coverage: Pass a LocalFileId to CoverageSpan::from_source_region

Author: Zalathar

Diff for: compiler/rustc_codegen_llvm/src/coverageinfo/ffi.rs

@@ -1,5 +1,7 @@
 use rustc_middle::mir::coverage::{CounterId, CovTerm, ExpressionId, SourceRegion};
 
+use crate::coverageinfo::mapgen::LocalFileId;
+
 /// Must match the layout of `LLVMRustCounterKind`.
 #[derive(Copy, Clone, Debug)]
 #[repr(C)]
@@ -137,7 +139,11 @@ pub(crate) struct CoverageSpan {
 }
 
 impl CoverageSpan {
-    pub(crate) fn from_source_region(file_id: u32, code_region: &SourceRegion) -> Self {
+    pub(crate) fn from_source_region(
+        local_file_id: LocalFileId,
+        code_region: &SourceRegion,
+    ) -> Self {
+        let file_id = local_file_id.as_u32();
         let &SourceRegion { start_line, start_col, end_line, end_col } = code_region;
         // Internally, LLVM uses the high bit of `end_col` to distinguish between
         // code regions and gap regions, so it can't be used by the column number.

Diff for: compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs

@@ -210,7 +210,7 @@ rustc_index::newtype_index! {
     /// An index into a function's list of global file IDs. That underlying list
     /// of local-to-global mappings will be embedded in the function's record in
     /// the `__llvm_covfun` linker section.
-    struct LocalFileId {}
+    pub(crate) struct LocalFileId {}
 }
 
 /// Holds a mapping from "local" (per-function) file IDs to "global" (per-CGU)
@@ -280,7 +280,7 @@ fn encode_mappings_for_function(
     // form suitable for FFI.
     for (mapping_kind, region) in counter_regions {
         debug!("Adding counter {mapping_kind:?} to map for {region:?}");
-        let span = ffi::CoverageSpan::from_source_region(local_file_id.as_u32(), region);
+        let span = ffi::CoverageSpan::from_source_region(local_file_id, region);
         match mapping_kind {
             MappingKind::Code(term) => {
                 code_regions.push(ffi::CodeRegion { span, counter: ffi::Counter::from_term(term) });