Suggest dereferencing LHS of assignment operator #93575

compiler-errors · 2022-02-02T08:33:09Z

Putting this diagnostic up for consideration, since I was dissatisfied with the unhelpful error message after I fixed the bug in #93574.

This suggestion isn't always correct, but it seems like many of our diagnostics are not, and it should be correct in simple cases. My only wish is that there were an FnCtxt::autoderef that only suggested DerefMut implementations so we can get the mutability correct...

Also I had to split the check_expr_coercable_to_type into check_expr_with_hint and demand_coerce_diag so I could delay emitting the coercion error, but that's basically what the former was doing in the first place. Let me know if I should refactor some of this logic into a helper fn.

rust-highfive · 2022-02-02T08:33:12Z

r? @oli-obk

(rust-highfive has picked a reviewer for you, use r? to override)

rust-log-analyzer · 2022-02-02T08:51:21Z

The job x86_64-gnu-llvm-12 failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

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---
5    |     - ^
6    |     |
7    |     cannot assign to this expression
+    |
+ help: consider dereferencing here to assign a value to the left-hand side
+ LL -     1 = 2;
+ LL +     1 = 2;
+    | 
8 
---
To only update this specific test, also pass `--test-args async-await/issue-73741-type-err.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/async-await/issue-73741-type-err.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/async-await/issue-73741-type-err" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--edition=2018" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/async-await/issue-73741-type-err/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error[E0070]: invalid left-hand side of assignment
   |
   |
LL |     1 = 2; //~ ERROR invalid left-hand side
   |     - ^
   |     cannot assign to this expression
   |
   |
help: consider dereferencing here to assign a value to the left-hand side
   |
LL -     1 = 2; //~ ERROR invalid left-hand side
LL +     1 = 2; //~ ERROR invalid left-hand side

error: aborting due to previous error

For more information about this error, try `rustc --explain E0070`.
---
5    |     - ^
6    |     |
7    |     cannot assign to this expression
+    |
+ help: consider dereferencing here to assign a value to the left-hand side
+ LL -     1 = 2;
+ LL +     1 = 2;
+    | 
8 
8 
9 error[E0067]: invalid left-hand side of assignment

21    |      -     ^
22    |      |
23    |      cannot assign to this expression
23    |      cannot assign to this expression
+    |
+ help: consider dereferencing here to assign a value to the left-hand side
+    |
+ LL -     (1, 2) = (3, 4);
+ LL +     (1, 2) = (3, 4);
24 
24 
25 error[E0070]: invalid left-hand side of assignment

29    |         -  ^
30    |         |
31    |         cannot assign to this expression
31    |         cannot assign to this expression
+    |
+ help: consider dereferencing here to assign a value to the left-hand side
+    |
+ LL -     (1, 2) = (3, 4);
+ LL +     (1, 2) = (3, 4);
32 
32 
33 error[E0070]: invalid left-hand side of assignment

37    |     ---- ^
38    |     |
Some tests failed in compiletest suite=ui mode=ui host=x86_64-unknown-linux-gnu target=x86_64-unknown-linux-gnu
Some tests failed in compiletest suite=ui mode=ui host=x86_64-unknown-linux-gnu target=x86_64-unknown-linux-gnu
39    |     cannot assign to this expression
+    |
+ help: consider dereferencing here to assign a value to the left-hand side
+ LL -     None = Some(3);
+ LL +     None = Some(3);
+    | 
40 
---
To only update this specific test, also pass `--test-args destructuring-assignment/bad-expr-lhs.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/destructuring-assignment/bad-expr-lhs.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/destructuring-assignment/bad-expr-lhs" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/destructuring-assignment/bad-expr-lhs/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error[E0070]: invalid left-hand side of assignment
  --> /checkout/src/test/ui/destructuring-assignment/bad-expr-lhs.rs:2:7
   |
LL |     1 = 2; //~ ERROR invalid left-hand side of assignment
   |     - ^
   |     cannot assign to this expression
   |
   |
help: consider dereferencing here to assign a value to the left-hand side
   |
LL -     1 = 2; //~ ERROR invalid left-hand side of assignment
LL +     1 = 2; //~ ERROR invalid left-hand side of assignment


error[E0067]: invalid left-hand side of assignment
  --> /checkout/src/test/ui/destructuring-assignment/bad-expr-lhs.rs:3:7
   |
LL |     1 += 2; //~ ERROR invalid left-hand side of assignment
   |     - ^^
   |     cannot assign to this expression


