Error messages: Improve "Somewhere wanted" messages (#6410)

* first batch of changes trying to improve the Somewhere wanted error messages

* tweaks

* add more fixtures

* remove redundant text

* add specialized errors for array items and setting record fields

* tweak set record field message

* hint about tuple in array message

* move message handling to own file

* cleanup

* cleanup

* cleanup

* cleanup

* changelog

* add example of tuple to error message

CHANGELOG.md

@@ -27,6 +27,7 @@
 
 - A little performance improvement for JSX V4 runtime helper by removing one object allocation for components with key prop. https://github.com/rescript-lang/rescript-compiler/pull/6376
 - The error message for "toplevel expressions should evaluate to unit" has been revamped and improved. https://github.com/rescript-lang/rescript-compiler/pull/6407
+- Improve "Somewhere wanted" error messages by changing wording and adding more context + suggested solutions to the error messages where appropriate. https://github.com/rescript-lang/rescript-compiler/pull/6410
 
 # 11.0.0-rc.3
 

jscomp/build_tests/super_errors/expected/array_item_type_mismatch.res.expected

@@ -0,0 +1,17 @@
+
+  We've found a bug for you!
+  /.../fixtures/array_item_type_mismatch.res:1:16-22
+
+  1 │ let x = [1, 2, "hello"]
+  2 │ 
+
+  This array item has type: string
+  But this array is expected to have items of type: int
+
+  Arrays can only contain items of the same type.
+
+  Possible solutions:
+  - Convert all values in the array to the same type.
+  - Use a tuple, if your array is of fixed length. Tuples can mix types freely, and compiles to a JavaScript array. Example of a tuple: `let myTuple = (10, "hello", 15.5, true)
+
+  You can convert string to int with Belt.Int.fromString.

jscomp/build_tests/super_errors/expected/collections.res.expected

@@ -7,6 +7,6 @@
   3 │ 
 
   This has type: string
-  Somewhere wanted: int
+  But it's expected to have type: int
 
   You can convert string to int with Belt.Int.fromString.

jscomp/build_tests/super_errors/expected/comparison_operator.res.expected

@@ -0,0 +1,13 @@
+
+  We've found a bug for you!
+  /.../fixtures/comparison_operator.res:3:17
+
+  1 │ let f = Some(0)
+  2 │ 
+  3 │ let x = 100 === f
+  4 │ 
+
+  This has type: option<int>
+  But it's being compared to something of type: int
+
+  You can only compare things of the same type.

jscomp/build_tests/super_errors/expected/function_argument_mismatch.res.expected

@@ -0,0 +1,13 @@
+
+  We've found a bug for you!
+  /.../fixtures/function_argument_mismatch.res:3:28-30
+
+  1 │ let makeName = (s, i) => s ++ i
+  2 │ 
+  3 │ let name = makeName("123", 123)
+  4 │ 
+
+  This has type: int
+  But this function argument is expecting: string
+
+  You can convert int to string with Belt.Int.toString.

jscomp/build_tests/super_errors/expected/function_call_mismatch.res.expected

@@ -0,0 +1,12 @@
+
+  We've found a bug for you!
+  /.../fixtures/function_call_mismatch.res:6:3-10
+
+  4 │ 
+  5 │ let cloneInTemp = (temp: string): string => {
+  6 │   cd(temp)
+  7 │   exec("git clone [email protected]:myorg/myrepo.git")
+  8 │ }
+
+  This function call returns: string
+  But it's expected to return: unit

jscomp/build_tests/super_errors/expected/function_return_mismatch.res.expected

@@ -0,0 +1,12 @@
+
+  We've found a bug for you!
+  /.../fixtures/function_return_mismatch.res:9:3-5
+
+   7 │ 
+   8 │ let x = fnExpectingCleanup(() => {
+   9 │   123
+  10 │ })
+  11 │ 
+
+  This has type: int
+  But it's expected to have type: cleanup (defined as unit => unit)

jscomp/build_tests/super_errors/expected/highlighting1.res.expected

@@ -8,6 +8,6 @@
   4 │ 
 
   This has type: string
-  Somewhere wanted: int
+  But it's expected to have type: int
 
   You can convert string to int with Belt.Int.fromString.

jscomp/build_tests/super_errors/expected/highlighting2.res.expected

@@ -9,6 +9,6 @@
   5 ┆ 
 
   This has type: string
-  Somewhere wanted: int
+  But it's expected to have type: int
 
   You can convert string to int with Belt.Int.fromString.

jscomp/build_tests/super_errors/expected/highlighting3.res.expected

@@ -9,6 +9,6 @@
   5 │ 
 
   This has type: string
-  Somewhere wanted: int
+  But it's expected to have type: int
 
   You can convert string to int with Belt.Int.fromString.

