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Word signature mismatch errors in ReScript terms - #9078
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Semantic Diff2 commits · Full page ✏️ Indent multi-line types and signatures in error messagescbcd4f6 · Christoph Knittel + Claude · Oct 27, 2026, 19:53 UTC · edited The outcome printer rendered a type, signature or module type to a string and handed it to Format as one piece, so every line after the first started at column 0 instead of under its heading, and a short multi-line signature could share a line with the text around it. Each line break is now a newline of the enclosing Format box, and a multi-line piece makes that box break around it. Diagnostic modified (module mismatch) module type S = {
type t
}
module M: {
module F: (X: S) => S with type t = X.t
} = {
module F = (X: S) => {
type t = int
}
}
} is not included in
…
Modules do not match: {
type t = int} is not included in { type t = X.t}
Part of #9074. Review
Word signature mismatch errors in ReScript terms1db203e · cknitt + Claude · Oct 27, 2026, 12:41 UTC
Diagnostic modified (variant constructor mismatch) module M: {
type rec t<_> = Int(int): t<int> | Str(string): t<string>
} = {
type rec t<_> = Int(int): t<int> | Str(string): t<int>
}
-The types for field Str are not equal.
+The types for constructor Str are not equal.Diagnostic modified (functor position) module type S = {
type t
}
module M: {
module F: (X: S) => S with type t = X.t
} = {
module F = (X: S) => {
type t = int
}
}
-At position module F(X) : <here>
+At position module F: (X) => <here>Diagnostic modified (missing value)
-The value `b' is required but not provided
+The value `b` is required but not providedDiagnostic modified (extension constructor)
-type t += Boom(string)
+type t += Boom(string)Review
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Codecov Report❌ Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## fix-error-type-indentation #9078 +/- ##
==============================================================
+ Coverage 81.43% 81.45% +0.01%
==============================================================
Files 460 460
Lines 64634 64639 +5
==============================================================
+ Hits 52633 52649 +16
+ Misses 12001 11990 -11
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Codex Review: Didn't find any major issues. Nice work! Reviewed commit: ℹ️ About Codex in GitHubYour team has set up Codex to review pull requests in this repo. Reviews are triggered when you
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Why:
Inclusion errors still used OCaml wording: variant constructors were
called fields, functor positions were written as `module F(X) : ...`,
names were quoted as `x', and extension constructors were printed
with two spaces after `+=`.
Diagnostic modified (variant constructor mismatch):
Example:
module M: {
type rec t<_> = Int(int): t<int> | Str(string): t<string>
} = {
type rec t<_> = Int(int): t<int> | Str(string): t<int>
}
Before (diagnostic):
The types for field Str are not equal.
After (diagnostic):
The types for constructor Str are not equal.
Diagnostic modified (functor position):
Example:
module type S = {
type t
}
module M: {
module F: (X: S) => S with type t = X.t
} = {
module F = (X: S) => {
type t = int
}
}
Before (diagnostic):
At position module F(X) : <here>
After (diagnostic):
At position module F: (X) => <here>
Diagnostic modified (missing value):
Before (diagnostic):
The value `b' is required but not provided
After (diagnostic):
The value `b` is required but not provided
Diagnostic modified (extension constructor):
Before (diagnostic):
type t += Boom(string)
After (diagnostic):
type t += Boom(string)
Review: Do record fields keep their wording?
Yes. Only the comparison of variant constructors uses the new
constructor errors; inline record fields of a constructor are still
compared as fields.
Fixes: #9066
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Kbf3gLMawVgtmiKy3TMBc3
Signed-off-by: Christoph Knittel <ck@cca.io>
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Reviewed the wording-only delta on top of #9091, including constructor versus record-field errors, functor context rendering, and the new GADT/functor mismatch fixtures. No blocking issues found. CI checks inspected; tests were not rerun locally.
Fixes #9066. Stacked on #9091.
Signature mismatch errors now:
At position module F: (X) => <here>instead ofmodule F(X) : <here>);The value `b` is required);type t += Awith one space.New fixtures:
gadt_constructor_signature_mismatch,functor_signature_mismatch.🤖 Generated with Claude Code
https://claude.ai/code/session_01Kbf3gLMawVgtmiKy3TMBc3