error[E0070]: invalid left-hand side of assignment
  --> /checkout/src/test/ui/destructuring-assignment/bad-expr-lhs.rs:4:12
   |
LL |     (1, 2) = (3, 4);
   |      -     ^
   |      cannot assign to this expression
   |
   |
help: consider dereferencing here to assign a value to the left-hand side
   |
LL -     (1, 2) = (3, 4);
LL +     (1, 2) = (3, 4);


error[E0070]: invalid left-hand side of assignment
  --> /checkout/src/test/ui/destructuring-assignment/bad-expr-lhs.rs:4:12
   |
LL |     (1, 2) = (3, 4);
   |         -  ^
   |         cannot assign to this expression
   |
   |
help: consider dereferencing here to assign a value to the left-hand side
   |
LL -     (1, 2) = (3, 4);
LL +     (1, 2) = (3, 4);


error[E0070]: invalid left-hand side of assignment
  --> /checkout/src/test/ui/destructuring-assignment/bad-expr-lhs.rs:8:10
   |
LL |     None = Some(3); //~ ERROR invalid left-hand side of assignment
   |     ---- ^
   |     cannot assign to this expression
   |
   |
help: consider dereferencing here to assign a value to the left-hand side
   |
LL -     None = Some(3); //~ ERROR invalid left-hand side of assignment
LL +     None = Some(3); //~ ERROR invalid left-hand side of assignment

error: aborting due to 5 previous errors

Some errors have detailed explanations: E0067, E0070.
---
22    |      -      ^
23    |      |
24    |      cannot assign to this expression
+    |
+ help: consider dereferencing here to assign a value to the left-hand side
+    |
+ LL -     (C, ..) = (0,1);
+ LL +     (C, ..) = (0,1);
25 
26 error[E0308]: mismatched types
27   --> $DIR/tuple_destructure_fail.rs:8:5

---
To only update this specific test, also pass `--test-args destructuring-assignment/tuple_destructure_fail.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/destructuring-assignment/tuple_destructure_fail.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/destructuring-assignment/tuple_destructure_fail" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/destructuring-assignment/tuple_destructure_fail/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error: `..` can only be used once per tuple pattern
  --> /checkout/src/test/ui/destructuring-assignment/tuple_destructure_fail.rs:5:16
   |
LL |     (a, .., b, ..) = (0, 1); //~ ERROR `..` can only be used once per tuple pattern
   |         --     ^^ can only be used once per tuple pattern
   |         previously used here

error[E0308]: mismatched types
  --> /checkout/src/test/ui/destructuring-assignment/tuple_destructure_fail.rs:6:5
  --> /checkout/src/test/ui/destructuring-assignment/tuple_destructure_fail.rs:6:5
   |
LL |     (a, a, b) = (1, 2); //~ ERROR mismatched types
   |     ^^^^^^^^^ expected a tuple with 2 elements, found one with 3 elements
   |
   = note: expected type `({integer}, {integer})`
             found tuple `(_, _, _)`

error[E0070]: invalid left-hand side of assignment
  --> /checkout/src/test/ui/destructuring-assignment/tuple_destructure_fail.rs:7:13
   |
LL |     (C, ..) = (0,1); //~ ERROR invalid left-hand side of assignment
   |      -      ^
   |      cannot assign to this expression
   |
   |
help: consider dereferencing here to assign a value to the left-hand side
   |
LL -     (C, ..) = (0,1); //~ ERROR invalid left-hand side of assignment
LL +     (C, ..) = (0,1); //~ ERROR invalid left-hand side of assignment

error[E0308]: mismatched types
  --> /checkout/src/test/ui/destructuring-assignment/tuple_destructure_fail.rs:8:5
   |
   |
LL |     (_,) = (1, 2); //~ ERROR mismatched types
   |     ^^^^ expected a tuple with 2 elements, found one with 1 element
   |
   = note: expected type `({integer}, {integer})`
             found tuple `(_,)`
error: aborting due to 4 previous errors

