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[Patterns] remove irrelevant specification of pattern type schemas. #2639

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merged 2 commits into from
Nov 17, 2022
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[Patterns] remove irrelevant specification of pattern type schemas. #2639

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[Patterns] remove irrelevant specification of pattern type schemas.
stereotype441 Nov 16, 2022
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Address review comment
stereotype441 Nov 17, 2022
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16 changes: 7 additions & 9 deletions accepted/future-releases/0546-patterns/feature-specification.md
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Expand Up @@ -1570,22 +1570,16 @@ var (a, int b) = ... // Schema is `(?, int)`.

The context type schema for a pattern `p` is:

* **Logical-or**: The least upper bound of the context type schemas of the
branches.

* **Logical-and**: The greatest lower bound of the context type schemas of the
branches.

* **Null-check** or **null-assert**: A context type schema `E?` where `E` is
the context type schema of the inner pattern. *For example:*
* **Null-assert**: A context type schema `E?` where `E` is the context type
schema of the inner pattern. *For example:*

```dart
var [[int x]!] = [[]]; // Infers List<List<int>?> for the list literal.
```

* **Constant**: The context type schema is the static type of the pattern's
value.

* **Variable**:

1. In an assignment context, the context type schema is the static type of
Expand All @@ -1604,7 +1598,7 @@ The context type schema for a pattern `p` is:
// ^- Infers List<int>.
```

* **Relational** or **cast**: The context type schema is `?`.
* **Cast**: The context type schema is `?`.

* **Parenthesized**: The context type schema of the inner subpattern.

Expand Down Expand Up @@ -1675,6 +1669,10 @@ The context type schema for a pattern `p` is:
// ^-- Infer Foo<num>.
```

The pattern type schema for logical-or, null-check, constant, and relational
patterns is not defined, because those patterns are only allowed in refutable
contexts, and the pattern type schema is only used in irrefutable contexts.

#### Type checking and pattern required type

Once the value a pattern is matched against has a static type (which means
Expand Down