coverage. Refactor MCDCInfoBuilder for pattern matching implementation and change the way to calculate decision depth

Author: zhuyunxing

compiler/rustc_middle/src/mir/coverage.rs

@@ -50,7 +50,6 @@ rustc_index::newtype_index! {
     #[debug_format = "ExpressionId({})"]
     pub struct ExpressionId {}
 }
-
 rustc_index::newtype_index! {
     /// ID of a mcdc condition. Used by llvm to check mcdc coverage.
     ///
@@ -332,3 +331,9 @@ pub struct MCDCDecisionSpan {
     pub end_markers: Vec<BlockMarkerId>,
     pub decision_depth: u16,
 }
+
+impl MCDCDecisionSpan {
+    pub fn new(span: Span) -> Self {
+        Self { span, num_conditions: 0, end_markers: Vec::new(), decision_depth: 0 }
+    }
+}

compiler/rustc_mir_build/src/build/coverageinfo.rs

@@ -144,10 +144,10 @@ impl CoverageInfoBuilder {
         // Separate path for handling branches when MC/DC is enabled.
         if let Some(mcdc_info) = self.mcdc_info.as_mut() {
             let inject_block_marker =
-                |source_info, block| self.markers.inject_block_marker(cfg, source_info, block);
+                |block| self.markers.inject_block_marker(cfg, source_info, block);
             mcdc_info.visit_evaluated_condition(
                 tcx,
-                source_info,
+                source_info.span,
                 true_block,
                 false_block,
                 inject_block_marker,
@@ -175,8 +175,13 @@ impl CoverageInfoBuilder {
         let branch_spans =
             branch_info.map(|branch_info| branch_info.branch_spans).unwrap_or_default();
 
-        let (mcdc_decision_spans, mcdc_branch_spans) =
+        let (mut mcdc_branch_spans, mcdc_spans) =
             mcdc_info.map(MCDCInfoBuilder::into_done).unwrap_or_default();
+        let mut mcdc_decision_spans = Vec::with_capacity(mcdc_spans.len());
+        for (decision, conditions) in mcdc_spans {
+            mcdc_branch_spans.extend(conditions);
+            mcdc_decision_spans.push(decision);
+        }
 
         // For simplicity, always return an info struct (without Option), even
         // if there's nothing interesting in it.