Some errors have detailed explanations: E0070, E0308.
For more information about an error, try `rustc --explain E0070`.
---
75    |     ------ ^
76    |     |
77    |     cannot assign to this expression
+    |
+ help: consider dereferencing here to assign a value to the left-hand side
+    |
+ LL -     test() = TupleStruct(0, 0);
+ LL +     test() = TupleStruct(0, 0);
78 
78 
79 error[E0070]: invalid left-hand side of assignment
80   --> $DIR/tuple_struct_destructure_fail.rs:40:14
83    |     -------- ^
84    |     |
85    |     cannot assign to this expression
+    |
+    |
+ help: consider dereferencing here to assign a value to the left-hand side
+    |
+ LL -     (test)() = TupleStruct(0, 0);
+ LL +     (test)() = TupleStruct(0, 0);
86 
86 
87 error[E0070]: invalid left-hand side of assignment
88   --> $DIR/tuple_struct_destructure_fail.rs:42:38
91    |     -------------------------------- ^
92    |     |
93    |     cannot assign to this expression
+    |
+    |
+ help: consider dereferencing here to assign a value to the left-hand side
+    |
+ LL -     <Alias::<isize> as Test>::test() = TupleStruct(0, 0);
+ LL +     <Alias::<isize> as Test>::test() = TupleStruct(0, 0);
94 
95 error: aborting due to 9 previous errors
96 

---
To only update this specific test, also pass `--test-args destructuring-assignment/tuple_struct_destructure_fail.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/destructuring-assignment/tuple_struct_destructure_fail.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/destructuring-assignment/tuple_struct_destructure_fail" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/destructuring-assignment/tuple_struct_destructure_fail/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error: `..` can only be used once per tuple struct or variant pattern
  --> /checkout/src/test/ui/destructuring-assignment/tuple_struct_destructure_fail.rs:23:27
   |
LL |     TupleStruct(a, .., b, ..) = TupleStruct(0, 1);
   |                    --     ^^ can only be used once per tuple struct or variant pattern
   |                    previously used here


error: `..` can only be used once per tuple struct or variant pattern
  --> /checkout/src/test/ui/destructuring-assignment/tuple_struct_destructure_fail.rs:25:35
   |
LL |     Enum::SingleVariant(a, .., b, ..) = Enum::SingleVariant(0, 1);
   |                            --     ^^ can only be used once per tuple struct or variant pattern
   |                            previously used here


error[E0023]: this pattern has 3 fields, but the corresponding tuple struct has 2 fields
  --> /checkout/src/test/ui/destructuring-assignment/tuple_struct_destructure_fail.rs:28:17
   |
LL | struct TupleStruct<S, T>(S, T);
   |                          -  - tuple struct has 2 fields
...
LL |     TupleStruct(a, a, b) = TupleStruct(1, 2);
   |                 ^  ^  ^ expected 2 fields, found 3

error[E0023]: this pattern has 1 field, but the corresponding tuple struct has 2 fields
  --> /checkout/src/test/ui/destructuring-assignment/tuple_struct_destructure_fail.rs:30:17
   |
LL | struct TupleStruct<S, T>(S, T);
   |                          -  - tuple struct has 2 fields
...
LL |     TupleStruct(_) = TupleStruct(1, 2);
   |                 ^ expected 2 fields, found 1
   |
help: use `_` to explicitly ignore each field
   |
LL |     TupleStruct(_, _) = TupleStruct(1, 2);
help: use `..` to ignore all fields
   |
   |
LL |     TupleStruct(..) = TupleStruct(1, 2);


error[E0023]: this pattern has 3 fields, but the corresponding tuple variant has 2 fields
  --> /checkout/src/test/ui/destructuring-assignment/tuple_struct_destructure_fail.rs:32:25
   |
LL |     SingleVariant(S, T)
   |                   -  - tuple variant has 2 fields
...
LL |     Enum::SingleVariant(a, a, b) = Enum::SingleVariant(1, 2);
   |                         ^  ^  ^ expected 2 fields, found 3

error[E0023]: this pattern has 1 field, but the corresponding tuple variant has 2 fields
  --> /checkout/src/test/ui/destructuring-assignment/tuple_struct_destructure_fail.rs:34:25
   |
LL |     SingleVariant(S, T)
   |                   -  - tuple variant has 2 fields
...
LL |     Enum::SingleVariant(_) = Enum::SingleVariant(1, 2);
   |                         ^ expected 2 fields, found 1
   |
help: use `_` to explicitly ignore each field
   |
LL |     Enum::SingleVariant(_, _) = Enum::SingleVariant(1, 2);
help: use `..` to ignore all fields
   |
   |
LL |     Enum::SingleVariant(..) = Enum::SingleVariant(1, 2);


