Merge pull request #195 from fiddlerwoaroof/wire2/59q8

Source scanner: bound test-only items by brackets, evaluate cfg predicates (59q8)

context/test-evidence/protocol.md

@@ -1050,3 +1050,51 @@ Faults injected, one per half, each compiling only `improvise-protocol`:
 A field added to an existing variant is caught too, but not in isolation,
 because every constructor of that variant also fails. Reverted with
 `git restore`.
+
+### source_scan::tests::a_test_only_item_hides_nothing_after_it
+
+improvise-59q8, found by the PR #172 review. The scanner's line-based
+`strip_test_items` looked for `}` at the attribute's indentation, or for an item
+line ending in `;`. So three shapes were never bounded, and it dropped
+**everything to the end of the file**:
+- a test-only `const … = &[\n … \n];`;
+- a `#[cfg(test)] let x = foo(\n 1,\n);` statement;
+- a one-line `#[cfg(test)] use foo::bar;`, where the attribute's own line is
+  also the item line.
+
+In `vocabulary_is_complete` that silently hides every effect after such an
+item. Each shape is a case here, asserting that the production code after it
+(`Hidden1`, `Visible`) survives. Against the line scan all three failed; the
+first printed `"impl X {\n"` and nothing else. They now pass because items are
+bounded by balanced brackets on the blanked code.
+`an_unbounded_test_only_item_is_refused_not_swallowed` pins the other half of
+the acceptance criteria: an item that cannot be bounded panics instead of
+consuming the rest of the file. Against the line scan it failed, because
+nothing panicked.
+
+### source_scan::tests::a_test_only_cfg_is_recognised_whatever_its_spelling
+
+improvise-59q8, the other direction: test code counted as production, which
+makes `vocabulary_is_composed` weaker. `cfg(all(test, not(target_arch =
+"wasm32")))` was kept because the old rule rejected any line containing
+`not(`. A leading `#![cfg(test)]` was kept because only `#[cfg(` was
+recognised. An attribute split across lines was not seen at all. All three
+failed against the old scanner. The predicate is now parsed and evaluated in
+three-valued logic (`context/code/protocol.md` §2). The controls
+(`cfg(not(test))`, `cfg(any(test, feature = "serde"))` and `cfg(target_arch =
+…)`) must stay production, so a scanner that dropped every `cfg` item could
+not pass.
+
+A consequence to know about: `cfg(any(test, feature = "x"))` for an ordinary
+feature is now production. Only `feature = "test-support"`, the one test
+feature this repo has, counts as a test build.
+`test_only_items_and_modules_are_not_production` was updated to that spelling.
+
+### source_scan::tests::a_c_string_literal_is_blanked
+
+improvise-59q8's minor case. In `cr#"x" Command::InRawC(2) "y"#` the `r` has a
+word character before it, so the literal was lexed as two ordinary strings,
+and the text between the inner quotes leaked. It failed as
+`InRawC survived`. `c"…"` and `cr#"…"#` are now literals. A first version of
+this test used a C string with no inner quotes and passed against the bug,
+because the ordinary lexing happened to blank it too.