Addressed issues mentioned in the code review

Author: slavaschmidt

readme/Configuration.scalatex

@@ -771,6 +771,20 @@
         while(a) foo()
         for(a <- as) foo()
 
+    @sect{spaces.afterSymbolicDefs}
+      Default: @b(default.spaces.afterSymbolicDefs)
+
+      @hl.scala
+        // spaces.afterSymbolicDefs = true
+        trait Test[A] {
+          def <=> [B](that: Test[B]): Int
+        }
+
+        // spaces.afterSymbolicDefs = false
+        trait Test[A] {
+          def <=>[B](that: Test[B]): Int
+        }
+
     @sect{includeCurlyBraceInSelectChains}
       Default: @b(default.includeCurlyBraceInSelectChains)
 

scalafmt-core/shared/src/main/scala/org/scalafmt/config/Spaces.scala

@@ -21,6 +21,9 @@ import org.scalafmt.config.SpaceBeforeContextBound.Never
   * @param inByNameTypes
   *   If false, removes space in by-name parameter.
   *   `def foo(a: =>A)`
+  * @param afterSymbolicDefs If true, adds a single space after an operator method
+  *   For example:
+  *   def <=> [T](that: T): Boolean
   */
 case class Spaces(
     beforeContextBoundColon: SpaceBeforeContextBound = Never,
@@ -29,7 +32,8 @@ case class Spaces(
     inParentheses: Boolean = false,
     neverAroundInfixTypes: Seq[String] = Nil,
     afterKeywordBeforeParen: Boolean = true,
-    inByNameTypes: Boolean = true
+    inByNameTypes: Boolean = true,
+    afterSymbolicDefs: Boolean = true
 ) {
   implicit val reader: ConfDecoder[Spaces] = generic.deriveDecoder(this).noTypos
 }

scalafmt-core/shared/src/main/scala/org/scalafmt/internal/Router.scala

@@ -37,7 +37,6 @@ import org.scalafmt.util.TokenOps
 import org.scalafmt.util.TreeOps
 import org.scalafmt.util.Trivia
 
-import scala.meta.Decl.Def
 import scala.meta.Lit
 
 // Too many to import individually.
@@ -75,7 +74,6 @@ class Router(formatOps: FormatOps) {
     val leftOwner = owners(formatToken.left)
     val rightOwner = owners(formatToken.right)
     val newlines = newlinesBetween(formatToken.between)
-    val isDef = rightOwner.tokens.headOption.exists(_.is[KwDef])
 
     formatToken match {
       case FormatToken(_: BOF, _, _) =>
@@ -359,10 +357,10 @@ class Router(formatOps: FormatOps) {
       // Opening [ with no leading space.
       // Opening ( with no leading space.
       case FormatToken(
-          KwSuper() | KwThis() | Ident(_) | RightBracket() | RightBrace() |
-          RightParen() | Underscore(),
-          LeftParen() | LeftBracket(),
-          _) if noSpaceBeforeOpeningParen(rightOwner) && {
+            KwSuper() | KwThis() | Ident(_) | RightBracket() | RightBrace() |
+            RightParen() | Underscore(),
+            LeftParen() | LeftBracket(),
+            _) if noSpaceBeforeOpeningParen(rightOwner) && {
             leftOwner.parent.forall {
               // infix applications have no space.
               case _: Type.ApplyInfix | _: Term.ApplyInfix => false
@@ -375,7 +373,8 @@ class Router(formatOps: FormatOps) {
               if style.spaces.afterTripleEquals &&
                 t.tokens.map(_.syntax) == Seq("===") =>
             Space
-          case name: Term.Name if isDef && isSymbolicName(name.value) =>
+          case name: Term.Name
+              if isSymbolicName(name.value) && name.parent.exists(isDefDef) =>
             Space
           case _ => NoSplit
         }

scalafmt-tests/src/test/resources/unit/UnaryApply.stat

@@ -27,7 +27,8 @@
 <<< #697 you shall not change AST!!
   def =!=(that: S): Boolean = ! ===(that)
 >>>
-def =!=(that: S): Boolean = ! ===(that)
+def =!= (that: S): Boolean =
+  ! ===(that)
 <<< #710 you shall not add unneeded space!!
   if (!_member) Some(x) else None
 >>>