check: refuse a module that declares a top-level name twice (Closes #10421)

bootstrap/src/compiler.rs

@@ -25528,12 +25528,15 @@ fn collect_top_level_decls(node: &Node, out: &mut Vec<(String, &'static str)>) {
 fn duplicate_top_level_decls(ast: &Node) -> Vec<DuplicateDecl> {
     let mut decls: Vec<(String, &'static str)> = Vec::new();
     collect_top_level_decls(ast, &mut decls);
+    for c in ast.children.iter().filter(|c| c.kind == NodeKind::ConstDecl) { // module level only: a local `const` is scope
+        decls.push((c.name.clone(), if c.extra_mutable { "var" } else { "const" }));
+    }
     // Four namespaces, not two. A test name collides only with another test
     // name: `struct deque_clear` beside `test deque_clear` is not a conflict
     // in any backend, and 138 names across 54 specs are exactly that shape.
     // Folding tests into "type" would report every one of them.
     let ns = |k: &str| match k {
-        "fn" => "value",
+        "fn" | "const" | "var" => "value",
         "test" => "test",
         "bench" => "bench",
         _ => "type",
@@ -25772,6 +25775,13 @@ drop the parameter from the declaration and keep it at each use, where it is und
     }
 
     for d in duplicate_top_level_decls(ast) {
+        if let DuplicateDecl::SameNamespace(name, kind, n) = &d { // an error, as E_NAME is in the self-hosted core (#10421); a bench stays a warning
+            if *kind != "bench" {
+                result.error_count += 1;
+                result.errors.push(format!("error: `{kind} {name}` is declared {n} times -- every backend rejects a redeclaration (gen-js kept the first copy, gen-c the last, before check refused it)"));
+                continue;
+            }
+        }
         let msg = match d {
             DuplicateDecl::SameNamespace(name, kind, n) => format!(
                 "warning: `{kind} {name}` is declared {n} times -- every backend rejects a redeclaration"

bootstrap/stage0/FROZEN_HASH

@@ -1 +1 @@
-fad12492937aa2196d2adbf560305e367f5dd1183a3107137d5bc0c1c26033ab bootstrap/src/compiler.rs
+092ec34c7ce7592ab4a5124277a8cc4c5852d358874af8fa5a96ae991f41b655 bootstrap/src/compiler.rs

bootstrap/tests/duplicate_declarations.rs

@@ -40,26 +40,28 @@ const DUP_STRUCT: &str = r#"
 module D1 {
     struct A { x : i32, }
     struct A { y : i32, }
+    const K : i32 = 1; const K : i32 = 2;
     fn f(a: A) -> i32 { return a.x; }
 }
 "#;
 
 const CLEAN: &str = r#"
 module D3 {
     struct C { x : i32, }
-    fn g(c: C) -> i32 { return c.x; }
+    fn g(c: C) -> i32 { const K : i32 = 1; return c.x + K; }
+    fn h(c: C) -> i32 { const K : i32 = 2; return c.x + K; }
 }
 "#;
 
 #[test]
 fn a_name_declared_twice_is_reported_with_its_count() {
     let (_, out) = check(DUP_STRUCT, "twice");
     assert!(
-        out.contains("`struct A` is declared 2 times"),
+        out.contains("`struct A` is declared 2 times") && out.contains("`const K` is declared 2 times"),
         "the finding must name the kind, the name and the count:\n{out}"
     );
     assert!(
-        out.contains("every backend rejects a redeclaration"),
+        out.contains("error: ") && out.contains("every backend rejects a redeclaration"),
         "and say what the consequence is:\n{out}"
     );
 }
@@ -119,23 +121,11 @@ module D4 {
         "structenum",
     );
     assert!(
-        out.contains("is declared 2 times") && out.contains("every backend rejects"),
+        out.contains("is declared 2 times") && out.contains("error: "),
         "struct and enum sharing a name is a same-namespace collision:\n{out}"
     );
 }
 
