Fix ICE #103748

compiler/rustc_middle/src/values.rs

@@ -185,7 +185,8 @@ fn find_item_ty_spans(
                 });
                 if check_params && let Some(args) = path.segments.last().unwrap().args {
                     let params_in_repr = tcx.params_in_repr(def_id);
-                    for (i, arg) in args.args.iter().enumerate() {
+                    // the domain size check is needed because the HIR may not be well-formed at this point
+                    for (i, arg) in args.args.iter().enumerate().take(params_in_repr.domain_size()) {
                         if let hir::GenericArg::Type(ty) = arg && params_in_repr.contains(i as u32) {
                             find_item_ty_spans(tcx, ty, needle, spans, seen_representable);
                         }

src/test/ui/parser/issue-103748-ICE-wrong-braces.rs

@@ -0,0 +1,8 @@
+#![crate_type = "lib"]
+
+struct Apple((Apple, Option(Banana ? Citron)));
+//~^ ERROR invalid `?` in type
+//~| ERROR expected one of `)` or `,`, found `Citron`
+//~| ERROR cannot find type `Citron` in this scope [E0412]
+//~| ERROR parenthesized type parameters may only be used with a `Fn` trait [E0214]
+//~| ERROR recursive type `Apple` has infinite size [E0072]

src/test/ui/parser/issue-103748-ICE-wrong-braces.stderr

@@ -0,0 +1,51 @@
+error: invalid `?` in type
+  --> $DIR/issue-103748-ICE-wrong-braces.rs:3:36
+   |
+LL | struct Apple((Apple, Option(Banana ? Citron)));
+   |                                    ^ `?` is only allowed on expressions, not types
+   |
+help: if you meant to express that the type might not contain a value, use the `Option` wrapper type
+   |
+LL | struct Apple((Apple, Option(Option<Banana > Citron)));
+   |                             +++++++       ~
+
+error: expected one of `)` or `,`, found `Citron`
+  --> $DIR/issue-103748-ICE-wrong-braces.rs:3:38
+   |
+LL | struct Apple((Apple, Option(Banana ? Citron)));
+   |                                     -^^^^^^ expected one of `)` or `,`
+   |                                     |
+   |                                     help: missing `,`
+
+error[E0412]: cannot find type `Citron` in this scope
+  --> $DIR/issue-103748-ICE-wrong-braces.rs:3:38
+   |
+LL | struct Apple((Apple, Option(Banana ? Citron)));
+   |                                      ^^^^^^ not found in this scope
+
+error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
+  --> $DIR/issue-103748-ICE-wrong-braces.rs:3:22
+   |
+LL | struct Apple((Apple, Option(Banana ? Citron)));
+   |                      ^^^^^^^^^^^^^^^^^^^^^^^ only `Fn` traits may use parentheses
+   |
+help: use angle brackets instead
+   |
+LL | struct Apple((Apple, Option<Banana ? Citron>));
+   |                            ~               ~
+
+error[E0072]: recursive type `Apple` has infinite size
+  --> $DIR/issue-103748-ICE-wrong-braces.rs:3:1
+   |
+LL | struct Apple((Apple, Option(Banana ? Citron)));
+   | ^^^^^^^^^^^^  ----- recursive without indirection
+   |
+help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to break the cycle
+   |
+LL | struct Apple((Box<Apple>, Option(Banana ? Citron)));
+   |               ++++     +
+
+error: aborting due to 5 previous errors
+
+Some errors have detailed explanations: E0072, E0214, E0412.
+For more information about an error, try `rustc --explain E0072`.