jscomp/build_tests/super_errors/expected/highlighting5.res.expected

@@ -8,6 +8,6 @@
   3 │ 
 
   This has type: string
-  Somewhere wanted: int
+  But it's expected to have type: int
 
   You can convert string to int with Belt.Int.fromString.

jscomp/build_tests/super_errors/expected/if_branch_mismatch.res.expected

@@ -0,0 +1,16 @@
+
+  We've found a bug for you!
+  /.../fixtures/if_branch_mismatch.res:4:3-5
+
+  2 │   "123"
+  3 │ } else {
+  4 │   123
+  5 │ }
+  6 │ 
+
+  This has type: int
+  But this if statement is expected to return: string
+
+  if expressions must return the same type in all branches (if, else if, else).
+
+  You can convert int to string with Belt.Int.toString.

jscomp/build_tests/super_errors/expected/if_condition_mismatch.res.expected

@@ -0,0 +1,12 @@
+
+  We've found a bug for you!
+  /.../fixtures/if_condition_mismatch.res:1:12-18
+
+  1 │ let x = if "horse" {
+  2 │   ()
+  3 │ }
+
+  This has type: string
+  But if conditions must always be of type: bool
+
+  To fix this, change the highlighted code so it evaluates to a bool.

jscomp/build_tests/super_errors/expected/math_operator_constant.res.expected

@@ -0,0 +1,20 @@
+
+  We've found a bug for you!
+  /.../fixtures/math_operator_constant.res:3:15-17
+
+  1 │ let num = 0
+  2 │ 
+  3 │ let x = num + 12.
+  4 │ 
+
+  This value has type: float
+  But it's being used with the + operator, which works on: int
+
+  Floats and ints have their own mathematical operators. This means you cannot add a float and an int without converting between the two.
+
+  Possible solutions:
+  - Ensure all values in this calculation has the type int. You can convert between floats and ints via Belt.Float.toInt and Belt.Int.fromFloat.
+  - Make 12. an int by removing the dot or explicitly converting to int
+
+  You can convert float to int with Belt.Float.toInt.
+  If this is a literal, try a number without a trailing dot (e.g. 20).

jscomp/build_tests/super_errors/expected/math_operator_float.res.expected

@@ -0,0 +1,20 @@
+
+  We've found a bug for you!
+  /.../fixtures/math_operator_float.res:3:9-11
+
+  1 │ let num = 0
+  2 │ 
+  3 │ let x = num +. 12.
+  4 │ 
+
+  This has type: int
+  But it's being used with the +. operator, which works on: float
+
+  Floats and ints have their own mathematical operators. This means you cannot add a float and an int without converting between the two.
+
+  Possible solutions:
+  - Ensure all values in this calculation has the type float. You can convert between floats and ints via Belt.Float.toInt and Belt.Int.fromFloat.
+  - Change the operator to +, which works on int
+
+  You can convert int to float with Belt.Int.toFloat.
+  If this is a literal, try a number with a trailing dot (e.g. 20.).

jscomp/build_tests/super_errors/expected/math_operator_int.res.expected

@@ -0,0 +1,20 @@
+
+  We've found a bug for you!
+  /.../fixtures/math_operator_int.res:3:9-11
+
+  1 │ let num = 0.
+  2 │ 
+  3 │ let x = num + 12.
+  4 │ 
+
+  This has type: float
+  But it's being used with the + operator, which works on: int
+
+  Floats and ints have their own mathematical operators. This means you cannot add a float and an int without converting between the two.
+
+  Possible solutions:
+  - Ensure all values in this calculation has the type int. You can convert between floats and ints via Belt.Float.toInt and Belt.Int.fromFloat.
+  - Change the operator to +., which works on float
+
+  You can convert float to int with Belt.Float.toInt.
+  If this is a literal, try a number without a trailing dot (e.g. 20).

jscomp/build_tests/super_errors/expected/primitives1.res.expected

@@ -6,8 +6,14 @@
   2 │ 2. + 2
   3 │ 
 
-  This has type: float
-  Somewhere wanted: int
+  This value has type: float
+  But it's being used with the + operator, which works on: int
+
+  Floats and ints have their own mathematical operators. This means you cannot add a float and an int without converting between the two.
+
+  Possible solutions:
+  - Ensure all values in this calculation has the type int. You can convert between floats and ints via Belt.Float.toInt and Belt.Int.fromFloat.
+  - Make 2. an int by removing the dot or explicitly converting to int
 
   You can convert float to int with Belt.Float.toInt.
   If this is a literal, try a number without a trailing dot (e.g. 20).

jscomp/build_tests/super_errors/expected/primitives11.res.expected

@@ -8,7 +8,7 @@
   6 │ 
 
   This has type: b (defined as option<bb>)
-  Somewhere wanted: a (defined as option<aa>)
+  But it's expected to have type: a (defined as option<aa>)
 
