Suggest more uses of >= over =>

Author: sjwang05

compiler/rustc_parse/src/parser/diagnostics.rs

@@ -610,6 +610,16 @@ impl<'a> Parser<'a> {
         // FIXME: translation requires list formatting (for `expect`)
         let mut err = self.struct_span_err(self.token.span, msg_exp);
 
+        // Look for usages of '=>' where '>=' was probably intended
+        if self.token == token::FatArrow {
+            err.span_suggestion(
+                self.token.span,
+                "you probably meant to write a \"greater than or equal to\" comparison",
+                ">=",
+                Applicability::Unspecified,
+            );
+        }
+
         if let TokenKind::Ident(symbol, _) = &self.prev_token.kind {
             if ["def", "fun", "func", "function"].contains(&symbol.as_str()) {
                 err.span_suggestion_short(

compiler/rustc_parse/src/parser/expr.rs

@@ -2435,7 +2435,7 @@ impl<'a> Parser<'a> {
                     self.error_on_extra_if(&cond)?;
                     // Parse block, which will always fail, but we can add a nice note to the error
                     self.parse_block().map_err(|mut err| {
-                        // Look for usages of '=>' where '>=' was probably intended.
+                        // Look for usages of '=>' where '>=' was probably intended
                         if maybe_fatarrow.kind == token::FatArrow {
                             err.span_suggestion(
                                 maybe_fatarrow.span,

tests/ui/parser/eq-gt-to-gt-eq.rs

@@ -2,37 +2,42 @@
 
 fn main() {
     let a = 0;
-    let b = 4;
-    if a => b { //~ERROR
-        println!("yay!");
-    }
+    let b = 1;
+    if a => b {} //~ERROR
 }
 
 fn foo() {
     let a = 0;
-    if a => 4 { //~ERROR
-        println!("yay!");
-    }
+    if a => 1 {} //~ERROR
+}
+
+fn a() {
+    let a = 0;
+    if 1 => a {} //~ERROR
 }
 
 fn bar() {
     let a = 0;
-    let b = 4;
-    if a => b && true { //~ERROR
-        println!("yay!");
-    }
+    let b = 1;
+    if a => b && a != b {} //~ERROR
 }
 
 fn qux() {
     let a = 0;
-    let b = 4;
-    if true && a => b { //~ERROR
-        println!("yay!");
-    }
+    let b = 1;
+    if a != b && a => b {} //~ERROR
 }
 
 fn baz() {
     let a = 0;
-    let b = 4;
+    let b = 1;
     let _ = a => b; //~ERROR
 }
+
+fn b() {
+    let a = 0;
+    let b = 1;
+    match a => b { //~ERROR
+        _ => todo!(),
+    }
+}

tests/ui/parser/eq-gt-to-gt-eq.stderr

@@ -1,25 +1,81 @@
 error: expected `{`, found `=>`
   --> $DIR/eq-gt-to-gt-eq.rs:6:10
    |
-LL |     if a => b {
+LL |     if a => b {}
    |          ^^ expected `{`
    |
 help: you probably meant to write a "greater than or equal to" comparison
    |
-LL |     if a >= b {
+LL |     if a >= b {}
    |          ~~
 
-error: expected expression, found `>`
-  --> $DIR/eq-gt-to-gt-eq.rs:14:12
+error: expected `{`, found `=>`
+  --> $DIR/eq-gt-to-gt-eq.rs:11:10
+   |
+LL |     if a => 1 {}
+   |          ^^ expected `{`
+   |
+help: you probably meant to write a "greater than or equal to" comparison
+   |
+LL |     if a >= 1 {}
+   |          ~~
+
+error: expected `{`, found `=>`
+  --> $DIR/eq-gt-to-gt-eq.rs:16:10
+   |
+LL |     if 1 => a {}
+   |          ^^ expected `{`
+   |
+help: you probably meant to write a "greater than or equal to" comparison
+   |
+LL |     if 1 >= a {}
+   |          ~~
+
+error: expected `{`, found `=>`
+  --> $DIR/eq-gt-to-gt-eq.rs:22:10
+   |
+LL |     if a => b && a != b {}
+   |          ^^ expected `{`
+   |
+help: you probably meant to write a "greater than or equal to" comparison
+   |
+LL |     if a >= b && a != b {}
+   |          ~~
+
+error: expected `{`, found `=>`
+  --> $DIR/eq-gt-to-gt-eq.rs:28:20
+   |
+LL |     if a != b && a => b {}
+   |                    ^^ expected `{`
+   |
+help: you probably meant to write a "greater than or equal to" comparison
    |
-LL |     if a = >b {
-   |            ^ expected expression
+LL |     if a != b && a >= b {}
+   |                    ~~
 
-error: expected expression, found `>`
-  --> $DIR/eq-gt-to-gt-eq.rs:22:12
+error: expected one of `!`, `.`, `::`, `;`, `?`, `else`, `{`, or an operator, found `=>`
+  --> $DIR/eq-gt-to-gt-eq.rs:34:15
+   |
+LL |     let _ = a => b;
+   |               ^^ expected one of 8 possible tokens
+   |
+help: you probably meant to write a "greater than or equal to" comparison
+   |
+LL |     let _ = a >= b;
+   |               ~~
+
+error: expected one of `!`, `.`, `::`, `?`, `{`, or an operator, found `=>`
+  --> $DIR/eq-gt-to-gt-eq.rs:40:13
+   |
+LL |     match a => b {
+   |     -----   ^^ expected one of `!`, `.`, `::`, `?`, `{`, or an operator
+   |     |
+   |     while parsing this `match` expression
+   |
+help: you probably meant to write a "greater than or equal to" comparison
    |
-LL |     if a = > b {
-   |            ^ expected expression
+LL |     match a >= b {
+   |             ~~
 
-error: aborting due to 3 previous errors
+error: aborting due to 7 previous errors