Print types from applied functors in created interfaces by cknitt · Pull Request #9077 · rescript-lang/rescript

cknitt · 2026-10-27T13:14:00Z

Create interface copied each type declaration verbatim from the source file at the declaration's location. For a module created by applying a functor, or included from one, that location is inside the functor's body, possibly in another file. So the .resi got the unsubstituted body type or unrelated lines. Types declared outside the module being printed are now printed from the signature; local ones are still copied, keeping their attributes.

New analysis tests: CreateInterfaceFunctor (same file) and CreateInterfaceFunctorUse (functor from another file, module M = F(...) and include F(...)).

🤖 Generated with Claude Code

https://claude.ai/code/session_01Kbf3gLMawVgtmiKy3TMBc3

github-actions · 2026-10-27T13:14:25Z

Changelog

🐛 Bug fix

Editor "create interface" prints the types of applied functors and included modules instead of copying unrelated source lines.

Semantic Diff

3 commits · Full page

Print types from applied functors in created interfaces

_{a064592 · cknitt + Claude · Oct 27, 2026, 12:40 UTC}

Why

Create interface copied each type declaration from the source file at the declaration's location. A type of an applied functor or of an included module is located in the functor's body, possibly in another file, so the interface got the unsubstituted body type or whatever lines of the current file happened to be there. Types declared elsewhere are now printed from the signature.

Diagnostic modified (create interface)

module StrSet = CreateInterfaceFunctor.MakeSet({
  type t = string
  let compare = (a: string, b) => a < b ? -1 : a > b ? 1 : 0
})

rescript · tests/analysis_tests/tests/src/CreateInterfaceFunctorUse.res

 module StrSet: {
-
+  type t = array<string>
   let add: (t, string) => array<string>
 }

Review

Are types declared in the module itself still copied verbatim? Yes. A type is copied when its location is in the source file and, inside a nested module, within that module's declaration, so attributes on local declarations are kept as before.

Copy same-file types outside functors verbatim in created interfaces

_{de88a9c · cknitt + Claude · Oct 27, 2026, 17:33 UTC}

Codex review on #9077: a type of the same file reached through module type of or include was printed from the signature, which drops field attributes such as @as, so the interface no longer matched. Only types inside a functor body other than the module being printed, and types of other files, are printed from the signature now.

Print the runtime names of record fields from signatures

_{8a9ddb5 · cknitt + Claude · Oct 28, 2026, 07:39 UTC}

Review on #9077: a type of an applied functor is printed from its signature, and the printed record dropped @as on its fields, so the created interface for module M = F({}) with type t = {@as("wire") field: int} in F's body didn't match. Record fields in the outcome tree now carry their runtime name, and the printer writes it as @as, which also shows it in hover and error messages.

Diagnostic modified (created interface of an applied functor)

module WithWire = (X: {}) => {
  type t = {@as("wire") field: int}
}

module Applied = WithWire({})

rescript

 module Applied: {
-  type t = {field: int}
+  type t = {@as("wire") field: int}
 }

codecov · 2026-10-27T13:19:16Z

Codecov Report

❌ Patch coverage is 96.96970% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 81.46%. Comparing base (beb423d) to head (8a9ddb5).

Files with missing lines	Patch %	Lines
analysis/src/create_interface.ml	96.66%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #9077   +/-   ##
=======================================
  Coverage   81.45%   81.46%           
=======================================
  Files         460      460           
  Lines       64645    64664   +19     
=======================================
+ Hits        52657    52676   +19     
  Misses      11988    11988

Files with missing lines	Coverage Δ
analysis/src/cli.ml	`80.30% <ø> (ø)`
compiler/ml/printtyp.ml	`71.99% <ø> (ø)`
compiler/syntax/src/res_outcome_printer.ml	`82.27% <100.00%> (+0.11%)`	⬆️
analysis/src/create_interface.ml	`88.00% <96.66%> (+1.20%)`	⬆️

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pkg-pr-new · 2026-10-27T13:27:26Z

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rescript

npm i https://pkg.pr.new/rescript@9077

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npm i https://pkg.pr.new/@rescript/belt@9077

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npm i https://pkg.pr.new/@rescript/linux-x64@9077

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npm i https://pkg.pr.new/@rescript/runtime@9077

@rescript/win32-x64

npm i https://pkg.pr.new/@rescript/win32-x64@9077

commit: 8a9ddb5

github-actions · 2026-10-27T13:35:32Z

Developer playground preview: https://rescript-lang.github.io/rescript/dev-playground/?version=pr-9077

cknitt · 2026-10-27T14:20:00Z

@codex review

chatgpt-codex-connector · 2026-10-27T14:20:17Z

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-28T07:41:39.153785Z	`c6e8221`	Manual request

