[flow] Scope analysis for declare global {...}

Summary:
This diff adds scope analysis for local checking of `declare global {...}`.

Note that we don't have to do it for normal modules, since by the time we are checking normal modules, it will already have the extended globals injected into the context from type sig, so it doesn't have to read the globals from nested `declare global` block.

For `declare global` within `declare module`, we special case it during scope analysis. We first hoist all the globals within declare global within the declare module, create a scope with it, and then create a scope for everything else. This will implement the scoping rule as described in D68246824.

With this setup, we have the feature mostly working, and the only two issue remainings are globalThis interaction, and missing error for having value-decls within the declare global block.

Changelog: [internal]

Reviewed By: panagosg7

Differential Revision: D68851619

fbshipit-source-id: 1122ee2ec84fb0b6df6e7a3f47529ce3c2be6e50

src/analysis/env_builder/name_resolver.ml

@@ -6311,18 +6311,54 @@ module Make (Context : C) (FlowAPIUtils : F with type cx = Context.t) :
         let v = val_simplify def_loc (Val.SourceLevelBinding kind) (Some name) v in
         v
 
-      method! declare_module _loc ({ Ast.Statement.DeclareModule.id = _; body; _ } as m) =
+      method! declare_module loc ({ Ast.Statement.DeclareModule.id = _; body; _ } as m) =
         let (block_loc, { Ast.Statement.Block.body = statements; comments = _ }) = body in
-        let bindings =
-          let hoist =
-            new Hoister.hoister ~flowmin_compatibility:false ~enable_enums ~with_types:true
+        let within_possible_declare_globals ~f =
+          let declare_global_bodies =
+            Base.List.filter_map statements ~f:(function
+                | ( _,
+                    Ast.Statement.DeclareNamespace
+                      {
+                        Ast.Statement.DeclareNamespace.id = Ast.Statement.DeclareNamespace.Global _;
+                        body;
+                        comments = _;
+                      }
+                  ) ->
+                  Some body
+                | _ -> None
+                )
           in
-          hoist#eval hoist#statement_list statements
+          if Base.List.is_empty declare_global_bodies then
+            f ()
+          else
+            let hoist = new hoister ~flowmin_compatibility:false ~enable_enums ~with_types:true in
+            Base.List.iter declare_global_bodies ~f:(fun (loc, body) ->
+                Flow_ast_visitor.run (hoist#block loc) body
+            );
+            let global_bindings = hoist#acc in
+            this#with_bindings
+              loc
+              global_bindings
+              (fun () ->
+                Base.List.iter declare_global_bodies ~f:(fun (loc, body) ->
+                    Flow_ast_visitor.run (this#block loc) body
+                );
+                f ())
+              ();
+            ()
         in
-        let saved_exclude_syms = env_state.exclude_syms in
-        env_state <- { env_state with exclude_syms = SSet.empty };
-        ignore @@ this#statements_with_bindings block_loc bindings statements;
-        env_state <- { env_state with exclude_syms = saved_exclude_syms };
+        within_possible_declare_globals ~f:(fun () ->
+            let bindings =
+              let hoist =
+                new Hoister.hoister ~flowmin_compatibility:false ~enable_enums ~with_types:true
+              in
+              hoist#eval hoist#statement_list statements
+            in
+            let saved_exclude_syms = env_state.exclude_syms in
+            env_state <- { env_state with exclude_syms = SSet.empty };
+            ignore @@ this#statements_with_bindings block_loc bindings statements;
+            env_state <- { env_state with exclude_syms = saved_exclude_syms }
+        );
         m
 
       method! declare_namespace loc ({ Ast.Statement.DeclareNamespace.id; body; _ } as m) =