error[E0070]: invalid left-hand side of assignment
  --> /checkout/src/test/ui/destructuring-assignment/tuple_struct_destructure_fail.rs:38:12
   |
LL |     test() = TupleStruct(0, 0);
   |     ------ ^
   |     cannot assign to this expression
   |
   |
help: consider dereferencing here to assign a value to the left-hand side
   |
LL -     test() = TupleStruct(0, 0);
LL +     test() = TupleStruct(0, 0);


error[E0070]: invalid left-hand side of assignment
  --> /checkout/src/test/ui/destructuring-assignment/tuple_struct_destructure_fail.rs:40:14
   |
LL |     (test)() = TupleStruct(0, 0);
   |     -------- ^
   |     cannot assign to this expression
   |
   |
help: consider dereferencing here to assign a value to the left-hand side
   |
LL -     (test)() = TupleStruct(0, 0);
LL +     (test)() = TupleStruct(0, 0);


error[E0070]: invalid left-hand side of assignment
  --> /checkout/src/test/ui/destructuring-assignment/tuple_struct_destructure_fail.rs:42:38
   |
LL |     <Alias::<isize> as Test>::test() = TupleStruct(0, 0);
   |     -------------------------------- ^
   |     cannot assign to this expression
   |
   |
help: consider dereferencing here to assign a value to the left-hand side
   |
LL -     <Alias::<isize> as Test>::test() = TupleStruct(0, 0);
LL +     <Alias::<isize> as Test>::test() = TupleStruct(0, 0);

error: aborting due to 9 previous errors

Some errors have detailed explanations: E0023, E0070.
---
5    |     ---------- ^
6    |     |
7    |     cannot assign to this expression
+    |
+ help: consider dereferencing here to assign a value to the left-hand side
+ LL -     SOME_CONST = 14;
+ LL +     SOME_CONST = 14;
+    | 
8 
8 
9 error[E0070]: invalid left-hand side of assignment
10   --> $DIR/E0070.rs:7:7
13    |     - ^
14    |     |
15    |     cannot assign to this expression
+    |
+    |
+ help: consider dereferencing here to assign a value to the left-hand side
+ LL -     1 = 3;
+ LL +     1 = 3;
+    | 
16 
16 
17 error[E0070]: invalid left-hand side of assignment
18   --> $DIR/E0070.rs:8:23

The actual stderr differed from the expected stderr.
Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/error-codes/E0070/E0070.stderr
To update references, rerun the tests and pass the `--bless` flag
To update references, rerun the tests and pass the `--bless` flag
To only update this specific test, also pass `--test-args error-codes/E0070.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/error-codes/E0070.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/error-codes/E0070" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/error-codes/E0070/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error[E0070]: invalid left-hand side of assignment
   |
   |
LL |     SOME_CONST = 14; //~ ERROR E0070
   |     ---------- ^
   |     cannot assign to this expression
   |
   |
help: consider dereferencing here to assign a value to the left-hand side
   |
LL -     SOME_CONST = 14; //~ ERROR E0070
LL +     SOME_CONST = 14; //~ ERROR E0070


error[E0070]: invalid left-hand side of assignment
   |
   |
LL |     1 = 3; //~ ERROR E0070
   |     - ^
   |     cannot assign to this expression
   |
   |
help: consider dereferencing here to assign a value to the left-hand side
   |
LL -     1 = 3; //~ ERROR E0070
LL +     1 = 3; //~ ERROR E0070


error[E0070]: invalid left-hand side of assignment
   |
   |
LL |     some_other_func() = 4; //~ ERROR E0070
   |     ----------------- ^
   |     cannot assign to this expression

error: aborting due to 3 previous errors

---
diff of stderr:

11    |     in this macro invocation
12    |
13    = note: this error originates in the macro `not_a_place` (in Nightly builds, run with -Z macro-backtrace for more info)
+ help: consider dereferencing here to assign a value to the left-hand side
+    |
+ LL -     not_a_place!(99);
+ LL +     not_a_place!(99);
14 
14 
15 error[E0067]: invalid left-hand side of assignment


