Put a space before colon that appears after a meta variable

Closes #2534.

Author: topecongiro

src/macros.rs

@@ -522,6 +522,7 @@ impl MacroArgKind {
             _ => false,
         }
     }
+
     fn starts_with_dollar(&self) -> bool {
         match *self {
             MacroArgKind::Repeat(..) | MacroArgKind::MetaVariable(..) => true,
@@ -777,6 +778,9 @@ impl MacroArgParser {
             if ident_like(&self.start_tok) {
                 return true;
             }
+            if self.start_tok == Token::Colon {
+                return true;
+            }
         }
 
         if force_space_before(&self.start_tok) {

tests/source/macro_rules.rs

@@ -147,6 +147,12 @@ macro foo($type_name: ident, $docs: expr) {
     pub struct $type_name;
 }
 
+// #2534
+macro_rules! foo {
+    ($a:ident : $b:ty) => {};
+    ($a:ident $b:ident $c:ident) => {};
+}
+
 // #2538
 macro_rules! add_message_to_notes {
     ($msg:expr) => {{

tests/target/macro_rules.rs

@@ -15,8 +15,8 @@ macro_rules! m {
     ) => {};
     ($name: ident($($dol: tt $var: ident)*) $($body: tt)*) => {};
     (
-        $($i: ident: $ty: ty, $def: expr, $stb: expr, $($dstring: tt),+);+ $(;)*
-        $($i: ident: $ty: ty, $def: expr, $stb: expr, $($dstring: tt),+);+ $(;)*
+        $($i: ident : $ty: ty, $def: expr, $stb: expr, $($dstring: tt),+);+ $(;)*
+        $($i: ident : $ty: ty, $def: expr, $stb: expr, $($dstring: tt),+);+ $(;)*
     ) => {};
     ($foo: tt foo[$attr: meta] $name: ident) => {};
     ($foo: tt[$attr: meta] $name: ident) => {};
@@ -28,7 +28,7 @@ macro_rules! m {
 }
 
 macro_rules! impl_a_method {
-    ($n: ident($a: ident: $ta: ty) -> $ret: ty { $body: expr }) => {
+    ($n: ident($a: ident : $ta: ty) -> $ret: ty { $body: expr }) => {
         fn $n($a: $ta) -> $ret {
             $body
         }
@@ -38,7 +38,7 @@ macro_rules! impl_a_method {
             };
         }
     };
-    ($n: ident($a: ident: $ta: ty, $b: ident: $tb: ty) -> $ret: ty { $body: expr }) => {
+    ($n: ident($a: ident : $ta: ty, $b: ident : $tb: ty) -> $ret: ty { $body: expr }) => {
         fn $n($a: $ta, $b: $tb) -> $ret {
             $body
         }
@@ -49,7 +49,7 @@ macro_rules! impl_a_method {
         }
     };
     (
-        $n: ident($a: ident: $ta: ty, $b: ident: $tb: ty, $c: ident: $tc: ty) ->
+        $n: ident($a: ident : $ta: ty, $b: ident : $tb: ty, $c: ident : $tc: ty) ->
         $ret: ty { $body: expr }
     ) => {
         fn $n($a: $ta, $b: $tb, $c: $tc) -> $ret {
@@ -62,7 +62,7 @@ macro_rules! impl_a_method {
         }
     };
     (
-        $n: ident($a: ident: $ta: ty, $b: ident: $tb: ty, $c: ident: $tc: ty, $d: ident: $td: ty) ->
+        $n: ident($a: ident : $ta: ty, $b: ident : $tb: ty, $c: ident : $tc: ty, $d: ident : $td: ty) ->
         $ret: ty { $body: expr }
     ) => {
         fn $n($a: $ta, $b: $tb, $c: $tc, $d: $td) -> $ret {
@@ -180,6 +180,12 @@ macro foo($type_name: ident, $docs: expr) {
     pub struct $type_name;
 }
 
+// #2534
+macro_rules! foo {
+    ($a: ident : $b: ty) => {};
+    ($a: ident $b: ident $c: ident) => {};
+}
+
 // #2538
 macro_rules! add_message_to_notes {
     ($msg: expr) => {{