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Codex review on #9077: a type of the same file reached through `module type of` or `include` was printed from the signature, which drops field attributes such as `@as`, so the interface no longer matched. Only types inside a functor body other than the module being printed, and types of other files, are printed from the signature now. 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>

cknitt · 2026-10-27T17:33:54Z

@codex review

cristianoc

Approved, with one remaining interface-generation case worth addressing:

module F = (X: {}) => {
  type t = {@as("wire") field: int}
}
module M = F({})

For the applied module M, the synthetic printer drops @as("wire"), producing {field: int} and a signature mismatch. The path is analysis/src/create_interface.ml:288–290 → Printtyp.tree_of_label, which omits ld_runtime_name; Includecore.compare_records checks that runtime name. The latest fix preserves annotations for same-file types outside functors, but this applied-functor case remains.

This is based on source inspection; I have not run the repro locally.

@as

Review on #9077: a type of an applied functor is printed from its signature, and the printed record dropped `@as` on its fields, so the created interface for `module M = F({})` with `type t = {@as("wire") field: int}` in F's body didn't match. Record fields in the outcome tree now carry their runtime name, and the printer writes it as `@as`, which also shows it in hover and error messages. Diagnostic modified (created interface of an applied functor): Example: module WithWire = (X: {}) => { type t = {@as("wire") field: int} } module Applied = WithWire({}) Before (rescript): module Applied: { type t = {field: int} } After (rescript): module Applied: { type t = {@as("wire") field: int} } 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>

cknitt · 2026-10-28T07:39:59Z

Thanks, confirmed and fixed in c6e8221. Record fields in the outcome tree now carry their runtime name, and the outcome printer writes it as @as("…"), so module M = F({}) with type t = {@as("wire") field: int} in F's body gets type t = {@as("wire") field: int} in the created interface. CreateInterfaceFunctor.res has the case. The same printer is used by hover and error messages, which now show the runtime names too; the only other snapshot change is a JsxDOM.domProps hover listing its @as("aria-…") fields.

cknitt · 2026-10-28T07:40:01Z

@codex review

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Why: Create interface copied each type declaration from the source file at the declaration's location. A type of an applied functor or of an included module is located in the functor's body, possibly in another file, so the interface got the unsubstituted body type or whatever lines of the current file happened to be there. Types declared elsewhere are now printed from the signature. Diagnostic modified (create interface): Example: module StrSet = CreateInterfaceFunctor.MakeSet({ type t = string let compare = (a: string, b) => a < b ? -1 : a > b ? 1 : 0 }) Before (rescript): tests/analysis_tests/tests/src/CreateInterfaceFunctorUse.res module StrSet: { let add: (t, string) => array<string> } After (rescript): tests/analysis_tests/tests/src/CreateInterfaceFunctorUse.res module StrSet: { type t = array<string> let add: (t, string) => array<string> } Review: Are types declared in the module itself still copied verbatim? Yes. A type is copied when its location is in the source file and, inside a nested module, within that module's declaration, so attributes on local declarations are kept as before. Fixes: #9065 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>

Codex review on #9077: a type of the same file reached through `module type of` or `include` was printed from the signature, which drops field attributes such as `@as`, so the interface no longer matched. Only types inside a functor body other than the module being printed, and types of other files, are printed from the signature now. 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>

@as

Review on #9077: a type of an applied functor is printed from its signature, and the printed record dropped `@as` on its fields, so the created interface for `module M = F({})` with `type t = {@as("wire") field: int}` in F's body didn't match. Record fields in the outcome tree now carry their runtime name, and the printer writes it as `@as`, which also shows it in hover and error messages. Diagnostic modified (created interface of an applied functor): Example: module WithWire = (X: {}) => { type t = {@as("wire") field: int} } module Applied = WithWire({}) Before (rescript): module Applied: { type t = {field: int} } After (rescript): module Applied: { type t = {@as("wire") field: int} } 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>

cknitt marked this pull request as ready for review October 27, 2026 14:19

chatgpt-codex-connector Bot reviewed Oct 27, 2026

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Comment thread analysis/src/create_interface.ml

cknitt requested a review from cristianoc October 27, 2026 20:11

cristianoc approved these changes Oct 28, 2026

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chatgpt-codex-connector Bot reviewed Oct 28, 2026

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Comment thread analysis/src/create_interface.ml

cknitt and others added 3 commits October 28, 2026 07:48

cknitt mentioned this pull request Oct 28, 2026

Create interface drops attributes in front of type declarations #9095

Open

cknitt force-pushed the fix-9065-create-interface-functor-types branch from c6e8221 to 8a9ddb5 Compare October 28, 2026 08:10

cknitt mentioned this pull request Oct 28, 2026

Review of OCaml-derived language features #9074

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3 of 12 tasks

cknitt enabled auto-merge (squash) October 28, 2026 08:28

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