Add coverage support (fixes #5)

.github/actions-rs/grcov.yml

@@ -0,0 +1,2 @@
+output-type: lcov
+output-file: ./lcov.info

.github/workflows/ci.yml

@@ -10,16 +10,31 @@ jobs:
           - { rust: stable }
     steps:
       - uses: actions/checkout@v3
-      - uses: actions-rs/toolchain@v1
+      - uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ matrix.rust }}
-          override: true
       - name: Build
         run: cargo build
       - name: Test
         run: cargo test
-#        if: ${{ contains(matrix.features, 'coverage') }}
-#        uses: codecov/codecov-action@v3
-#        with:
-#          fail_ci_if_error: true
-#          gcov: true
+
+  coverage:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: nightly
+      - name: Test
+        run: cargo test
+        env:
+          RUSTFLAGS: '-Zprofile -Ccodegen-units=1 -Cinline-threshold=0 -Clink-dead-code -Coverflow-checks=off -Cpanic=abort -Zpanic_abort_tests'
+          RUSTDOCFLAGS: '-Zprofile -Ccodegen-units=1 -Cinline-threshold=0 -Clink-dead-code -Coverflow-checks=off -Cpanic=abort -Zpanic_abort_tests'
+      - name: Collect coverage
+        uses: actions-rs/[email protected]
+      - name: Submit coverage
+        uses: codecov/codecov-action@v4-beta
+        with:
+          fail_ci_if_error: true
+        env:
+          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}