   The incompatible parts:
     bb (defined as option<int>) vs aa (defined as option<string>)

jscomp/build_tests/super_errors/expected/primitives2.res.expected

@@ -7,6 +7,6 @@
   3 │ 
 
   This has type: int
-  Somewhere wanted: string
+  But this function argument is expecting: string
 
   You can convert int to string with Belt.Int.toString.

jscomp/build_tests/super_errors/expected/primitives6.res.expected

@@ -8,7 +8,7 @@
   4 │ 
 
   This has type: int
-  Somewhere wanted: float
+  But it's expected to have type: float
 
   You can convert int to float with Belt.Int.toFloat.
   If this is a literal, try a number with a trailing dot (e.g. 20.).

jscomp/build_tests/super_errors/expected/primitives7.res.expected

@@ -8,7 +8,7 @@
   4 │ 
 
   This has type: list<int>
-  Somewhere wanted: list<float>
+  But this function argument is expecting: list<float>
 
   The incompatible parts:
     int vs float

jscomp/build_tests/super_errors/expected/primitives9.res.expected

@@ -6,6 +6,6 @@
   2 │ 
 
   This has type: string
-  Somewhere wanted: int
+  But it's expected to have type: int
 
   You can convert string to int with Belt.Int.fromString.

jscomp/build_tests/super_errors/expected/record_type_spreads_deep_sub.res.expected

@@ -9,6 +9,6 @@
   10 │ 
 
   This has type: string
-  Somewhere wanted: int
+  But it's expected to have type: int
 
   You can convert string to int with Belt.Int.fromString.

jscomp/build_tests/super_errors/expected/set_record_field_type_match.res.expected

@@ -0,0 +1,13 @@
+
+  We've found a bug for you!
+  /.../fixtures/set_record_field_type_match.res:11:13-14
+
+   9 │ }
+  10 │ 
+  11 │ user.name = 12
+  12 │ 
+
+  You're assigning something to this field that has type: int
+  But this record field is of type: string
+
+  You can convert int to string with Belt.Int.toString.

jscomp/build_tests/super_errors/expected/switch_different_types.res.expected

@@ -0,0 +1,14 @@
+
+  We've found a bug for you!
+  /.../fixtures/switch_different_types.res:7:10-23
+
+  5 │   switch foo {
+  6 │   | "world" => ()
+  7 │   | _ => someFunction()
+  8 │   }
+  9 │ }
+
+  This has type: string
+  But this switch is expected to return: unit
+
+  All branches in a switch must return the same type. To fix this, change your branch to return the expected type.

jscomp/build_tests/super_errors/expected/switch_guard.res.expected

@@ -0,0 +1,14 @@
+
+  We've found a bug for you!
+  /.../fixtures/switch_guard.res:6:16-22
+
+  4 │ let bar = () => {
+  5 │   switch foo {
+  6 │   | "world" if "horse" => ()
+  7 │   | _ => someFunction()
+  8 │   }
+
+  This has type: string
+  But if conditions must always be of type: bool
+
+  To fix this, change the highlighted code so it evaluates to a bool.

jscomp/build_tests/super_errors/expected/syntaxErrors4.res.expected

@@ -13,6 +13,6 @@
   23 │ /* */
 
   This has type: string
-  Somewhere wanted: int
+  But it's expected to have type: int
 
   You can convert string to int with Belt.Int.fromString.

jscomp/build_tests/super_errors/expected/type1.res.expected

@@ -5,8 +5,14 @@
   1 │ let x = 2. + 2
   2 │ 
 
-  This has type: float
-  Somewhere wanted: int
+  This value has type: float
+  But it's being used with the + operator, which works on: int
+
+  Floats and ints have their own mathematical operators. This means you cannot add a float and an int without converting between the two.
+
+  Possible solutions:
+  - Ensure all values in this calculation has the type int. You can convert between floats and ints via Belt.Float.toInt and Belt.Int.fromFloat.
+  - Make 2. an int by removing the dot or explicitly converting to int
 
   You can convert float to int with Belt.Float.toInt.
   If this is a literal, try a number without a trailing dot (e.g. 20).

jscomp/build_tests/super_errors/expected/type2.res.expected

@@ -9,6 +9,6 @@
   8 │ 
 
   This has type: string
-  Somewhere wanted: int
+  But this function argument is expecting: int
 
   You can convert string to int with Belt.Int.fromString.

jscomp/build_tests/super_errors/expected/unicode_location.res.expected

@@ -7,6 +7,6 @@
     │ (unicode symbols of length 2)
 
   This has type: int
-  Somewhere wanted: string
+  But this function argument is expecting: string
 
   You can convert int to string with Belt.Int.toString.