-#[test]
-fn the_finding_is_a_warning_and_does_not_change_the_exit_code() {
-    // Measured over the corpus before this landed: 651 specs, 573 exit 0 and
-    // 78 exit 1, and not one spec's code moved. Pinned here so a later change
-    // to an error is a deliberate, test-visible decision.
-    let (rc, out) = check(DUP_STRUCT, "exitcode");
-    assert_eq!(
-        rc, 0,
-        "the duplicate finding is a warning; promoting it must be deliberate:\n{out}"
-    );
-}
-
 // ---------------------------------------------------------------------------
 // A test block is a declaration too (#3479)
 //

bootstrap/tests/fixtures/duplicate_toplevel/accept/sibling_blocks.t27

@@ -0,0 +1,30 @@
+// Sibling blocks reuse a name: that is scope, not a redeclaration. The same
+// names are used as locals in two functions and in two tests, and a test shares
+// the name of a function (separate namespaces).
+module SiblingBlocks;
+
+pub const LIMIT : u32 = 25;
+
+pub fn first() -> u32 {
+    const limit : u32 = 1;
+    var acc : u32 = 0;
+    acc = acc + limit;
+    return acc;
+}
+
+pub fn second() -> u32 {
+    const limit : u32 = 2;
+    var acc : u32 = 0;
+    acc = acc + limit;
+    return acc;
+}
+
+test "first" {
+    const limit : u32 = 1;
+    assert first() == limit;
+}
+
+test "second" {
+    const limit : u32 = 2;
+    assert second() == limit;
+}

bootstrap/tests/fixtures/duplicate_toplevel/refuse/dup_const.t27

@@ -0,0 +1,6 @@
+// A module const declared twice: gen-js keeps the first value (25), gen-c
+// reads the last (100), and `check` used to say nothing (#10421).
+module DupConst;
+
+pub const LIMIT : u32 = 25;
+pub const LIMIT : u32 = 100;

bootstrap/tests/fixtures/duplicate_toplevel/refuse/dup_const_and_fn.t27

@@ -0,0 +1,28 @@
+module DupProbe;
+
+pub const LIMIT : u32 = 25;
+pub const LIMIT : u32 = 100;
+
+pub fn pick() -> u32 {
+    return 1;
+}
+
+pub fn pick() -> u32 {
+    return 2;
+}
+
+test "the first LIMIT" {
+    assert LIMIT == 25;
+}
+
+test "the last LIMIT" {
+    assert LIMIT == 100;
+}
+
+test "the first pick" {
+    assert pick() == 1;
+}
+
+test "the last pick" {
+    assert pick() == 2;
+}

bootstrap/tests/fixtures/duplicate_toplevel/refuse/dup_fn.t27

@@ -0,0 +1,10 @@
+// A function declared twice.
+module DupFn;
+
+pub fn pick() -> u32 {
+    return 1;
+}
+
+pub fn pick() -> u32 {
+    return 2;
+}

bootstrap/tests/fixtures/duplicate_toplevel/refuse/dup_struct.t27

@@ -0,0 +1,10 @@
+// A struct declared twice.
+module DupStruct;
+
+pub struct Pair {
+    lo: u32,
+}
+
+pub struct Pair {
+    hi: u32,
+}

bootstrap/tests/fixtures/duplicate_toplevel/refuse/dup_test.t27

@@ -0,0 +1,14 @@
+// A test block declared twice under one name.
+module DupTest;
+
+pub fn one() -> u32 {
+    return 1;
+}
+
+test "same name" {
+    assert one() == 1;
+}
+
+test "same name" {
+    assert one() == 1;
+}

bootstrap/tests/fixtures/duplicate_toplevel/refuse/dup_var.t27

@@ -0,0 +1,5 @@
+// A module var declared twice.
+module DupVar;
+
+var counter : u32 = 0;
+var counter : u32 = 1;

