Don't compute indents when in a string

compiler/src/dotty/tools/dotc/parsing/Scanners.scala

@@ -265,7 +265,7 @@ object Scanners {
     val next = newTokenData
     private val prev = newTokenData
 
-    /** The current region. This is initially an Indented region with indentation width. */
+    /** The current region. This is initially an Indented region with zero indentation width. */
     var currentRegion: Region = Indented(IndentWidth.Zero, Set(), EMPTY, null)
 
 // Get next token ------------------------------------------------------------
@@ -434,8 +434,8 @@ object Scanners {
       && !migrateTo3
       && !noindentSyntax
 
-    /** The indentation width of the given offset */
-    def indentWidth(offset: Offset): IndentWidth = {
+    /** The indentation width of the given offset. */
+    def indentWidth(offset: Offset): IndentWidth =
       import IndentWidth.{Run, Conc}
       def recur(idx: Int, ch: Char, n: Int, k: IndentWidth => IndentWidth): IndentWidth =
         if (idx < 0) k(Run(ch, n))
@@ -452,7 +452,7 @@ object Scanners {
           else recur(idx - 1, ' ', 0, identity)
         }
       recur(offset - 1, ' ', 0, identity)
-    }
+    end indentWidth
 
     /** Handle newlines, possibly inserting an INDENT, OUTDENT, NEWLINE, or NEWLINES token
      *  in front of the current token. This depends on whether indentation is significant or not.
@@ -521,6 +521,7 @@ object Scanners {
           lastWidth = r.width
           newlineIsSeparating = lastWidth <= nextWidth || r.isOutermost
           indentPrefix = r.prefix
+        case _: InString => ()
         case r =>
           indentIsSignificant = indentSyntax
           r.proposeKnownWidth(nextWidth, lastToken)
@@ -1424,7 +1425,7 @@ object Scanners {
     nextToken()
     currentRegion = topLevelRegion(indentWidth(offset))
   }
-  // end Scanner
+  end Scanner
 
   /** A Region indicates what encloses the current token. It can be one of the following
    *

tests/neg/i14386.scala

@@ -0,0 +1,48 @@
+// scalac: -Werror
+def logLevelDetail(level: Int): String =
+   s"""$level
+
+// the following line is indented using [tab][tab]
+		Sets the global logging level to $level.
+    """
+ /* was 2 errors with carets as shown
+  |                                               ^    ^
+  |                                               Incompatible combinations of tabs and spaces in indentation prefixes.
+  |                                               Previous indent : 3 spaces
+  |                                               Latest indent   : 2 tabs
+  */
+
+def log(level: Int, msg: String): String =
+  s"""
+		$level
+  prefixed $level suffixed
+  """
+/*
+            ^    ^
+            Incompatible combinations of tabs and spaces in indentation prefixes.
+            Previous indent : 2 tabs
+            Latest indent   : 2 space
+ */
+
+// normal mixed tabs errors as a baseline
+def g =
+    42
+	+ 17   // error
+
+def p() =
+    println("hello")
+	println("world")  // error
+  /*
+   |    Incompatible combinations of tabs and spaces in indentation prefixes.
+   |    Previous indent : 4 spaces
+   |    Latest indent   : 1 tab
+   */
+
+def braced() =
+  s"""begin
+  ${
+      val level = 10
+    val msg = "hello, world"  // error he lets me off with a warning
+    log(level, msg)           // error
+   }
+   end"""