The actual stderr differed from the expected stderr.
Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/issues/issue-26093/issue-26093.stderr
Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/issues/issue-26093/issue-26093.stderr
To update references, rerun the tests and pass the `--bless` flag
To only update this specific test, also pass `--test-args issues/issue-26093.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/issues/issue-26093.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/issues/issue-26093" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/issues/issue-26093/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error[E0070]: invalid left-hand side of assignment
   |
   |
LL |         $thing = 42;
...
...
LL |     not_a_place!(99);
   |     |            |
   |     |            cannot assign to this expression
   |     in this macro invocation
   |
   |
   = note: this error originates in the macro `not_a_place` (in Nightly builds, run with -Z macro-backtrace for more info)
help: consider dereferencing here to assign a value to the left-hand side
   |
LL -     not_a_place!(99);
LL +     not_a_place!(99);


error[E0067]: invalid left-hand side of assignment
   |
   |
LL |         $thing += 42;
...
...
LL |     not_a_place!(99);
   |     |            |
   |     |            cannot assign to this expression
   |     in this macro invocation
   |
---

---- [ui] ui/issues/issue-53348.rs stdout ----
diff of stderr:

6 LL |     for i in v {
7 LL |         a = *i.to_string();
8    |             ^^^^^^^^^^^^^^ expected struct `String`, found `str`
+    |
+ help: consider dereferencing here to assign a value to the left-hand side
+    |
+ LL |         *a = *i.to_string();
9 
10 error: aborting due to previous error
11 

---
To only update this specific test, also pass `--test-args issues/issue-53348.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/issues/issue-53348.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/issues/issue-53348" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/issues/issue-53348/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error[E0308]: mismatched types
  --> /checkout/src/test/ui/issues/issue-53348.rs:10:13
   |
LL |     let mut a = String::new(); //~ NOTE expected due to this value
LL |     for i in v {
LL |     for i in v {
LL |         a = *i.to_string();
   |             ^^^^^^^^^^^^^^ expected struct `String`, found `str`
   |
help: consider dereferencing here to assign a value to the left-hand side
   |
LL |         *a = *i.to_string();

error: aborting due to previous error

For more information about this error, try `rustc --explain E0308`.
---
45    |             -  ^
46    |             |
47    |             cannot assign to this expression
+    |
+ help: consider dereferencing here to assign a value to the left-hand side
+    |
+ LL -     if Some(3) = foo {}
+ LL +     if Some(3) = foo {}
48 
49 error[E0308]: mismatched types
50   --> $DIR/if-let-typo.rs:8:8

---
To only update this specific test, also pass `--test-args suggestions/if-let-typo.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/suggestions/if-let-typo.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/suggestions/if-let-typo" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/suggestions/if-let-typo/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error[E0425]: cannot find value `x` in this scope
  --> /checkout/src/test/ui/suggestions/if-let-typo.rs:4:13
   |
LL |     if Some(x) = foo {} //~ ERROR cannot find value `x` in this scope
   |
help: you might have meant to use pattern matching
   |
   |
LL |     if let Some(x) = foo {} //~ ERROR cannot find value `x` in this scope

error[E0425]: cannot find value `x` in this scope
  --> /checkout/src/test/ui/suggestions/if-let-typo.rs:10:8
   |
   |
LL |     if x = 5 {}  //~ ERROR cannot find value `x` in this scope
   |
help: you might have meant to use pattern matching
   |
   |
LL |     if let x = 5 {}  //~ ERROR cannot find value `x` in this scope

error[E0308]: mismatched types
  --> /checkout/src/test/ui/suggestions/if-let-typo.rs:4:8
   |
   |
LL |     if Some(x) = foo {} //~ ERROR cannot find value `x` in this scope
   |        ^^^^^^^^^^^^^ expected `bool`, found `()`
error[E0308]: mismatched types
  --> /checkout/src/test/ui/suggestions/if-let-typo.rs:6:8
   |
   |
LL |     if Some(foo) = bar {} //~ ERROR mismatched types
   |        ^^^^^^^^^^^^^^^ expected `bool`, found `()`
error[E0308]: mismatched types
  --> /checkout/src/test/ui/suggestions/if-let-typo.rs:7:8
   |
   |
LL |     if 3 = foo {} //~ ERROR mismatched types
   |        ^^^^^^^ expected `bool`, found `()`

error[E0070]: invalid left-hand side of assignment
   |
   |
LL |     if Some(3) = foo {} //~ ERROR mismatched types
   |             -  ^
   |             cannot assign to this expression
   |
   |
help: consider dereferencing here to assign a value to the left-hand side
   |
LL -     if Some(3) = foo {} //~ ERROR mismatched types
LL +     if Some(3) = foo {} //~ ERROR mismatched types

error[E0308]: mismatched types
  --> /checkout/src/test/ui/suggestions/if-let-typo.rs:8:8
   |
   |
LL |     if Some(3) = foo {} //~ ERROR mismatched types
   |        ^^^^^^^^^^^^^ expected `bool`, found `()`
error: aborting due to 7 previous errors