tools/specs_generate_baseline.txt

@@ -25,3 +25,14 @@ bootstrap/tests/fixtures/core_selfhost/refuse/e16_compound_cross_sign.t27 | Erro
 bootstrap/tests/fixtures/core_selfhost/refuse/e16_const_too_wide.t27 | Error: typecheck refused bootstrap/tests/fixtures/core_selfhost/refuse/e16_const_too_wide.t27: 1 error(s), so nothing is generated for it (#6446)
 bootstrap/tests/fixtures/core_selfhost/refuse/e16_const_too_wide_signed.t27 | Error: typecheck refused bootstrap/tests/fixtures/core_selfhost/refuse/e16_const_too_wide_signed.t27: 1 error(s), so nothing is generated for it (#644
 bootstrap/tests/fixtures/core_selfhost/refuse/e4_arity_return.t27 | Error: typecheck refused bootstrap/tests/fixtures/core_selfhost/refuse/e4_arity_return.t27: 1 error(s), so nothing is generated for it (#6446)
+# Not a debt: #10421's refuse fixtures. A duplicated top-level name is now a typecheck error, so no backend generates them; the self-hosted core refuses the same names with E_NAME.
+bootstrap/tests/fixtures/core_selfhost/refuse/e5_duplicate_const.t27 | Error: typecheck refused bootstrap/tests/fixtures/core_selfhost/refuse/e5_duplicate_const.t27: 1 error(s), so nothing is generated for it (#6446)
+bootstrap/tests/fixtures/core_selfhost/refuse/e5_duplicate_fn.t27 | Error: typecheck refused bootstrap/tests/fixtures/core_selfhost/refuse/e5_duplicate_fn.t27: 1 error(s), so nothing is generated for it (#6446)
+bootstrap/tests/fixtures/core_selfhost/refuse/e5_duplicate_test.t27 | Error: typecheck refused bootstrap/tests/fixtures/core_selfhost/refuse/e5_duplicate_test.t27: 1 error(s), so nothing is generated for it (#6446)
+bootstrap/tests/fixtures/core_selfhost/refuse/e5_var_and_fn_one_name.t27 | Error: typecheck refused bootstrap/tests/fixtures/core_selfhost/refuse/e5_var_and_fn_one_name.t27: 1 error(s), so nothing is generated for it (#6446)
+bootstrap/tests/fixtures/duplicate_toplevel/refuse/dup_const.t27 | Error: typecheck refused bootstrap/tests/fixtures/duplicate_toplevel/refuse/dup_const.t27: 1 error(s), so nothing is generated for it (#6446)
+bootstrap/tests/fixtures/duplicate_toplevel/refuse/dup_const_and_fn.t27 | Error: typecheck refused bootstrap/tests/fixtures/duplicate_toplevel/refuse/dup_const_and_fn.t27: 2 error(s), so nothing is generated for it (#6446)
+bootstrap/tests/fixtures/duplicate_toplevel/refuse/dup_fn.t27 | Error: typecheck refused bootstrap/tests/fixtures/duplicate_toplevel/refuse/dup_fn.t27: 1 error(s), so nothing is generated for it (#6446)
+bootstrap/tests/fixtures/duplicate_toplevel/refuse/dup_struct.t27 | Error: typecheck refused bootstrap/tests/fixtures/duplicate_toplevel/refuse/dup_struct.t27: 1 error(s), so nothing is generated for it (#6446)
+bootstrap/tests/fixtures/duplicate_toplevel/refuse/dup_test.t27 | Error: typecheck refused bootstrap/tests/fixtures/duplicate_toplevel/refuse/dup_test.t27: 1 error(s), so nothing is generated for it (#6446)
+bootstrap/tests/fixtures/duplicate_toplevel/refuse/dup_var.t27 | Error: typecheck refused bootstrap/tests/fixtures/duplicate_toplevel/refuse/dup_var.t27: 1 error(s), so nothing is generated for it (#6446)