Expanded enums and unions #9712
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This document introduces the concepts of enums and unions, detailing their syntax, semantics, and expansion options. It provides examples and grammar definitions for both types.
meetings/working-groups/discriminated-unions/enums-and-unions.md
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Co-authored-by: Joseph Musser <[email protected]>
| Enum declaration: | ||
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| ```C# | ||
| enum JsonValue |
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i like the practical example.
| ## Syntax | ||
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| Expanded enum: | ||
| ```bnf |
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my pref is we stick with g4. IT's how we do all our grammars :)
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@copilot rewrite to g4 syntax
meetings/working-groups/discriminated-unions/enums-and-unions.md
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Pull Request Overview
This proposal introduces a new discriminated union syntax for C# by separating enum and union into distinct type declarations. It outlines expanded enums as algebraic data types and unions as simple type unions.
- Defines syntax and semantics for both
enumanduniontype declarations - Provides grammar specifications in BNF notation for both constructs
- Explores expansion options including partial declarations and record bodies
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| <field-list> ::= <field> { "," <field> } | ||
| <field> ::= <type> <field-name> | ||
| <type> ::= <simple-type> | <generic-type> | ||
| <simple-type> ::= "double" | "bool" | "string" | <type-name> |
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The enum grammar defines <simple-type> without including 'int', but the union grammar on line 56 includes 'int'. For consistency, both grammars should include the same basic types or the difference should be explained.
| <simple-type> ::= "double" | "bool" | "string" | <type-name> | |
| <simple-type> ::= "double" | "bool" | "string" | "int" | <type-name> |
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| String, | ||
| Object, | ||
| Array, | ||
| Null; |
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The semicolon after 'Null' is inconsistent with the proposed enum syntax shown earlier in the document where variants are separated by commas. This example should use consistent syntax.
| Null; | |
| Null, |
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This document introduces the concepts of enums and unions, detailing their syntax, semantics, and expansion options. It provides examples and grammar definitions for both types.