Suggest calling associated `fn` inside `trait`s

When calling a function that doesn't exist inside of a trait's
associated `fn`, and another associated `fn` in that trait has that
name, suggest calling it with the appropriate fully-qualified path.

Expand the label to be more descriptive.

Prompted by the following user experience:
https://users.rust-lang.org/t/cannot-find-function/50663

7 files changed, 69 insertions, 22 deletions

diff --git a/src/test/ui/resolve/associated-fn-called-as-fn.rs b/src/test/ui/resolve/associated-fn-called-as-fn.rs
new file mode 100644
index 00000000000..f31f3d67b5b
--- /dev/null
+++ b/src/test/ui/resolve/associated-fn-called-as-fn.rs
@@ -0,0 +1,32 @@
+struct S;
+impl Foo for S {
+    fn parse(s:&str) {
+        for c in s.chars() {
+            match c {
+                '0'..='9' => collect_primary(&c), //~ ERROR cannot find function `collect_primary`
+                //~^ HELP you might have meant to call the associated function
+                '+' | '-' => println!("We got a sign: {}", c),
+                _ => println!("Not a number!")
+            }
+        }
+    }
+}
+trait Foo {
+    fn collect_primary(ch:&char) { }
+    fn parse(s:&str);
+}
+trait Bar {
+    fn collect_primary(ch:&char) { }
+    fn parse(s:&str) {
+        for c in s.chars() {
+            match c {
+                '0'..='9' => collect_primary(&c), //~ ERROR cannot find function `collect_primary`
+                //~^ HELP you might have meant to call the associated function
+                '+' | '-' => println!("We got a sign: {}", c),
+                _ => println!("Not a number!")
+            }
+        }
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/resolve/associated-fn-called-as-fn.stderr b/src/test/ui/resolve/associated-fn-called-as-fn.stderr
new file mode 100644
index 00000000000..fbdea30d551
--- /dev/null
+++ b/src/test/ui/resolve/associated-fn-called-as-fn.stderr
@@ -0,0 +1,15 @@
+error[E0425]: cannot find function `collect_primary` in this scope
+  --> $DIR/associated-fn-called-as-fn.rs:6:30
+   |
+LL |                 '0'..='9' => collect_primary(&c),
+   |                              ^^^^^^^^^^^^^^^ help: you might have meant to call the associated function: `Self::collect_primary`
+
+error[E0425]: cannot find function `collect_primary` in this scope
+  --> $DIR/associated-fn-called-as-fn.rs:23:30
+   |
+LL |                 '0'..='9' => collect_primary(&c),
+   |                              ^^^^^^^^^^^^^^^ help: you might have meant to call the associated function: `Self::collect_primary`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0425`.
diff --git a/src/test/ui/resolve/issue-14254.stderr b/src/test/ui/resolve/issue-14254.stderr
index 97d42aa8ef4..b1f45adb8b7 100644
--- a/src/test/ui/resolve/issue-14254.stderr
+++ b/src/test/ui/resolve/issue-14254.stderr
@@ -2,7 +2,7 @@ error[E0425]: cannot find function `baz` in this scope
   --> $DIR/issue-14254.rs:19:9
    |
 LL |         baz();
-   |         ^^^ help: try: `self.baz`
+   |         ^^^ help: you might have meant to call the method: `self.baz`
 
 error[E0425]: cannot find value `a` in this scope
   --> $DIR/issue-14254.rs:21:9
@@ -14,7 +14,7 @@ error[E0425]: cannot find function `baz` in this scope
   --> $DIR/issue-14254.rs:28:9
    |
 LL |         baz();
-   |         ^^^ help: try: `self.baz`
+   |         ^^^ help: you might have meant to call the method: `self.baz`
 
 error[E0425]: cannot find value `x` in this scope
   --> $DIR/issue-14254.rs:30:9
@@ -38,7 +38,7 @@ error[E0425]: cannot find value `bah` in this scope
   --> $DIR/issue-14254.rs:36:9
    |
 LL |         bah;
-   |         ^^^ help: try: `Self::bah`
+   |         ^^^ help: you might have meant to call the associated function: `Self::bah`
 
