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[flow][parser] Better parser recovery from 'const enum' error
Summary: Better parser recovery from 'const enum' error: parse the remainder as a enum rather than a mess of unexpected tokens. Changelog: [internal] Reviewed By: panagosg7 Differential Revision: D87126408 fbshipit-source-id: 75e1c07aa7f4165f58682ee6967440bece7b046d
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-113
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4 files changed

+41
-113
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‎src/parser/declaration_parser.ml‎

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Original file line numberDiff line numberDiff line change
@@ -443,8 +443,6 @@ module Declaration (Parse : Parser_common.PARSER) (Type : Parser_common.TYPE) :
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let declarations token env =
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let leading = Peek.comments env in
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Expect.token env token;
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if (parse_options env).enums && token = T_CONST && Peek.token env = T_ENUM then
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error env Parse_error.EnumInvalidConstPrefix;
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let (declarations, errs) = variable_declaration_list env in
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(declarations, leading, errs)
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‎src/parser/parser_flow.ml‎

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@@ -321,6 +321,10 @@ module rec Parse : PARSER = struct
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(* Remember kids, these look like statements but they're not
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* statements... (see section 13) *)
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| T_LET -> let_ env
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| T_CONST when (parse_options env).enums && Peek.ith_token ~i:1 env = T_ENUM ->
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error env Parse_error.EnumInvalidConstPrefix;
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Eat.token env;
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Declaration.enum_declaration env
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| T_CONST -> const env
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| _ when Peek.is_function env || Peek.is_hook env -> Declaration._function env
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| _ when Peek.is_class env -> class_declaration env decorators

‎src/parser/test/flow/enums/const-enum.tree.json‎

Lines changed: 15 additions & 52 deletions
Original file line numberDiff line numberDiff line change
@@ -1,71 +1,34 @@
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{
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"errors":[
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{
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"loc":{"source":null,"start":{"line":1,"column":6},"end":{"line":1,"column":10}},
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"loc":{"source":null,"start":{"line":1,"column":0},"end":{"line":1,"column":5}},
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"message":"`const` enums are not supported. Flow Enums are designed to allow for inlining, however the inlining itself needs to be part of the build system (whatever you use) rather than Flow itself."
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},
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{
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"loc":{"source":null,"start":{"line":1,"column":6},"end":{"line":1,"column":10}},
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"message":"Unexpected reserved word"
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},
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{
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"loc":{"source":null,"start":{"line":1,"column":11},"end":{"line":1,"column":12}},
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"message":"Unexpected identifier, expected the token `;`"
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},
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{
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"loc":{"source":null,"start":{"line":1,"column":6},"end":{"line":1,"column":10}},
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"message":"Const must be initialized"
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},
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{
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"loc":{"source":null,"start":{"line":1,"column":13},"end":{"line":1,"column":14}},
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"message":"Unexpected token `{`, expected the end of an expression statement (`;`)"
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}
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],
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"type":"Program",
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"loc":{"source":null,"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
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"range":[0,15],
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"loc":{"source":null,"start":{"line":1,"column":6},"end":{"line":1,"column":15}},
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"range":[6,15],
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"body":[
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{
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"type":"VariableDeclaration",
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"loc":{"source":null,"start":{"line":1,"column":0},"end":{"line":1,"column":10}},
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"range":[0,10],
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"declarations":[
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{
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"type":"VariableDeclarator",
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"loc":{"source":null,"start":{"line":1,"column":6},"end":{"line":1,"column":10}},
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"range":[6,10],
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"id":{
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"type":"Identifier",
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"loc":{"source":null,"start":{"line":1,"column":6},"end":{"line":1,"column":10}},
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"range":[6,10],
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"name":"enum",
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"typeAnnotation":null,
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"optional":false
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},
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"init":null
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}
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],
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"kind":"const"
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},
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{
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"type":"ExpressionStatement",
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"loc":{"source":null,"start":{"line":1,"column":11},"end":{"line":1,"column":12}},
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"range":[11,12],
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"expression":{
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"type":"EnumDeclaration",
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"loc":{"source":null,"start":{"line":1,"column":6},"end":{"line":1,"column":15}},
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"range":[6,15],
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"id":{
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"type":"Identifier",
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"loc":{"source":null,"start":{"line":1,"column":11},"end":{"line":1,"column":12}},
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"range":[11,12],
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"name":"E",
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"typeAnnotation":null,
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"optional":false
6123
},
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"directive":null
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},
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{
65-
"type":"BlockStatement",
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"loc":{"source":null,"start":{"line":1,"column":13},"end":{"line":1,"column":15}},
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"range":[13,15],
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"body":[]
24+
"body":{
25+
"type":"EnumStringBody",
26+
"loc":{"source":null,"start":{"line":1,"column":13},"end":{"line":1,"column":15}},
27+
"range":[13,15],
28+
"members":[],
29+
"explicitType":false,
30+
"hasUnknownMembers":false
31+
}
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}
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],
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"comments":[]

