Rollup merge of #100750 - akabinds:akabinds/improved-invalid-function-qual-error, r=davidtwco

improved diagnostic for function defined with `def`, `fun`, `func`, or `function` instead of `fn`

Closes #99751

src/test/ui/parser/fn-defined-using-def.rs

@@ -0,0 +1,10 @@
+// Check what happens when `def` is used to define a function, instead of `fn`
+// edition:2021
+
+#![allow(dead_code)]
+
+def foo() {}
+//~^ ERROR expected one of `!` or `::`, found `foo`
+//~^^ HELP write `fn` instead of `def` to declare a function
+
+fn main() {}

src/test/ui/parser/fn-defined-using-def.stderr

@@ -0,0 +1,10 @@
+error: expected one of `!` or `::`, found `foo`
+  --> $DIR/fn-defined-using-def.rs:6:5
+   |
+LL | def foo() {}
+   | --- ^^^ expected one of `!` or `::`
+   | |
+   | help: write `fn` instead of `def` to declare a function
+
+error: aborting due to previous error
+

src/test/ui/parser/fn-defined-using-fun.rs

@@ -0,0 +1,10 @@
+// Check what happens when `fun` is used to define a function, instead of `fn`
+// edition:2021
+
+#![allow(dead_code)]
+
+fun foo() {}
+//~^ ERROR expected one of `!` or `::`, found `foo`
+//~^^ HELP write `fn` instead of `fun` to declare a function
+
+fn main() {}

src/test/ui/parser/fn-defined-using-fun.stderr

@@ -0,0 +1,10 @@
+error: expected one of `!` or `::`, found `foo`
+  --> $DIR/fn-defined-using-fun.rs:6:5
+   |
+LL | fun foo() {}
+   | --- ^^^ expected one of `!` or `::`
+   | |
+   | help: write `fn` instead of `fun` to declare a function
+
+error: aborting due to previous error
+

src/test/ui/parser/fn-defined-using-func.rs

@@ -0,0 +1,10 @@
+// Check what happens when `func` is used to define a function, instead of `fn`
+// edition:2021
+
+#![allow(dead_code)]
+
+func foo() {}
+//~^ ERROR expected one of `!` or `::`, found `foo`
+//~^^ HELP write `fn` instead of `func` to declare a function
+
+fn main() {}

src/test/ui/parser/fn-defined-using-func.stderr

@@ -0,0 +1,10 @@
+error: expected one of `!` or `::`, found `foo`
+  --> $DIR/fn-defined-using-func.rs:6:6
+   |
+LL | func foo() {}
+   | ---- ^^^ expected one of `!` or `::`
+   | |
+   | help: write `fn` instead of `func` to declare a function
+
+error: aborting due to previous error
+

src/test/ui/parser/fn-defined-using-function.rs

@@ -0,0 +1,10 @@
+// Check what happens when `function` is used to define a function, instead of `fn`
+// edition:2021
+
+#![allow(dead_code)]
+
+function foo() {}
+//~^ ERROR expected one of `!` or `::`, found `foo`
+//~^^ HELP write `fn` instead of `function` to declare a function
+
+fn main() {}

src/test/ui/parser/fn-defined-using-function.stderr

@@ -0,0 +1,10 @@
+error: expected one of `!` or `::`, found `foo`
+  --> $DIR/fn-defined-using-function.rs:6:10
+   |
+LL | function foo() {}
+   | -------- ^^^ expected one of `!` or `::`
+   | |
+   | help: write `fn` instead of `function` to declare a function
+
+error: aborting due to previous error
+