Some errors have detailed explanations: E0070, E0308, E0425.
For more information about an error, try `rustc --explain E0070`.
---
---- [ui] ui/suggestions/mut-ref-reassignment.rs stdout ----
diff of stderr:

12    |
13 LL |     *opt = None;
14    |     +
+ help: consider dereferencing here to assign a value to the left-hand side
+    |
+ LL |     *opt = None;
15 
16 error[E0308]: mismatched types
17   --> $DIR/mut-ref-reassignment.rs:6:11


35    = note: expected mutable reference `&mut Option<String>`
36                            found enum `Option<String>`
37 help: consider dereferencing here to assign to the mutable borrowed piece of memory
+    |
+ LL |     *opt = Some(String::new())
+    |     +
+ help: consider dereferencing here to assign a value to the left-hand side
38    |
39 LL |     *opt = Some(String::new())


The actual stderr differed from the expected stderr.
Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/suggestions/mut-ref-reassignment/mut-ref-reassignment.stderr
Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/suggestions/mut-ref-reassignment/mut-ref-reassignment.stderr
To update references, rerun the tests and pass the `--bless` flag
To only update this specific test, also pass `--test-args suggestions/mut-ref-reassignment.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/suggestions/mut-ref-reassignment.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/suggestions/mut-ref-reassignment" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/suggestions/mut-ref-reassignment/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error[E0308]: mismatched types
  --> /checkout/src/test/ui/suggestions/mut-ref-reassignment.rs:2:11
   |
LL | fn suggestion(opt: &mut Option<String>) {
   |                    ------------------- expected due to this parameter type
LL |     opt = None; //~ ERROR mismatched types
   |
   = note: expected mutable reference `&mut Option<String>`
                           found enum `Option<_>`
                           found enum `Option<_>`
help: consider dereferencing here to assign to the mutable borrowed piece of memory
   |
LL |     *opt = None; //~ ERROR mismatched types
   |     +
help: consider dereferencing here to assign a value to the left-hand side
   |
LL |     *opt = None; //~ ERROR mismatched types

error[E0308]: mismatched types
  --> /checkout/src/test/ui/suggestions/mut-ref-reassignment.rs:6:11
   |
   |
LL | fn no_suggestion(opt: &mut Result<String, ()>) {
   |                       ----------------------- expected due to this parameter type
LL |     opt = None //~ ERROR mismatched types
   |
   = note: expected mutable reference `&mut Result<String, ()>`
                           found enum `Option<_>`


error[E0308]: mismatched types
  --> /checkout/src/test/ui/suggestions/mut-ref-reassignment.rs:10:11
   |
LL | fn suggestion2(opt: &mut Option<String>) {
   |                     ------------------- expected due to this parameter type
LL |     opt = Some(String::new())//~ ERROR mismatched types
   |
   = note: expected mutable reference `&mut Option<String>`
                           found enum `Option<String>`
                           found enum `Option<String>`
help: consider dereferencing here to assign to the mutable borrowed piece of memory
   |
LL |     *opt = Some(String::new())//~ ERROR mismatched types
   |     +
help: consider dereferencing here to assign a value to the left-hand side
   |
LL |     *opt = Some(String::new())//~ ERROR mismatched types

error[E0308]: mismatched types
  --> /checkout/src/test/ui/suggestions/mut-ref-reassignment.rs:14:11
   |
   |
LL | fn no_suggestion2(opt: &mut Option<String>) {
   |                        ------------------- expected due to this parameter type
LL |     opt = Some(42)//~ ERROR mismatched types
   |
   = note: expected mutable reference `&mut Option<String>`
                           found enum `Option<{integer}>`

---

38    |
39 LL |     while let Some(3) = foo {}
40    |           +++
+ help: consider dereferencing here to assign a value to the left-hand side
+    |
+ LL -     while Some(3) = foo {}
+ LL +     while Some(3) = foo {}
41 
42 error: aborting due to 4 previous errors
43 

