    s.get_mut(1);
-    //~^ ERROR the type `str` cannot be indexed by `{integer}`
-    s.get_unchecked_mut(1);
-    //~^ ERROR the type `str` cannot be indexed by `{integer}`
-    s['c'];
-    //~^ ERROR the type `str` cannot be indexed by `char`
+    s[1..2] = bot(); //~ ERROR the size for values of type
+    // A second error would happen due to `s[1..2]` but it isn't emitted because it is delayed and
+    // there are already other errors being emitted.
+    s[1usize] = bot(); //~ ERROR the type `str` cannot be indexed by `usize`
+    s.get_mut(1); //~ ERROR the type `str` cannot be indexed by `{integer}`
+    s.get_unchecked_mut(1); //~ ERROR the type `str` cannot be indexed by `{integer}`
+    s['c']; //~ ERROR the type `str` cannot be indexed by `char`
 }
 
 pub fn main() {}
diff --git a/src/test/ui/str/str-mut-idx.stderr b/src/test/ui/str/str-mut-idx.stderr
@@ -13,15 +13,6 @@ help: consider relaxing the implicit `Sized` restriction
 LL | fn bot<T: ?Sized>() -> T { loop {} }
    |         ^^^^^^^^
 
-error[E0277]: the size for values of type `str` cannot be known at compilation time
-  --> $DIR/str-mut-idx.rs:4:5
-   |
-LL |     s[1..2] = bot();
-   |     ^^^^^^^ doesn't have a size known at compile-time
-   |
-   = help: the trait `Sized` is not implemented for `str`
-   = note: the left-hand-side of an assignment must have a statically known size
-
 error[E0277]: the type `str` cannot be indexed by `usize`
   --> $DIR/str-mut-idx.rs:7:5
    |
@@ -32,7 +23,7 @@ LL |     s[1usize] = bot();
    = note: required because of the requirements on the impl of `Index<usize>` for `str`
 
 error[E0277]: the type `str` cannot be indexed by `{integer}`
-  --> $DIR/str-mut-idx.rs:9:15
+  --> $DIR/str-mut-idx.rs:8:15
    |
 LL |     s.get_mut(1);
    |               ^ string indices are ranges of `usize`
@@ -42,7 +33,7 @@ LL |     s.get_mut(1);
            for more information, see chapter 8 in The Book: <https://doc.rust-lang.org/book/ch08-02-strings.html#indexing-into-strings>
 
 error[E0277]: the type `str` cannot be indexed by `{integer}`
-  --> $DIR/str-mut-idx.rs:11:25
+  --> $DIR/str-mut-idx.rs:9:25
    |
 LL |     s.get_unchecked_mut(1);
    |                         ^ string indices are ranges of `usize`
@@ -52,14 +43,14 @@ LL |     s.get_unchecked_mut(1);
            for more information, see chapter 8 in The Book: <https://doc.rust-lang.org/book/ch08-02-strings.html#indexing-into-strings>
 
 error[E0277]: the type `str` cannot be indexed by `char`
-  --> $DIR/str-mut-idx.rs:13:5
+  --> $DIR/str-mut-idx.rs:10:5
    |
 LL |     s['c'];
    |     ^^^^^^ string indices are ranges of `usize`
    |
    = help: the trait `SliceIndex<str>` is not implemented for `char`
    = note: required because of the requirements on the impl of `Index<char>` for `str`
 
-error: aborting due to 6 previous errors
+error: aborting due to 5 previous errors
 
 For more information about this error, try `rustc --explain E0277`.
diff --git a/src/test/ui/suggestions/appropriate-type-param-turbofish.rs b/src/test/ui/suggestions/appropriate-type-param-turbofish.rs
@@ -21,6 +21,18 @@ mod b {
     }
 }
 
+mod c {
+    fn foo() {
+        let _x = vec![1, 2, 3].into_iter().collect(); //~ ERROR type annotations needed
+    }
+    fn bar() {
+        let _x = vec!["a", "b", "c"].into_iter().collect(); //~ ERROR type annotations needed
+    }
+    fn qux() {
+        let _x = vec!['a', 'b', 'c'].into_iter().collect(); //~ ERROR type annotations needed
+    }
+}
+
 trait T: Sized {
     fn new() -> Self;
 }
diff --git a/src/test/ui/suggestions/appropriate-type-param-turbofish.stderr b/src/test/ui/suggestions/appropriate-type-param-turbofish.stderr
diff --git a/src/test/ui/unsized6.rs b/src/test/ui/unsized6.rs
diff --git a/src/test/ui/unsized6.stderr b/src/test/ui/unsized6.stderr
diff --git a/src/test/ui/unsized8.rs b/src/test/ui/unsized8.rs
diff --git a/src/test/ui/unsized8.stderr b/src/test/ui/unsized8.stderr

Original file line number	Diff line number	Diff line change
`@@ -1,3 +1,3 @@`
`1`	`1`	`fn main() {`
`2`		`- let x = "hello".chars().rev().collect(); //~ ERROR E0282`
	`2`	`+ None; //~ ERROR E0282`
`3`	`3`	`}`
Original file line number	Diff line number	Diff line change
`@@ -1,10 +1,10 @@`
`1`	`1`	error[E0282]: type annotations needed for `&T`
`2`		`- --> $DIR/issue-12187-1.rs:6:10`
	`2`	`+ --> $DIR/issue-12187-1.rs:6:14`
`3`	`3`	`\|`
`4`	`4`	`LL \| let &v = new();`
`5`		`- \| ^ cannot infer type`
	`5`	+ \| ^^^ cannot infer type for type parameter `T` declared on the function `new`
`6`	`6`	`\|`
`7`		-help: consider giving this binding the explicit type `&T`, with the type parameters specified
	`7`	+help: consider giving this binding the explicit type `&T`, where the type parameter `T` is specified
`8`	`8`	`\|`
`9`	`9`	`LL \| let &v: &T = new();`
`10`	`10`	`\| ^^^^`
Original file line number	Diff line number	Diff line change
`@@ -1,10 +1,10 @@`
`1`	`1`	error[E0282]: type annotations needed for `&T`
`2`		`- --> $DIR/issue-12187-2.rs:6:10`
	`2`	`+ --> $DIR/issue-12187-2.rs:6:14`
`3`	`3`	`\|`
`4`	`4`	`LL \| let &v = new();`
`5`		`- \| ^ cannot infer type`
	`5`	+ \| ^^^ cannot infer type for type parameter `T` declared on the function `new`
`6`	`6`	`\|`
`7`		-help: consider giving this binding the explicit type `&T`, with the type parameters specified
	`7`	+help: consider giving this binding the explicit type `&T`, where the type parameter `T` is specified
`8`	`8`	`\|`
`9`	`9`	`LL \| let &v: &T = new();`
`10`	`10`	`\| ^^^^`