Update CI for trybuild

This avoids running UI tests except in code coverage generation, as the
output of UI tests can vary by compiler.

.github/workflows/build.yaml

@@ -214,16 +214,6 @@ jobs:
         with:
           command: test
           args: --all-features
-        if: matrix.os.name == 'Ubuntu'
-
-      - name: Test
-        uses: actions-rs/cargo@v1
-        with:
-          command: test
-          args: --all-features
-        env:
-          RUSTFLAGS: "--cfg skip_ui_tests"
-        if: matrix.os.name != 'Ubuntu'
 
   fmt:
     name: Formatting
@@ -363,10 +353,12 @@ jobs:
           curl -LsSf https://github.com/taiki-e/cargo-llvm-cov/releases/download/v0.1.0-alpha.5/cargo-llvm-cov-x86_64-unknown-linux-gnu.tar.gz | tar xzf - -C ~/.cargo/bin
 
       - name: Generate coverage report
-        run: cargo llvm-cov --all-features --lcov > lcov.txt
+        run: cargo llvm-cov --all-features --workspace --lcov > lcov.txt
+        env:
+          # Don't run these anywhere else as the results can depend on the exact compiler used.
+          RUSTFLAGS: "--cfg __ui_tests"
 
       - name: Upload coverage report
         uses: codecov/codecov-action@v1
         with:
           files: ./lcov.txt
-          fail_ci_if_error: false

Cargo.toml

@@ -50,6 +50,8 @@ criterion = { version = "0.3.5", features = ["html_reports"] }
 rand = { version = "0.8.4", default-features = false }
 serde = { version = "1.0.126", default-features = false }
 serde_test = "1.0.126"
+
+[target.'cfg(__ui_tests)'.dev-dependencies]
 trybuild = "1.0.44"
 
 # Significant contributions to the benchmarks provided by Emil Lundberg.

tests/integration/main.rs

@@ -41,8 +41,6 @@
     clippy::cmp_owned
 )]
 
-use trybuild::TestCases;
-
 /// Construct a non-exhaustive modifier.
 macro_rules! modifier {
     ($name:ident {
@@ -79,8 +77,9 @@ mod utc_offset;
 mod util;
 mod weekday;
 
+#[cfg(__ui_tests)]
 #[test]
 fn compile_fail() {
-    let tests = TestCases::new();
+    let tests = trybuild::TestCases::new();
     tests.compile_fail("tests/integration/compile-fail/*.rs");
 }