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Aug 24, 2022
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update thir output #1445

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161 changes: 105 additions & 56 deletions src/thir.md
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Original file line number Diff line number Diff line change
Expand Up @@ -47,8 +47,18 @@ which is useful to keep peak memory in check. Having a THIR representation of
all bodies of a crate in memory at the same time would be very heavy.

You can get a debug representation of the THIR by passing the `-Zunpretty=thir-tree` flag
to `rustc`. Here is how a function with just the statement `let x = 1 + 2;` gets represented in
THIR:
to `rustc`.

To demonstrate, let's use the following example:

```rust
fn main() {
let x = 1 + 2;
}
```

Here is how that gets represented in THIR (as of <!-- date-check --> Aug 2022):

```rust,no_run
Thir {
// no match arms
Expand All @@ -57,65 +67,83 @@ Thir {
// expression 0, a literal with a value of 1
Expr {
ty: i32,
temp_lifetime: Some(Node(6)),
temp_lifetime: Some(
Node(1),
),
span: oneplustwo.rs:2:13: 2:14 (#0),
kind: Literal {
literal: Const {
ty: i32,
val: Value(Scalar(0x00000001)),
lit: Spanned {
node: Int(
1,
Unsuffixed,
),
span: oneplustwo.rs:2:13: 2:14 (#0),
},
user_ty: None,
const_id: None,
neg: false,
},
},
// expression 1, scope surronding literal 1
Expr {
ty: i32,
temp_lifetime: Some(Node(6)),
temp_lifetime: Some(
Node(1),
),
span: oneplustwo.rs:2:13: 2:14 (#0),
kind: Scope {
region_scope: Node(1),
lint_level: Explicit(HirId {
owner: DefId(0:3 ~ oneplustwo[6ccc]::main),
local_id: 1,
}),
// reference to expression 0 above
region_scope: Node(3),
lint_level: Explicit(
HirId {
owner: DefId(0:3 ~ oneplustwo[6932]::main),
local_id: 3,
},
),
value: e0,
},
},
// expression 2, literal 2
Expr {
ty: i32,
temp_lifetime: Some(Node(6)),
temp_lifetime: Some(
Node(1),
),
span: oneplustwo.rs:2:17: 2:18 (#0),
kind: Literal {
literal: Const {
ty: i32,
val: Value(Scalar(0x00000002)),
lit: Spanned {
node: Int(
2,
Unsuffixed,
),
span: oneplustwo.rs:2:17: 2:18 (#0),
},
user_ty: None,
const_id: None,
neg: false,
},
},
// expression 3, scope surrounding literal 2
Expr {
ty: i32,
temp_lifetime: Some(Node(6)),
temp_lifetime: Some(
Node(1),
),
span: oneplustwo.rs:2:17: 2:18 (#0),
kind: Scope {
region_scope: Node(2),
lint_level: Explicit(HirId {
owner: DefId(0:3 ~ oneplustwo[6ccc]::main),
local_id: 2,
}),
region_scope: Node(4),
lint_level: Explicit(
HirId {
owner: DefId(0:3 ~ oneplustwo[6932]::main),
local_id: 4,
},
),
// reference to expression 2 above
value: e2,
},
},
// expression 4, represents 1 + 2
Expr {
ty: i32,
temp_lifetime: Some(Node(6)),
temp_lifetime: Some(
Node(1),
),
span: oneplustwo.rs:2:13: 2:18 (#0),
kind: Binary {
op: Add,
Expand All @@ -127,30 +155,38 @@ Thir {
// expression 5, scope surronding expression 4
Expr {
ty: i32,
temp_lifetime: Some(Node(6)),
temp_lifetime: Some(
Node(1),
),
span: oneplustwo.rs:2:13: 2:18 (#0),
kind: Scope {
region_scope: Node(3),
lint_level: Explicit(HirId {
owner: DefId(0:3 ~ oneplustwo[6ccc]::main),
local_id: 3,
}),
region_scope: Node(5),
lint_level: Explicit(
HirId {
owner: DefId(0:3 ~ oneplustwo[6932]::main),
local_id: 5,
},
),
value: e4,
},
},
// expression 6, block around statement
Expr {
ty: (),
temp_lifetime: Some(Node(8)),
temp_lifetime: Some(
Node(9),
),
span: oneplustwo.rs:1:11: 3:2 (#0),
kind: Block {
body: Block {
targeted_by_break: false,
region_scope: Node(7),
region_scope: Node(8),
opt_destruction_scope: None,
span: oneplustwo.rs:1:11: 3:2 (#0),
// reference to statement 0 below
stmts: [ s0 ],
stmts: [
s0,
],
expr: None,
safety_mode: Safe,
},
Expand All @@ -160,25 +196,29 @@ Thir {
Expr {
ty: (),
temp_lifetime: Some(
Node(8),
Node(9),
),
span: oneplustwo.rs:1:11: 3:2 (#0),
kind: Scope {
region_scope: Node(8),
lint_level: Explicit(HirId {
owner: DefId(0:3 ~ oneplustwo[6ccc]::main),
local_id: 8,
}),
region_scope: Node(9),
lint_level: Explicit(
HirId {
owner: DefId(0:3 ~ oneplustwo[6932]::main),
local_id: 9,
},
),
value: e6,
},
},
// destruction scope around expression 7
Expr {
ty: (),
temp_lifetime: Some(Node(8)),
temp_lifetime: Some(
Node(9),
),
span: oneplustwo.rs:1:11: 3:2 (#0),
kind: Scope {
region_scope: Destruction(8),
region_scope: Destruction(9),
lint_level: Inherited,
value: e7,
},
Expand All @@ -188,31 +228,40 @@ Thir {
// let statement
Stmt {
kind: Let {
remainder_scope: Remainder { block: 7, first_statement_index: 0},
init_scope: Node(6),
remainder_scope: Remainder { block: 8, first_statement_index: 0},
init_scope: Node(1),
pattern: Pat {
ty: i32,
span: oneplustwo.rs:2:9: 2:10 (#0),
kind: Binding {
mutability: Not,
name: "x",
mode: ByValue,
var: HirId {
owner: DefId(0:3 ~ oneplustwo[6ccc]::main),
local_id: 5,
},
var: LocalVarId(
HirId {
owner: DefId(0:3 ~ oneplustwo[6932]::main),
local_id: 7,
},
),
ty: i32,
subpattern: None,
is_primary: true,
},
},
initializer: Some(e5),
lint_level: Explicit(HirId {
owner: DefId(0:3 ~ oneplustwo[6ccc]::main),
local_id: 4,
}),
initializer: Some(
e5,
),
else_block: None,
lint_level: Explicit(
HirId {
owner: DefId(0:3 ~ oneplustwo[6932]::main),
local_id: 6,
},
),
},
opt_destruction_scope: Some(Destruction(6)),
opt_destruction_scope: Some(
Destruction(1),
),
},
],
}
Expand Down