Fix a pretty-printing case.

There are a few cases where there should be a space between an
identifier and a `(`, when the identifier is a keyword like `let` or
`if` or `while`.

Author: nnethercote

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -175,11 +175,17 @@ fn space_between(tt1: &TokenTree, tt2: &TokenTree) -> bool {
         // ANYTHING + `.`: `x.y`, `tup.0`
         (_, Tok(Token { kind: Comma | Semi | Dot, .. }, _)) => false,
 
-        // IDENT + `(`: `f(3)`
-        //
-        // FIXME: Incorrect cases:
-        // - Let: `let(a, b) = (1, 2)`
-        (Tok(Token { kind: Ident(..), .. }, _), Del(_, Parenthesis, _)) => false,
+        // IDENT|`fn`|`Self`|`pub` + `(`: `f(3)`, `fn(x: u8)`, `Self()`, `pub(crate)`,
+        // but `let (a, b) = (1, 2)` needs a space after the `let`
+        (Tok(Token { kind: Ident(sym, is_raw), span }, _), Del(_, Parenthesis, _))
+            if !Ident::new(*sym, *span).is_reserved()
+                || *sym == kw::Fn
+                || *sym == kw::SelfUpper
+                || *sym == kw::Pub
+                || *is_raw =>
+        {
+            false
+        }
 
         // `#` + `[`: `#[attr]`
         (Tok(Token { kind: Pound, .. }, _), Del(_, Bracket, _)) => false,

tests/ui/macros/stringify.rs

@@ -655,11 +655,11 @@ fn test_stmt() {
     c2!(stmt, [ let _ ], "let _;", "let _");
     c2!(stmt, [ let x = true ], "let x = true;", "let x = true");
     c2!(stmt, [ let x: bool = true ], "let x: bool = true;", "let x : bool = true");
-    c2!(stmt, [ let (a, b) = (1, 2) ], "let (a, b) = (1, 2);", "let(a, b) = (1, 2)"); // FIXME
+    c2!(stmt, [ let (a, b) = (1, 2) ], "let (a, b) = (1, 2);", "let (a, b) = (1, 2)");
     c2!(stmt,
         [ let (a, b): (u32, u32) = (1, 2) ],
         "let (a, b): (u32, u32) = (1, 2);",
-        "let(a, b) : (u32, u32) = (1, 2)"
+        "let (a, b) : (u32, u32) = (1, 2)"
     );
 
     // StmtKind::Item

tests/ui/proc-macro/issue-76182-leading-vert-pat.stdout

@@ -1,4 +1,4 @@
-PRINT-ATTR INPUT (DISPLAY): fn main() { match() { | () => () } }
+PRINT-ATTR INPUT (DISPLAY): fn main() { match () { | () => () } }
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Ident {
         ident: "fn",