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ZalatharZalathar
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Rollup merge of #152284 - Zalathar:bogus-thir-let, r=nnethercote
Avoid a bogus THIR span for `let x = offset_of!(..)` The code that creates spans for THIR `let` statements was doing span endpoint manipulation without checking for inclusion/context, resulting in bogus spans observed in #151693. The incorrect spans are easiest to observe with `-Zunpretty=thir-tree`, but they also cause strange user-facing diagnostics for irrefutable let-else.
2 parents d016a67 + cc3fdc6 commit 1992e71

4 files changed

Lines changed: 56 additions & 11 deletions

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‎compiler/rustc_mir_build/src/thir/cx/block.rs‎

Lines changed: 7 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -75,8 +75,13 @@ impl<'tcx> ThirBuildCx<'tcx> {
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debug!(?pattern);
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let span = match local.init {
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Some(init) => local.span.with_hi(init.span.hi()),
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None => local.span,
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Some(init)
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if let Some(init_span) =
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init.span.find_ancestor_inside_same_ctxt(local.span) =>
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{
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local.span.with_hi(init_span.hi())
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}
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Some(_) | None => local.span,
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};
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let stmt = Stmt {
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kind: StmtKind::Let {

‎tests/ui/span/let-offset-of.rs‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,19 @@
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#![crate_type = "rlib"]
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//@ edition: 2024
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//@ check-pass
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// Using `offset_of` in the RHS of a let-else statement should not produce
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// malformed spans or a blank diagnostic snippet.
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//
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// Regression test for <https://github.com/rust-lang/rust/pull/152284>.
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fn init_to_offset_of() {
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use std::mem::offset_of;
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struct Foo { field: u32 }
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if let x = offset_of!(Foo, field) {}
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//~^ WARN irrefutable `if let` pattern
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let x = offset_of!(Foo, field) else { return; };
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//~^ WARN irrefutable `let...else` pattern
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}

‎tests/ui/span/let-offset-of.stderr‎

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@@ -0,0 +1,21 @@
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warning: irrefutable `if let` pattern
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--> $DIR/let-offset-of.rs:14:8
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|
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LL | if let x = offset_of!(Foo, field) {}
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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|
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= note: this pattern will always match, so the `if let` is useless
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= help: consider replacing the `if let` with a `let`
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= note: `#[warn(irrefutable_let_patterns)]` on by default
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warning: irrefutable `let...else` pattern
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--> $DIR/let-offset-of.rs:17:5
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|
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LL | let x = offset_of!(Foo, field) else { return; };
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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|
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= note: this pattern will always match, so the `else` clause is useless
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= help: consider removing the `else` clause
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warning: 2 warnings emitted
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‎tests/ui/thir-print/offset_of.stdout‎

Lines changed: 9 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -68,7 +68,7 @@ body:
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)
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else_block: None
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hir_id: HirId(DefId(offset_of::concrete).10)
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span: $DIR/offset_of.rs:37:5: 1445:57 (#0)
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span: $DIR/offset_of.rs:37:5: 37:33 (#0)
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}
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}
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Stmt {
@@ -117,7 +117,7 @@ body:
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)
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else_block: None
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hir_id: HirId(DefId(offset_of::concrete).20)
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span: $DIR/offset_of.rs:38:5: 1445:57 (#0)
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span: $DIR/offset_of.rs:38:5: 38:33 (#0)
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}
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}
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Stmt {
@@ -166,7 +166,7 @@ body:
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)
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else_block: None
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hir_id: HirId(DefId(offset_of::concrete).30)
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span: $DIR/offset_of.rs:39:5: 1445:57 (#0)
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span: $DIR/offset_of.rs:39:5: 39:34 (#0)
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}
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}
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Stmt {
@@ -215,7 +215,7 @@ body:
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)
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else_block: None
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hir_id: HirId(DefId(offset_of::concrete).40)
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span: $DIR/offset_of.rs:40:5: 1445:57 (#0)
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span: $DIR/offset_of.rs:40:5: 40:36 (#0)
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}
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}
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Stmt {
@@ -264,7 +264,7 @@ body:
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)
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else_block: None
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hir_id: HirId(DefId(offset_of::concrete).50)
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span: $DIR/offset_of.rs:41:5: 1445:57 (#0)
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span: $DIR/offset_of.rs:41:5: 41:36 (#0)
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}
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}
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]
@@ -864,7 +864,7 @@ body:
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)
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else_block: None
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hir_id: HirId(DefId(offset_of::generic).12)
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span: $DIR/offset_of.rs:45:5: 1445:57 (#0)
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span: $DIR/offset_of.rs:45:5: 45:37 (#0)
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}
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}
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Stmt {
@@ -913,7 +913,7 @@ body:
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)
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else_block: None
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hir_id: HirId(DefId(offset_of::generic).24)
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span: $DIR/offset_of.rs:46:5: 1445:57 (#0)
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span: $DIR/offset_of.rs:46:5: 46:37 (#0)
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}
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}
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Stmt {
@@ -962,7 +962,7 @@ body:
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)
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else_block: None
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hir_id: HirId(DefId(offset_of::generic).36)
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span: $DIR/offset_of.rs:47:5: 1445:57 (#0)
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span: $DIR/offset_of.rs:47:5: 47:37 (#0)
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}
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}
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Stmt {
@@ -1011,7 +1011,7 @@ body:
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)
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else_block: None
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hir_id: HirId(DefId(offset_of::generic).48)
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span: $DIR/offset_of.rs:48:5: 1445:57 (#0)
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span: $DIR/offset_of.rs:48:5: 48:37 (#0)
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}
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}
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]

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