Add tests

compiler/rustc_typeck/src/coherence/inherent_impls_overlap.rs

@@ -140,7 +140,8 @@ impl ItemLikeVisitor<'v> for InherentOverlapChecker<'tcx> {
                 // Perform a O(n^2) algorithm for small n,
                 // otherwise switch to an allocating algorithm with
                 // faster asymptotic runtime.
-                if impls.len() < 30 {
+                const ALLOCATING_ALGO_THRESHOLD: usize = 500;
+                if impls.len() < ALLOCATING_ALGO_THRESHOLD {
                     for (i, &(&impl1_def_id, impl_items1)) in impls_items.iter().enumerate() {
                         for &(&impl2_def_id, impl_items2) in &impls_items[(i + 1)..] {
                             if self.impls_have_common_items(impl_items1, impl_items2) {

src/test/ui/inherent-impls-overlap-check/auxiliary/repeat.rs

@@ -0,0 +1,54 @@
+// force-host
+// no-prefer-dynamic
+
+#![crate_type = "proc-macro"]
+
+extern crate proc_macro;
+use proc_macro::{Ident, Group, TokenStream, TokenTree as Tt};
+
+// This constant has to be above the ALLOCATING_ALGO_THRESHOLD
+// constant in inherent_impls_overlap.rs
+const REPEAT_COUNT: u32 = 501;
+
+#[proc_macro]
+/// Repeats the input many times, while replacing idents
+/// named "IDENT" with "id_$v", where v is a counter.
+pub fn repeat_with_idents(input: TokenStream) -> TokenStream {
+    let mut res = Vec::new();
+    fn visit_stream(res: &mut Vec<Tt>, stream :TokenStream, v: u32) {
+        let mut stream_iter = stream.into_iter();
+        while let Some(tt) = stream_iter.next() {
+            match tt {
+                Tt::Group(group) => {
+                    let tt = Tt::Group(visit_group(group, v));
+                    res.push(tt);
+                },
+                Tt::Ident(id) => {
+                    let id = if &id.to_string() == "IDENT" {
+                        Ident::new(&format!("id_{}", v), id.span())
+                    } else {
+                        id
+                    };
+                    res.push(Tt::Ident(id));
+                },
+                Tt::Punct(p) => {
+                    res.push(Tt::Punct(p));
+                },
+                Tt::Literal(lit) => {
+                    res.push(Tt::Literal(lit));
+                },
+            }
+        }
+    }
+    fn visit_group(group :Group, v: u32) -> Group {
+        let mut res = Vec::new();
+        visit_stream(&mut res, group.stream(), v);
+        let stream = res.into_iter().collect();
+        let delim = group.delimiter();
+        Group::new(delim, stream)
+    }
+    for v in 0 .. REPEAT_COUNT {
+        visit_stream(&mut res, input.clone(), v)
+    }
+    res.into_iter().collect()
+}

src/test/ui/inherent-impls-overlap-check/no-overlap.rs

@@ -0,0 +1,34 @@
+// run-pass
+// aux-build:repeat.rs
+
+// This tests the allocating algo branch of the
+// inherent impls overlap checker.
+// This branch was added by PR:
+// https://github.com/rust-lang/rust/pull/78317
+// In this test, we repeat many impl blocks
+// to trigger the allocating branch.
+
+#![allow(unused)]
+
+extern crate repeat;
+
+// Simple case where each impl block is distinct
+
+struct Foo {}
+
+repeat::repeat_with_idents!(impl Foo { fn IDENT() {} });
+
+// There are overlapping impl blocks but due to generics,
+// they may overlap.
+
+struct Bar<T>(T);
+
+struct A;
+struct B;
+
+repeat::repeat_with_idents!(impl Bar<A> { fn IDENT() {} });
+
+impl Bar<A> { fn foo() {} }
+impl Bar<B> { fn foo() {} }
+
+fn main() {}

