Support begin/end indexing of SourceFile (#201)

Author: timholy

src/source_files.jl

@@ -109,6 +109,9 @@ function Base.getindex(source::SourceFile, i::Int)
     source.code[i]
 end
 
+Base.firstindex(source::SourceFile) = firstindex(source.code)
+Base.lastindex(source::SourceFile) = lastindex(source.code)
+
 """
     sourcetext(source::SourceFile)
 

test/source_files.jl

@@ -26,4 +26,14 @@
         @test source_location(SourceFile(; filename=path), 1) == (1,1)
         @test source_location(SourceFile(; filename=path, first_line=7), 1) == (7,1)
     end
+
+    @test SourceFile("a\nb\n")[1:2] == "a\n"
+    @test SourceFile("a\nb\n")[3:end] == "b\n"
+    if Base.VERSION >= v"1.4"
+        # Protect the `[begin` from being viewed by the parser on older Julia versions
+        @test eval(Meta.parse("""SourceFile("a\nb\n")[begin:end]""")) == "a\nb\n"
+    end
+
+    # unicode
+    @test SourceFile("αβ")[1:2] == "α"
 end