Implement string block literals.

compiler/lexer.nim

@@ -814,6 +814,59 @@ proc getString(L: var Lexer, tok: var Token, mode: StringMode) =
       else:
         tok.literal.add(L.buf[pos])
         inc(pos)
+  elif L.buf[pos] == ':' and L.buf[pos + 1] in {CR, LF}:
+    # string block literal
+    L.bufpos = pos + 1
+    tok.tokType = if mode == normal: tkStrLit
+      else: tkRStrLit
+    let indent = L.currLineIndent + 2
+    while true:
+      # skip indent and/or empty lines without moving lexer
+      var needIndent = indent
+      var emptyLines = -1  # account for previous LF still in buffer
+      var pos = L.bufpos
+      while needIndent > 0:
+        var c = L.buf[pos]
+        if c in {' ', CR, LF}:
+          if c == ' ':
+            dec(needIndent)
+          if c == LF:
+            inc(emptyLines)
+            needIndent = indent
+          inc(pos)
+        else:
+          # end of block found -> cancel lookahead
+          pos = L.bufpos
+          if c != ')': emptyLines = 0
+          break
+      if emptyLines > 0:
+        add(tok.literal, '\n'.repeat(emptyLines))
+      # fast-forward lexer to current position
+      while L.bufpos < pos:
+        if L.buf[L.bufpos] in {CR, LF}:
+          L.bufpos = handleCRLF(L, L.bufpos)
+        else:
+          inc(L.bufpos)
+      # EXIT if end of block was reached
+      if needIndent > 0: break
+      # parse a line of string, break before EOL
+      while true:
+        var c = L.buf[L.bufpos]
+        if c in {CR, LF, nimlexbase.EndOfFile}:
+          add(tok.literal, "\n")
+          break
+        if (c == '\\') and mode == normal:
+          if L.buf[L.bufpos + 1] in {CR, LF, nimlexbase.EndOfFile}:
+            inc(L.bufpos)
+            break
+          else:
+            getEscapedChar(L, tok)
+        else:
+          add(tok.literal, c)
+          inc(L.bufpos)
+    if tok.literal == "":
+      lexMessage(L, errGenerated, "string block literal indented by two spaces expected")
+      tokenEndIgnore(tok, L.bufpos)
   else:
     # ordinary string literal
     if mode != normal: tok.tokType = tkRStrLit