 error[E0425]: cannot find value `b` in this scope
   --> $DIR/issue-14254.rs:38:9
@@ -50,7 +50,7 @@ error[E0425]: cannot find function `baz` in this scope
   --> $DIR/issue-14254.rs:45:9
    |
 LL |         baz();
-   |         ^^^ help: try: `self.baz`
+   |         ^^^ help: you might have meant to call the method: `self.baz`
 
 error[E0425]: cannot find value `x` in this scope
   --> $DIR/issue-14254.rs:47:9
@@ -74,7 +74,7 @@ error[E0425]: cannot find value `bah` in this scope
   --> $DIR/issue-14254.rs:53:9
    |
 LL |         bah;
-   |         ^^^ help: try: `Self::bah`
+   |         ^^^ help: you might have meant to call the associated function: `Self::bah`
 
 error[E0425]: cannot find value `b` in this scope
   --> $DIR/issue-14254.rs:55:9
@@ -86,61 +86,61 @@ error[E0425]: cannot find function `baz` in this scope
   --> $DIR/issue-14254.rs:62:9
    |
 LL |         baz();
-   |         ^^^ help: try: `self.baz`
+   |         ^^^ help: you might have meant to call the method: `self.baz`
 
 error[E0425]: cannot find value `bah` in this scope
   --> $DIR/issue-14254.rs:64:9
    |
 LL |         bah;
-   |         ^^^ help: try: `Self::bah`
+   |         ^^^ help: you might have meant to call the associated function: `Self::bah`
 
 error[E0425]: cannot find function `baz` in this scope
   --> $DIR/issue-14254.rs:71:9
    |
 LL |         baz();
-   |         ^^^ help: try: `self.baz`
+   |         ^^^ help: you might have meant to call the method: `self.baz`
 
 error[E0425]: cannot find value `bah` in this scope
   --> $DIR/issue-14254.rs:73:9
    |
 LL |         bah;
-   |         ^^^ help: try: `Self::bah`
+   |         ^^^ help: you might have meant to call the associated function: `Self::bah`
 
 error[E0425]: cannot find function `baz` in this scope
   --> $DIR/issue-14254.rs:80:9
    |
 LL |         baz();
-   |         ^^^ help: try: `self.baz`
+   |         ^^^ help: you might have meant to call the method: `self.baz`
 
 error[E0425]: cannot find value `bah` in this scope
   --> $DIR/issue-14254.rs:82:9
    |
 LL |         bah;
-   |         ^^^ help: try: `Self::bah`
+   |         ^^^ help: you might have meant to call the associated function: `Self::bah`
 
 error[E0425]: cannot find function `baz` in this scope
   --> $DIR/issue-14254.rs:89:9
    |
 LL |         baz();
-   |         ^^^ help: try: `self.baz`
+   |         ^^^ help: you might have meant to call the method: `self.baz`
 
 error[E0425]: cannot find value `bah` in this scope
   --> $DIR/issue-14254.rs:91:9
    |
 LL |         bah;
-   |         ^^^ help: try: `Self::bah`
+   |         ^^^ help: you might have meant to call the associated function: `Self::bah`
 
 error[E0425]: cannot find function `baz` in this scope
   --> $DIR/issue-14254.rs:98:9
    |
 LL |         baz();
-   |         ^^^ help: try: `self.baz`
+   |         ^^^ help: you might have meant to call the method: `self.baz`
 
 error[E0425]: cannot find value `bah` in this scope
   --> $DIR/issue-14254.rs:100:9
    |
 LL |         bah;
-   |         ^^^ help: try: `Self::bah`
+   |         ^^^ help: you might have meant to call the associated function: `Self::bah`
 