src/test/ui/inherent-impls-overlap-check/overlap.rs

@@ -0,0 +1,71 @@
+// aux-build:repeat.rs
+
+#![allow(unused)]
+
+// This tests the allocating algo branch of the
+// inherent impls overlap checker.
+// This branch was added by PR:
+// https://github.com/rust-lang/rust/pull/78317
+// In this test, we repeat many impl blocks
+// to trigger the allocating branch.
+
+// Simple overlap
+
+extern crate repeat;
+
+struct Foo {}
+
+repeat::repeat_with_idents!(impl Foo { fn IDENT() {} });
+
+impl Foo { fn hello() {} } //~ERROR duplicate definitions with name `hello`
+impl Foo { fn hello() {} }
+
+// Transitive overlap
+
+struct Foo2 {}
+
+repeat::repeat_with_idents!(impl Foo2 { fn IDENT() {} });
+
+impl Foo2 {
+    fn bar() {}
+    fn hello2() {} //~ERROR duplicate definitions with name `hello2`
+}
+
+impl Foo2 {
+    fn baz() {}
+    fn hello2() {}
+}
+
+// Slightly stronger transitive overlap
+
+struct Foo3 {}
+
+repeat::repeat_with_idents!(impl Foo3 { fn IDENT() {} });
+
+impl Foo3 {
+    fn bar() {} //~ERROR duplicate definitions with name `bar`
+    fn hello3() {} //~ERROR duplicate definitions with name `hello3`
+}
+
+impl Foo3 {
+    fn bar() {}
+    fn hello3() {}
+}
+
+// Generic overlap
+
+struct Bar<T>(T);
+
+struct A;
+struct B;
+
+repeat::repeat_with_idents!(impl Bar<A> { fn IDENT() {} });
+
+impl Bar<A> { fn foo() {} fn bar2() {} }
+impl Bar<B> {
+    fn foo() {}
+    fn bar2() {} //~ERROR duplicate definitions with name `bar2`
+}
+impl Bar<B> { fn bar2() {} }
+
+fn main() {}

src/test/ui/inherent-impls-overlap-check/overlap.stderr

@@ -0,0 +1,47 @@
+error[E0592]: duplicate definitions with name `hello`
+  --> $DIR/overlap.rs:20:12
+   |
+LL | impl Foo { fn hello() {} }
+   |            ^^^^^^^^^^ duplicate definitions for `hello`
+LL | impl Foo { fn hello() {} }
+   |            ---------- other definition for `hello`
+
+error[E0592]: duplicate definitions with name `hello2`
+  --> $DIR/overlap.rs:31:5
+   |
+LL |     fn hello2() {}
+   |     ^^^^^^^^^^^ duplicate definitions for `hello2`
+...
+LL |     fn hello2() {}
+   |     ----------- other definition for `hello2`
+
+error[E0592]: duplicate definitions with name `bar`
+  --> $DIR/overlap.rs:46:5
+   |
+LL |     fn bar() {}
+   |     ^^^^^^^^ duplicate definitions for `bar`
+...
+LL |     fn bar() {}
+   |     -------- other definition for `bar`
+
+error[E0592]: duplicate definitions with name `hello3`
+  --> $DIR/overlap.rs:47:5
+   |
+LL |     fn hello3() {}
+   |     ^^^^^^^^^^^ duplicate definitions for `hello3`
+...
+LL |     fn hello3() {}
+   |     ----------- other definition for `hello3`
+
+error[E0592]: duplicate definitions with name `bar2`
+  --> $DIR/overlap.rs:67:5
+   |
+LL |     fn bar2() {}
+   |     ^^^^^^^^^ duplicate definitions for `bar2`
+LL | }
+LL | impl Bar<B> { fn bar2() {} }
+   |               --------- other definition for `bar2`
+
+error: aborting due to 5 previous errors
+
+For more information about this error, try `rustc --explain E0592`.