From c015927af3604ec5305e078c1a57c81901f81190 Mon Sep 17 00:00:00 2001
From: Paul Daniel Faria <Nashenas88@users.noreply.github.com>
Date: Tue, 27 Aug 2019 00:20:21 -0400
Subject: [PATCH 1/3] Fix ICE in rustdoc when merging generic and where bounds
 in the case of an Fn with an output

Fixes #57180
---
 src/librustdoc/clean/simplify.rs | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/librustdoc/clean/simplify.rs b/src/librustdoc/clean/simplify.rs
index 8758ab1969116..2142d6de5da5d 100644
--- a/src/librustdoc/clean/simplify.rs
+++ b/src/librustdoc/clean/simplify.rs
@@ -122,9 +122,9 @@ pub fn merge_bounds(
                     },
                 });
             }
-            PP::Parenthesized { ref mut output, .. } => {
-                assert!(output.is_none());
-                if *rhs != clean::Type::Tuple(Vec::new()) {
+            PP::Parenthesized { ref mut output, .. } => match output {
+                Some(o) => assert!(o == rhs),
+                None => if *rhs != clean::Type::Tuple(Vec::new()) {
                     *output = Some(rhs.clone());
                 }
             }

From 09f6b44790afa924aabf723518931191d92eb472 Mon Sep 17 00:00:00 2001
From: Paul Daniel Faria <Nashenas88@users.noreply.github.com>
Date: Tue, 27 Aug 2019 00:22:31 -0400
Subject: [PATCH 2/3] Simplify some code in rustdoc's simplify

---
 src/librustdoc/clean/simplify.rs | 19 +++++--------------
 1 file changed, 5 insertions(+), 14 deletions(-)

diff --git a/src/librustdoc/clean/simplify.rs b/src/librustdoc/clean/simplify.rs
index 2142d6de5da5d..73bc0386326ce 100644
--- a/src/librustdoc/clean/simplify.rs
+++ b/src/librustdoc/clean/simplify.rs
@@ -35,7 +35,7 @@ pub fn where_clauses(cx: &DocContext<'_>, clauses: Vec<WP>) -> Vec<WP> {
                 match ty {
                     clean::Generic(s) => params.entry(s).or_default()
                                                .extend(bounds),
-                    t => tybounds.push((t, ty_bounds(bounds))),
+                    t => tybounds.push((t, bounds)),
                 }
             }
             WP::RegionPredicate { lifetime, bounds } => {
@@ -45,11 +45,6 @@ pub fn where_clauses(cx: &DocContext<'_>, clauses: Vec<WP>) -> Vec<WP> {
         }
     }
 
-    // Simplify the type parameter bounds on all the generics
-    let mut params = params.into_iter().map(|(k, v)| {
-        (k, ty_bounds(v))
-    }).collect::<BTreeMap<_, _>>();
-
     // Look for equality predicates on associated types that can be merged into
     // general bound predicates
     equalities.retain(|&(ref lhs, ref rhs)| {
@@ -73,7 +68,7 @@ pub fn where_clauses(cx: &DocContext<'_>, clauses: Vec<WP>) -> Vec<WP> {
     // And finally, let's reassemble everything
     let mut clauses = Vec::new();
     clauses.extend(lifetimes.into_iter().map(|(lt, bounds)| {
-        WP::RegionPredicate { lifetime: lt, bounds: bounds }
+        WP::RegionPredicate { lifetime: lt, bounds }
     }));
     clauses.extend(params.into_iter().map(|(k, v)| {
         WP::BoundPredicate {
@@ -82,10 +77,10 @@ pub fn where_clauses(cx: &DocContext<'_>, clauses: Vec<WP>) -> Vec<WP> {
         }
     }));
     clauses.extend(tybounds.into_iter().map(|(ty, bounds)| {
-        WP::BoundPredicate { ty: ty, bounds: bounds }
+        WP::BoundPredicate { ty, bounds }
     }));
     clauses.extend(equalities.into_iter().map(|(lhs, rhs)| {
-        WP::EqPredicate { lhs: lhs, rhs: rhs }
+        WP::EqPredicate { lhs, rhs }
     }));
     clauses
 }
@@ -137,7 +132,7 @@ pub fn ty_params(mut params: Vec<clean::GenericParamDef>) -> Vec<clean::GenericP
     for param in &mut params {
         match param.kind {
             clean::GenericParamDefKind::Type { ref mut bounds, .. } => {
-                *bounds = ty_bounds(mem::take(bounds));
+                *bounds = mem::take(bounds);
             }
             _ => panic!("expected only type parameters"),
         }
@@ -145,10 +140,6 @@ pub fn ty_params(mut params: Vec<clean::GenericParamDef>) -> Vec<clean::GenericP
     params
 }
 
-fn ty_bounds(bounds: Vec<clean::GenericBound>) -> Vec<clean::GenericBound> {
-    bounds
-}
-
 fn trait_is_same_or_supertrait(cx: &DocContext<'_>, child: DefId,
                                trait_: DefId) -> bool {
     if child == trait_ {

From 143b83a3c1e3a03d9795b891e4f2298c5e59f66a Mon Sep 17 00:00:00 2001
From: Paul Daniel Faria <Nashenas88@users.noreply.github.com>
Date: Wed, 28 Aug 2019 00:21:30 -0400
Subject: [PATCH 3/3] Add regression test for issue, apply suggestion to
 convert to assert_eq

---
 src/librustdoc/clean/simplify.rs          |  2 +-
 src/test/rustdoc/auxiliary/issue-57180.rs | 16 ++++++++++++++++
 src/test/rustdoc/issue-57180.rs           |  7 +++++++
 3 files changed, 24 insertions(+), 1 deletion(-)
 create mode 100644 src/test/rustdoc/auxiliary/issue-57180.rs
 create mode 100644 src/test/rustdoc/issue-57180.rs

diff --git a/src/librustdoc/clean/simplify.rs b/src/librustdoc/clean/simplify.rs
index 73bc0386326ce..853170542e083 100644
--- a/src/librustdoc/clean/simplify.rs
+++ b/src/librustdoc/clean/simplify.rs
@@ -118,7 +118,7 @@ pub fn merge_bounds(
                 });
             }
             PP::Parenthesized { ref mut output, .. } => match output {
-                Some(o) => assert!(o == rhs),
+                Some(o) => assert_eq!(o, rhs),
                 None => if *rhs != clean::Type::Tuple(Vec::new()) {
                     *output = Some(rhs.clone());
                 }
diff --git a/src/test/rustdoc/auxiliary/issue-57180.rs b/src/test/rustdoc/auxiliary/issue-57180.rs
new file mode 100644
index 0000000000000..4e2f4b87c020e
--- /dev/null
+++ b/src/test/rustdoc/auxiliary/issue-57180.rs
@@ -0,0 +1,16 @@
+// compile-flags: -Cmetadata=aux
+
+pub trait Trait {
+}
+
+pub struct Struct<F>
+{
+    _p: ::std::marker::PhantomData<F>,
+}
+
+impl<F: Fn() -> u32>
+Trait for Struct<F>
+    where
+        F: Fn() -> u32,
+{
+}
diff --git a/src/test/rustdoc/issue-57180.rs b/src/test/rustdoc/issue-57180.rs
new file mode 100644
index 0000000000000..14bd2b0fec0d5
--- /dev/null
+++ b/src/test/rustdoc/issue-57180.rs
@@ -0,0 +1,7 @@
+// aux-build:issue-57180.rs
+
+extern crate issue_57180;
+use issue_57180::Trait;
+
+fn main() {
+}