src/analysis/scope_builder.ml

@@ -601,12 +601,46 @@ module Make (L : Loc_sig.S) (Api : Scope_api_sig.S with module L = L) :
         let open Ast.Statement.DeclareModule in
         let { id = _; body; comments = _ } = m in
         let (loc, body) = body in
-        let bindings =
-          let hoist = new hoister ~flowmin_compatibility ~enable_enums ~with_types in
-          run (hoist#block loc) body;
-          hoist#acc
+        let within_possible_declare_globals ~f =
+          let declare_global_bodies =
+            Base.List.filter_map body.Ast.Statement.Block.body ~f:(function
+                | ( _,
+                    Ast.Statement.DeclareNamespace
+                      {
+                        Ast.Statement.DeclareNamespace.id = Ast.Statement.DeclareNamespace.Global _;
+                        body;
+                        comments = _;
+                      }
+                  ) ->
+                  Some body
+                | _ -> None
+                )
+          in
+          if Base.List.is_empty declare_global_bodies then
+            f ()
+          else
+            let hoist = new hoister ~flowmin_compatibility ~enable_enums ~with_types in
+            Base.List.iter declare_global_bodies ~f:(fun (loc, body) -> run (hoist#block loc) body);
+            let global_bindings = hoist#acc in
+            this#with_bindings
+              loc
+              global_bindings
+              (fun () ->
+                Base.List.iter declare_global_bodies ~f:(fun (loc, body) ->
+                    run (this#block loc) body
+                );
+                f ())
+              ();
+            ()
         in
-        this#with_bindings loc bindings (fun () -> run (this#block loc) body) ();
+        within_possible_declare_globals ~f:(fun () ->
+            let bindings =
+              let hoist = new hoister ~flowmin_compatibility ~enable_enums ~with_types in
+              run (hoist#block loc) body;
+              hoist#acc
+            in
+            this#with_bindings loc bindings (fun () -> run (this#block loc) body) ()
+        );
         m
 
       method! declare_namespace _loc n =

src/typing/statement.ml

@@ -2106,10 +2106,16 @@ module Make
               reason
               body_statements
           in
-          Flow.add_output
-            cx
-            (Error_message.EUnsupportedSyntax (name_loc, Flow_intermediate_error_types.DeclareGlobal)
-            );
+          let () =
+            match (Context.enable_declare_global cx, prev_scope_kind) with
+            | (true, (Name_def.DeclareModule | Name_def.Module)) -> ()
+            | (_, _) ->
+              Flow.add_output
+                cx
+                (Error_message.EUnsupportedSyntax
+                   (name_loc, Flow_intermediate_error_types.DeclareGlobal)
+                )
+          in
           Flow.add_output cx (Error_message.EUndocumentedFeature { loc = name_loc });
           (t, Ast.Statement.DeclareNamespace.Global id)
         | Ast.Statement.DeclareNamespace.Local id ->

src/typing/type_inference_js.ml

@@ -469,9 +469,9 @@ class lib_def_loc_mapper_and_validator cx =
         | DeclareNamespace.Local _ -> None
         | DeclareNamespace.Global _ ->
           if in_toplevel_scope then
-            None
+            Some (error "declare global")
           else
-            Some (error "declare global"))
+            None)
       | Block _ -> Some (error "block")
       | Break _ -> Some (error "break")
       | ClassDeclaration _ -> Some (error "class declaration")

tests/declare_global_in_react_declare_module/.flowconfig

@@ -0,0 +1,7 @@
+[libs]
+react.js
+
+[options]
+all=true
+experimental.declare_global=true
+no_flowlib=false

tests/declare_global_in_react_declare_module/declare_global_in_react_declare_module.exp

