Fix column method.

In case if code is indented with tabs `column` was always retuning `0`.

Originally reported in scalamete/metals#3724

Author: dos65

compiler/src/dotty/tools/dotc/util/SourceFile.scala

@@ -75,9 +75,6 @@ class SourceFile(val file: AbstractFile, computeContent: => Array[Char]) extends
 
   def maybeIncomplete: Boolean = _maybeInComplete
 
-  /** Tab increment; can be overridden */
-  def tabInc: Int = 8
-
   override def name: String = file.name
   override def path: String = file.path
   override def jfile: Optional[JFile] = Optional.ofNullable(file.file)
@@ -197,12 +194,7 @@ class SourceFile(val file: AbstractFile, computeContent: => Array[Char]) extends
   /** The column corresponding to `offset`, starting at 0 */
   def column(offset: Int): Int = {
     var idx = startOfLine(offset)
-    var col = 0
-    while (idx != offset) {
-      col += (if (idx < content().length && content()(idx) == '\t') (tabInc - col) % tabInc else 1)
-      idx += 1
-    }
-    col
+    offset - idx
   }
 
   /** The padding of the column corresponding to `offset`, includes tabs */

tests/semanticdb/expect/Tabs.expect.scala

@@ -0,0 +1,5 @@
+package example
+
+val a/*<-example::Tabs$package.a.*/ =
+	List/*->scala::package.List.*/(1,2,3)
+		.map/*->scala::collection::immutable::List#map().*/(_ +/*->scala::Int#`+`(+4).*/ 1)

tests/semanticdb/expect/Tabs.scala

@@ -0,0 +1,5 @@
+package example
+
+val a = 
+	List(1,2,3)
+		.map(_ + 1)

tests/semanticdb/metac.expect

@@ -3393,6 +3393,34 @@ Synthetics:
 [55:6..55:12):foo(x) => *(x)
 [58:6..58:12):foo(0) => *(given_Int)
 
+expect/Tabs.scala
+-----------------
+
+Summary:
+Schema => SemanticDB v4
+Uri => Tabs.scala
+Text => empty
+Language => Scala
+Symbols => 2 entries
+Occurrences => 5 entries
+Synthetics => 2 entries
+
+Symbols:
+example/Tabs$package. => final package object example extends Object { self: example.type => +2 decls }
+example/Tabs$package.a. => val method a List[Int]
+
+Occurrences:
+[0:8..0:15): example <- example/
+[2:4..2:5): a <- example/Tabs$package.a.
+[3:1..3:5): List -> scala/package.List.
+[4:3..4:6): map -> scala/collection/immutable/List#map().
+[4:9..4:10): + -> scala/Int#`+`(+4).
+
+Synthetics:
+[3:1..4:6):List(1,2,3)
+		.map => *[Int]
+[3:1..3:5):List => *.apply[Int]
+
 expect/Traits.scala
 -------------------