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Clarify section on MIR construction

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Camelid 2020-08-22 18:51:53 -07:00 committed by Tshepang Lekhonkhobe
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commit 014d434f46
1 changed files with 6 additions and 5 deletions
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@ -3,10 +3,10 @@
The lowering of [HIR] to [MIR] occurs for the following (probably incomplete)
list of items:
* Function and Closure bodies
* Function and closure bodies
* Initializers of `static` and `const` items
* Initializers of enum discriminants
* Glue and Shims of any kind
* Glue and shims of any kind
* Tuple struct initializer functions
* Drop code (the `Drop::drop` function is not called directly)
* Drop implementations of types without an explicit `Drop` implementation
@ -20,9 +20,10 @@ without explicit syntax) like coercions, autoderef, autoref and overloaded metho
calls have become explicit casts, deref operations, reference expressions or
concrete function calls.
The [THIR] has datatypes that mirror the [HIR] datatypes, but instead of e.g. `-x`
being a `thir::ExprKind::Neg(thir::Expr)` it is a `thir::ExprKind::Neg(hir::Expr)`.
This shallowness enables the `THIR` to represent all datatypes that [HIR] has, but
The [THIR] has datatypes that mirror the [HIR] datatypes, but the [THIR] is a shallow
wrapper around [HIR]. For example, instead of `-x` being a `thir::ExprKind::Neg(thir::Expr)`
(a deep copy), it is a `thir::ExprKind::Neg(hir::Expr)` (a shallow copy).
This shallowness enables the [THIR] to represent all datatypes that [HIR] has, but
without having to create an in-memory copy of the entire [HIR].
[MIR] lowering will first convert the topmost expression from
[HIR] to [THIR] (in [`rustc_mir_build::thir::cx::expr`]) and then process