@@ -0,0 +1,89 @@
+Error --------------------------------------------------------------------------------------------------- react.js:10:10
+
+Cannot redeclare global `React.Node` [1] because the global is already declared in another file. [name-already-bound]
+
+   react.js:10:10
+   10|     type React$Node = 1; // bad-shadow
+                ^^^^^^^^^^
+
+References:
+   <BUILTINS>/react.js:15:14
+   15| declare type React$Node =
+                    ^^^^^^^^^^ [1]
+
+
+Error ------------------------------------------------------------------------------------------------------ test.js:2:1
+
+Cannot cast `2` to `React.Node` because number [1] is incompatible with number literal `1` [2]. [incompatible-cast]
+
+   test.js:2:1
+   2| 2 as React$Node; // error: 2 ~> 1: The bad shadow wins over the real global.
+      ^ [1]
+
+References:
+   test.js:2:6
+   2| 2 as React$Node; // error: 2 ~> 1: The bad shadow wins over the real global.
+           ^^^^^^^^^^ [2]
+
+
+Error ------------------------------------------------------------------------------------------------------ test.js:3:1
+
+Cannot cast empty string to `MyReact` because string [1] is incompatible with string literal `react` [2].
+[incompatible-cast]
+
+   test.js:3:1
+   3| '' as ReactTypes.MyReact; // error: '' ~> 'react'
+      ^^ [1]
+
+References:
+   test.js:3:7
+   3| '' as ReactTypes.MyReact; // error: '' ~> 'react'
+            ^^^^^^^^^^^^^^^^^^ [2]
+
+
+Error ------------------------------------------------------------------------------------------------------ test.js:4:1
+
+Cannot resolve name `ReactValue`. [cannot-resolve-name]
+
+   4| ReactValue; // error: value-namespaces in declare global are completely ignored
+      ^^^^^^^^^^
+
+
+Error ------------------------------------------------------------------------------------------------------ test.js:5:1
+
+Cannot resolve name `willBeIgnored`. [cannot-resolve-name]
+
+   5| willBeIgnored; // error: values in declare global are completely ignored
+      ^^^^^^^^^^^^^
+
+
+Error ------------------------------------------------------------------------------------------------------ test.js:8:1
+
+Cannot cast empty string to `T1` because string [1] is incompatible with string literal `react` [2]. [incompatible-cast]
+
+   test.js:8:1
+   8| '' as T1; // error: '' ~> 'react'
+      ^^ [1]
+
+References:
+   test.js:8:7
+   8| '' as T1; // error: '' ~> 'react'
+            ^^ [2]
+
+
+Error ------------------------------------------------------------------------------------------------------ test.js:9:1
+
+Cannot cast empty string to `T2` because string [1] is incompatible with number literal `3` [2]. [incompatible-cast]
+
+   test.js:9:1
+   9| '' as T2 // error: '' ~> 3
+      ^^ [1]
+
+References:
+   test.js:9:7
+   9| '' as T2 // error: '' ~> 3
+            ^^ [2]
+
+
+
+Found 7 errors

tests/declare_global_in_react_declare_module/react.js

@@ -0,0 +1,17 @@
+declare module 'react' {
+  // $FlowExpectedError[undocumented-feature]
+  declare global {
+    declare namespace ReactTypes {
+      type MyReact = 'react';
+    }
+    declare namespace ReactValue { // TODO error: error on ignored value defs in declare global
+      declare const willBeIgnored: string;
+    }
+    type React$Node = 1; // bad-shadow
+    type ReactGlobalType = 3;
+    declare const willBeIgnored: string;
+  }
+
+  export type T1 = ReactTypes.MyReact;
+  export type T2 = ReactGlobalType;
+}

tests/declare_global_in_react_declare_module/test.js

@@ -0,0 +1,9 @@
+// $FlowExpectedError[internal-type]
+2 as React$Node; // error: 2 ~> 1: The bad shadow wins over the real global.
+'' as ReactTypes.MyReact; // error: '' ~> 'react'
+ReactValue; // error: value-namespaces in declare global are completely ignored
+willBeIgnored; // error: values in declare global are completely ignored
+
+import type {T1, T2} from 'react'; // test that the normal exported types can reference names within declare global
+'' as T1; // error: '' ~> 'react'
+'' as T2 // error: '' ~> 3

tests/declare_global_in_react_module/.flowconfig

@@ -0,0 +1,4 @@
+[options]
+all=true
+experimental.declare_global=true
+no_flowlib=false

tests/declare_global_in_react_module/@flowtyped/react.js.flow

@@ -0,0 +1,15 @@
+// $FlowExpectedError[undocumented-feature]
+declare global {
+  declare namespace ReactTypes {
+    type MyReact = 'react';
+  }
+  declare namespace ReactValue { // TODO error: error on ignored value defs in declare global
+    declare const willBeIgnored: string;
+  }
+  type React$Node = 1; // bad-shadow
+  type ReactGlobalType = 3;
+  declare const willBeIgnored: string;
+}
+
+export type T1 = ReactTypes.MyReact;
+export type T2 = ReactGlobalType;

