Improve spans in custom mir

compiler/rustc_mir_build/src/build/custom/mod.rs

@@ -74,7 +74,7 @@ pub(super) fn build_custom_mir<'tcx>(
     let mut pctxt = ParseCtxt {
         tcx,
         thir,
-        source_info: SourceInfo { span, scope: OUTERMOST_SOURCE_SCOPE },
+        source_scope: OUTERMOST_SOURCE_SCOPE,
         body: &mut body,
         local_map: FxHashMap::default(),
         block_map: FxHashMap::default(),
@@ -128,7 +128,7 @@ fn parse_attribute(attr: &Attribute) -> MirPhase {
 struct ParseCtxt<'tcx, 'body> {
     tcx: TyCtxt<'tcx>,
     thir: &'body Thir<'tcx>,
-    source_info: SourceInfo,
+    source_scope: SourceScope,
 
     body: &'body mut Body<'tcx>,
     local_map: FxHashMap<LocalVarId, Local>,

compiler/rustc_mir_build/src/build/custom/parse.rs

@@ -233,15 +233,23 @@ impl<'tcx, 'body> ParseCtxt<'tcx, 'body> {
         let mut data = BasicBlockData::new(None);
         for stmt_id in &*block.stmts {
             let stmt = self.statement_as_expr(*stmt_id)?;
+            let span = self.thir[stmt].span;
             let statement = self.parse_statement(stmt)?;
-            data.statements.push(Statement { source_info: self.source_info, kind: statement });
+            data.statements.push(Statement {
+                source_info: SourceInfo { span, scope: self.source_scope },
+                kind: statement,
+            });
         }
 
         let Some(trailing) = block.expr else {
             return Err(self.expr_error(expr_id, "terminator"))
         };
+        let span = self.thir[trailing].span;
         let terminator = self.parse_terminator(trailing)?;
-        data.terminator = Some(Terminator { source_info: self.source_info, kind: terminator });
+        data.terminator = Some(Terminator {
+            source_info: SourceInfo { span, scope: self.source_scope },
+            kind: terminator,
+        });
 
         Ok(data)
     }

compiler/rustc_mir_build/src/build/mod.rs

@@ -492,7 +492,7 @@ fn construct_fn<'tcx>(
             arguments,
             return_ty,
             return_ty_span,
-            span,
+            span_with_body,
             custom_mir_attr,
         );
     }