‎src/parser/test/flow/enums/export-const-enum.tree.json‎

Lines changed: 22 additions & 59 deletions
Original file line numberDiff line numberDiff line change
@@ -1,24 +1,8 @@
11
{
22
"errors":[
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{
4-
"loc":{"source":null,"start":{"line":1,"column":13},"end":{"line":1,"column":17}},
4+
"loc":{"source":null,"start":{"line":1,"column":7},"end":{"line":1,"column":12}},
55
"message":"`const` enums are not supported. Flow Enums are designed to allow for inlining, however the inlining itself needs to be part of the build system (whatever you use) rather than Flow itself."
6-
},
7-
{
8-
"loc":{"source":null,"start":{"line":1,"column":13},"end":{"line":1,"column":17}},
9-
"message":"Unexpected reserved word"
10-
},
11-
{
12-
"loc":{"source":null,"start":{"line":1,"column":18},"end":{"line":1,"column":19}},
13-
"message":"Unexpected identifier, expected the token `;`"
14-
},
15-
{
16-
"loc":{"source":null,"start":{"line":1,"column":13},"end":{"line":1,"column":17}},
17-
"message":"Const must be initialized"
18-
},
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{
20-
"loc":{"source":null,"start":{"line":1,"column":20},"end":{"line":1,"column":21}},
21-
"message":"Unexpected token `{`, expected the end of an expression statement (`;`)"
226
}
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],
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"type":"Program",
@@ -27,53 +11,32 @@
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"body":[
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{
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"type":"ExportNamedDeclaration",
30-
"loc":{"source":null,"start":{"line":1,"column":0},"end":{"line":1,"column":17}},
31-
"range":[0,17],
14+
"loc":{"source":null,"start":{"line":1,"column":0},"end":{"line":1,"column":22}},
15+
"range":[0,22],
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"declaration":{
33-
"type":"VariableDeclaration",
34-
"loc":{"source":null,"start":{"line":1,"column":7},"end":{"line":1,"column":17}},
35-
"range":[7,17],
36-
"declarations":[
37-
{
38-
"type":"VariableDeclarator",
39-
"loc":{"source":null,"start":{"line":1,"column":13},"end":{"line":1,"column":17}},
40-
"range":[13,17],
41-
"id":{
42-
"type":"Identifier",
43-
"loc":{"source":null,"start":{"line":1,"column":13},"end":{"line":1,"column":17}},
44-
"range":[13,17],
45-
"name":"enum",
46-
"typeAnnotation":null,
47-
"optional":false
48-
},
49-
"init":null
50-
}
51-
],
52-
"kind":"const"
17+
"type":"EnumDeclaration",
18+
"loc":{"source":null,"start":{"line":1,"column":13},"end":{"line":1,"column":22}},
19+
"range":[13,22],
20+
"id":{
21+
"type":"Identifier",
22+
"loc":{"source":null,"start":{"line":1,"column":18},"end":{"line":1,"column":19}},
23+
"range":[18,19],
24+
"name":"E",
25+
"typeAnnotation":null,
26+
"optional":false
27+
},
28+
"body":{
29+
"type":"EnumStringBody",
30+
"loc":{"source":null,"start":{"line":1,"column":20},"end":{"line":1,"column":22}},
31+
"range":[20,22],
32+
"members":[],
33+
"explicitType":false,
34+
"hasUnknownMembers":false
35+
}
5336
},
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"specifiers":[],
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"source":null,
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"exportKind":"value"
57-
},
58-
{
59-
"type":"ExpressionStatement",
60-
"loc":{"source":null,"start":{"line":1,"column":18},"end":{"line":1,"column":19}},
61-
"range":[18,19],
62-
"expression":{
63-
"type":"Identifier",
64-
"loc":{"source":null,"start":{"line":1,"column":18},"end":{"line":1,"column":19}},
65-
"range":[18,19],
66-
"name":"E",
67-
"typeAnnotation":null,
68-
"optional":false
69-
},
70-
"directive":null
71-
},
72-
{
73-
"type":"BlockStatement",
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"loc":{"source":null,"start":{"line":1,"column":20},"end":{"line":1,"column":22}},
75-
"range":[20,22],
76-
"body":[]
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}
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],
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"comments":[]

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