tests/declare_global_in_react_module/declare_global_in_react_module.exp

@@ -0,0 +1,89 @@
+Error ------------------------------------------------------------------------------------- @flowtyped/react.js.flow:9:8
+
+Cannot redeclare global `React.Node` [1] because the global is already declared in another file. [name-already-bound]
+
+   @flowtyped/react.js.flow:9:8
+    9|   type React$Node = 1; // bad-shadow
+              ^^^^^^^^^^
+
+References:
+   <BUILTINS>/react.js:15:14
+   15| declare type React$Node =
+                    ^^^^^^^^^^ [1]
+
+
+Error ------------------------------------------------------------------------------------------------------ test.js:2:1
+
+Cannot cast `2` to `React.Node` because number [1] is incompatible with number literal `1` [2]. [incompatible-cast]
+
+   test.js:2:1
+   2| 2 as React$Node; // error: 2 ~> 1: The bad shadow wins over the real global.
+      ^ [1]
+
+References:
+   test.js:2:6
+   2| 2 as React$Node; // error: 2 ~> 1: The bad shadow wins over the real global.
+           ^^^^^^^^^^ [2]
+
+
+Error ------------------------------------------------------------------------------------------------------ test.js:3:1
+
+Cannot cast empty string to `MyReact` because string [1] is incompatible with string literal `react` [2].
+[incompatible-cast]
+
+   test.js:3:1
+   3| '' as ReactTypes.MyReact; // error: '' ~> 'react'
+      ^^ [1]
+
+References:
+   test.js:3:7
+   3| '' as ReactTypes.MyReact; // error: '' ~> 'react'
+            ^^^^^^^^^^^^^^^^^^ [2]
+
+
+Error ------------------------------------------------------------------------------------------------------ test.js:4:1
+
+Cannot resolve name `ReactValue`. [cannot-resolve-name]
+
+   4| ReactValue; // error: value-namespaces in declare global are completely ignored
+      ^^^^^^^^^^
+
+
+Error ------------------------------------------------------------------------------------------------------ test.js:5:1
+
+Cannot resolve name `willBeIgnored`. [cannot-resolve-name]
+
+   5| willBeIgnored; // error: values in declare global are completely ignored
+      ^^^^^^^^^^^^^
+
+
+Error ------------------------------------------------------------------------------------------------------ test.js:8:1
+
+Cannot cast empty string to `T1` because string [1] is incompatible with string literal `react` [2]. [incompatible-cast]
+
+   test.js:8:1
+   8| '' as T1; // error: '' ~> 'react'
+      ^^ [1]
+
+References:
+   test.js:8:7
+   8| '' as T1; // error: '' ~> 'react'
+            ^^ [2]
+
+
+Error ------------------------------------------------------------------------------------------------------ test.js:9:1
+
+Cannot cast empty string to `T2` because string [1] is incompatible with number literal `3` [2]. [incompatible-cast]
+
+   test.js:9:1
+   9| '' as T2 // error: '' ~> 3
+      ^^ [1]
+
+References:
+   test.js:9:7
+   9| '' as T2 // error: '' ~> 3
+            ^^ [2]
+
+
+
+Found 7 errors

tests/declare_global_in_react_module/test.js

@@ -0,0 +1,9 @@
+// $FlowExpectedError[internal-type]
+2 as React$Node; // error: 2 ~> 1: The bad shadow wins over the real global.
+'' as ReactTypes.MyReact; // error: '' ~> 'react'
+ReactValue; // error: value-namespaces in declare global are completely ignored
+willBeIgnored; // error: values in declare global are completely ignored
+
+import type {T1, T2} from 'react'; // test that the normal exported types can reference names within declare global
+'' as T1; // error: '' ~> 'react'
+'' as T2 // error: '' ~> 3