---
To only update this specific test, also pass `--test-args suggestions/while-let-typo.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/suggestions/while-let-typo.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/suggestions/while-let-typo" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/suggestions/while-let-typo/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error[E0425]: cannot find value `x` in this scope
  --> /checkout/src/test/ui/suggestions/while-let-typo.rs:4:16
   |
LL |     while Some(x) = foo {} //~ ERROR cannot find value `x` in this scope
   |
help: you might have meant to use pattern matching
   |
   |
LL |     while let Some(x) = foo {} //~ ERROR cannot find value `x` in this scope

error[E0425]: cannot find value `x` in this scope
  --> /checkout/src/test/ui/suggestions/while-let-typo.rs:8:11
   |
   |
LL |     while x = 5 {} //~ ERROR cannot find value `x` in this scope
   |
help: you might have meant to use pattern matching
   |
   |
LL |     while let x = 5 {} //~ ERROR cannot find value `x` in this scope

error[E0308]: mismatched types
  --> /checkout/src/test/ui/suggestions/while-let-typo.rs:6:11
   |
   |
LL |     while 3 = foo {} //~ ERROR mismatched types
   |           ^^^^^^^ expected `bool`, found `()`

error[E0070]: invalid left-hand side of assignment
   |
   |
LL |     while Some(3) = foo {} //~ ERROR invalid left-hand side of assignment
   |                -  ^
   |                cannot assign to this expression
   |
   |
help: you might have meant to use pattern destructuring
   |
LL |     while let Some(3) = foo {} //~ ERROR invalid left-hand side of assignment
   |           +++
help: consider dereferencing here to assign a value to the left-hand side
   |
LL -     while Some(3) = foo {} //~ ERROR invalid left-hand side of assignment
LL +     while Some(3) = foo {} //~ ERROR invalid left-hand side of assignment

error: aborting due to 4 previous errors

Some errors have detailed explanations: E0070, E0308, E0425.
---
126    |                    - ^
127    |                    |
128    |                    cannot assign to this expression
+    |
+ help: consider dereferencing here to assign a value to the left-hand side
+    |
+ LL -     let _: usize = 0 = 0;
+ LL +     let _: usize = 0 = 0;
129 
130 error[E0308]: mismatched types
131   --> $DIR/assignment-expected-bool.rs:31:20

---
To only update this specific test, also pass `--test-args type/type-check/assignment-expected-bool.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/type/type-check/assignment-expected-bool.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/type/type-check/assignment-expected-bool" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/type/type-check/assignment-expected-bool/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error[E0308]: mismatched types
  --> /checkout/src/test/ui/type/type-check/assignment-expected-bool.rs:6:19
   |
LL |     let _: bool = 0 = 0; //~ ERROR mismatched types [E0308]
   |                   ^^^^^ expected `bool`, found `()`
help: you might have meant to compare for equality
   |
   |
LL |     let _: bool = 0 == 0; //~ ERROR mismatched types [E0308]

error[E0308]: mismatched types
  --> /checkout/src/test/ui/type/type-check/assignment-expected-bool.rs:9:14
   |
   |
LL |         0 => 0 = 0, //~ ERROR mismatched types [E0308]
   |              ^^^^^ expected `bool`, found `()`
help: you might have meant to compare for equality
   |
   |
LL |         0 => 0 == 0, //~ ERROR mismatched types [E0308]

error[E0308]: mismatched types
  --> /checkout/src/test/ui/type/type-check/assignment-expected-bool.rs:10:14
   |
   |
LL |         _ => 0 = 0, //~ ERROR mismatched types [E0308]
   |              ^^^^^ expected `bool`, found `()`
help: you might have meant to compare for equality
   |
   |
LL |         _ => 0 == 0, //~ ERROR mismatched types [E0308]

error[E0308]: mismatched types
  --> /checkout/src/test/ui/type/type-check/assignment-expected-bool.rs:14:17
   |
   |
LL |         true => 0 = 0, //~ ERROR mismatched types [E0308]
   |                 ^^^^^ expected `bool`, found `()`
help: you might have meant to compare for equality
   |
   |
LL |         true => 0 == 0, //~ ERROR mismatched types [E0308]