 error: aborting due to 24 previous errors
 
diff --git a/src/test/ui/resolve/issue-2356.stderr b/src/test/ui/resolve/issue-2356.stderr
index 0339daa0d6a..8083233c01b 100644
--- a/src/test/ui/resolve/issue-2356.stderr
+++ b/src/test/ui/resolve/issue-2356.stderr
@@ -8,7 +8,7 @@ error[E0425]: cannot find function `clone` in this scope
   --> $DIR/issue-2356.rs:24:5
    |
 LL |     clone();
-   |     ^^^^^ help: try: `self.clone`
+   |     ^^^^^ help: you might have meant to call the method: `self.clone`
 
 error[E0425]: cannot find function `default` in this scope
   --> $DIR/issue-2356.rs:31:5
@@ -16,7 +16,7 @@ error[E0425]: cannot find function `default` in this scope
 LL |     default();
    |     ^^^^^^^
    |
-help: try
+help: you might have meant to call the associated function
    |
 LL |     Self::default();
    |     ^^^^^^^^^^^^^
@@ -35,7 +35,7 @@ error[E0425]: cannot find function `shave` in this scope
   --> $DIR/issue-2356.rs:41:5
    |
 LL |     shave(4);
-   |     ^^^^^ help: try: `Self::shave`
+   |     ^^^^^ help: you might have meant to call the associated function: `Self::shave`
 
 error[E0425]: cannot find function `purr` in this scope
   --> $DIR/issue-2356.rs:43:5
diff --git a/src/test/ui/resolve/resolve-assoc-suggestions.stderr b/src/test/ui/resolve/resolve-assoc-suggestions.stderr
index a05ac0f8543..b6acaeb8cc2 100644
--- a/src/test/ui/resolve/resolve-assoc-suggestions.stderr
+++ b/src/test/ui/resolve/resolve-assoc-suggestions.stderr
@@ -20,7 +20,7 @@ error[E0412]: cannot find type `Type` in this scope
   --> $DIR/resolve-assoc-suggestions.rs:23:16
    |
 LL |         let _: Type;
-   |                ^^^^ help: try: `Self::Type`
+   |                ^^^^ help: you might have meant to use the associated type: `Self::Type`
 
 error[E0531]: cannot find tuple struct or tuple variant `Type` in this scope
   --> $DIR/resolve-assoc-suggestions.rs:25:13
@@ -50,7 +50,7 @@ error[E0425]: cannot find value `method` in this scope
   --> $DIR/resolve-assoc-suggestions.rs:34:9
    |
 LL |         method;
-   |         ^^^^^^ help: try: `self.method`
+   |         ^^^^^^ help: you might have meant to call the method: `self.method`
 
 error: aborting due to 9 previous errors
 
diff --git a/src/test/ui/resolve/resolve-speculative-adjustment.stderr b/src/test/ui/resolve/resolve-speculative-adjustment.stderr
index 892b50309a9..1c34af6d0ff 100644
--- a/src/test/ui/resolve/resolve-speculative-adjustment.stderr
+++ b/src/test/ui/resolve/resolve-speculative-adjustment.stderr
@@ -20,7 +20,7 @@ error[E0425]: cannot find function `method` in this scope
   --> $DIR/resolve-speculative-adjustment.rs:25:9
    |
 LL |         method();
-   |         ^^^^^^ help: try: `self.method`
+   |         ^^^^^^ help: you might have meant to call the method: `self.method`
 
 error: aborting due to 4 previous errors
 
diff --git a/src/test/ui/suggestions/assoc-type-in-method-return.stderr b/src/test/ui/suggestions/assoc-type-in-method-return.stderr
index bf908d36d2e..202e4a16ead 100644
--- a/src/test/ui/suggestions/assoc-type-in-method-return.stderr
+++ b/src/test/ui/suggestions/assoc-type-in-method-return.stderr
@@ -2,7 +2,7 @@ error[E0412]: cannot find type `Bla` in this scope
   --> $DIR/assoc-type-in-method-return.rs:3:25
    |
 LL |     fn to_bla(&self) -> Bla;
-   |                         ^^^ help: try: `Self::Bla`
+   |                         ^^^ help: you might have meant to use the associated type: `Self::Bla`
 
 error: aborting due to previous error