error[E0308]: mismatched types
  --> /checkout/src/test/ui/type/type-check/assignment-expected-bool.rs:18:8
   |
   |
LL |     if 0 = 0 {} //~ ERROR mismatched types [E0308]
   |        ^^^^^ expected `bool`, found `()`
help: you might have meant to compare for equality
   |
   |
LL |     if 0 == 0 {} //~ ERROR mismatched types [E0308]

error[E0308]: mismatched types
  --> /checkout/src/test/ui/type/type-check/assignment-expected-bool.rs:20:24
   |
   |
LL |     let _: bool = if { 0 = 0 } { //~ ERROR mismatched types [E0308]
   |                        ^^^^^ expected `bool`, found `()`
help: you might have meant to compare for equality
   |
   |
LL |     let _: bool = if { 0 == 0 } { //~ ERROR mismatched types [E0308]

error[E0308]: mismatched types
  --> /checkout/src/test/ui/type/type-check/assignment-expected-bool.rs:21:9
   |
   |
LL |         0 = 0 //~ ERROR mismatched types [E0308]
   |         ^^^^^ expected `bool`, found `()`
help: you might have meant to compare for equality
   |
   |
LL |         0 == 0 //~ ERROR mismatched types [E0308]

error[E0308]: mismatched types
  --> /checkout/src/test/ui/type/type-check/assignment-expected-bool.rs:23:9
   |
   |
LL |         0 = 0 //~ ERROR mismatched types [E0308]
   |         ^^^^^ expected `bool`, found `()`
help: you might have meant to compare for equality
   |
   |
LL |         0 == 0 //~ ERROR mismatched types [E0308]

error[E0308]: mismatched types
  --> /checkout/src/test/ui/type/type-check/assignment-expected-bool.rs:26:13
   |
   |
LL |     let _ = (0 = 0) //~ ERROR mismatched types [E0308]
   |             ^^^^^^^ expected `bool`, found `()`
help: you might have meant to compare for equality
   |
   |
LL |     let _ = (0 == 0) //~ ERROR mismatched types [E0308]

error[E0308]: mismatched types
  --> /checkout/src/test/ui/type/type-check/assignment-expected-bool.rs:27:14
   |
   |
LL |         && { 0 = 0 } //~ ERROR mismatched types [E0308]
   |              ^^^^^ expected `bool`, found `()`
help: you might have meant to compare for equality
   |
   |
LL |         && { 0 == 0 } //~ ERROR mismatched types [E0308]

error[E0308]: mismatched types
  --> /checkout/src/test/ui/type/type-check/assignment-expected-bool.rs:28:12
   |
   |
LL |         || (0 = 0); //~ ERROR mismatched types [E0308]
   |            ^^^^^^^ expected `bool`, found `()`
help: you might have meant to compare for equality
   |
   |
LL |         || (0 == 0); //~ ERROR mismatched types [E0308]


error[E0070]: invalid left-hand side of assignment
   |
   |
LL |     let _: usize = 0 = 0;
   |                    - ^
   |                    cannot assign to this expression
   |
   |
help: consider dereferencing here to assign a value to the left-hand side
   |
LL -     let _: usize = 0 = 0;
LL +     let _: usize = 0 = 0;

error[E0308]: mismatched types
  --> /checkout/src/test/ui/type/type-check/assignment-expected-bool.rs:31:20
   |
   |
LL |     let _: usize = 0 = 0;
   |            -----   ^^^^^ expected `usize`, found `()`
   |            expected due to this

error: aborting due to 13 previous errors

compiler-errors · 2022-02-02T09:07:11Z

haha, forgot to consider the deref=0 case. let me fix that when i wake up tomorrow.

@rustbot author

compiler-errors · 2022-02-02T19:06:45Z

Actually this is already covered in check_ref, the error is just getting canceled for some reason. Let me investigate why.

compiler-errors added 2 commits February 2, 2022 00:00

suggest dereferencing lhs of assignment

37096e7

generalize deref suggestion even when lhs is assignable

5910263

rust-highfive assigned oli-obk Feb 2, 2022

rustbot added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Feb 2, 2022

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Feb 2, 2022

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Feb 2, 2022

compiler-errors closed this Feb 2, 2022

compiler-errors deleted the deref-on-assign-lhs branch April 7, 2022 04:34

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Suggest dereferencing LHS of assignment operator #93575

Suggest dereferencing LHS of assignment operator #93575

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compiler-errors commented Feb 2, 2022

Suggest dereferencing LHS of assignment operator #93575

Suggest dereferencing LHS of assignment operator #93575

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