[TEST] View type borrow expressions

tests/lang/s01_basics/s00_atoms/t04_type_inference_fail_colon_expr.nim

@@ -0,0 +1,16 @@
+discard """
+description: '''
+Type inference does not work if rhs is a complex expression
+'''
+knownIssue: "https://github.com/nim-lang/RFCs/issues/149"
+"""
+
+block infer_set_type:
+    # where this one does work
+    var y: set[char] = {}
+
+    # this one doesn't work (crashes the compiler)
+    var x: set[char] = (discard 12; {})
+
+    # this crashes compiler as well
+    var q: seq[int] = (discard 1; @[])

tests/lang/s06_experimental/readme.md

@@ -0,0 +1 @@
+Directory contains specifications of the features marked as "experimental".

tests/lang/s06_experimental/s01_views/s00_bugs/t01_var_openarray.nim

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+discard """
+description: '''
+`var openarray` must either generate a proper error message or be allowed,
+currently fails with codegen error
+'''
+knownIssue: "var openarray fails with C codegen errro"
+
+"""
+
+{.experimental: "views".}
+
+## feature-documentation
+
+block view_regular_array:
+  var simpleArray = @[0, 1, 2, 3, 4, 5]
+
+  var view: var openarray[int] = toOpenArray(simpleArray, 1, 3)
+
+  doAssert view[0] == 1

tests/lang/s06_experimental/s01_views/s00_bugs/t02_borrow_literal.nim

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+discard """
+description: '''
+C codegen error when trying to borrow from the literal. Should be a
+nim compilation error.
+'''
+knownIssue: "codegen-fail on literal value borrow"
+
+"""
+{.experimental: "views".}
+
+proc block_trivial_borrow() =
+  var view: lent int = 12
+
+block_trivial_borrow()

tests/lang/s06_experimental/s01_views/s01_path_expressions/readme.md

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+This directory contains tests for the path expression inference.
+Each file tests whether original location is sealed correctly and as such
+expects compilation error to occur.

tests/lang/s06_experimental/s01_views/s01_path_expressions/t01_trivial_borrow_fail.nim

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+discard """
+description: '''
+Cannot mutate location of a trivial borrow
+'''
+errormsg: "'view' borrows from location 'source' which does not live long enough"
+"""
+
+{.experimental: "views".}
+
+proc block_trivial_borrow() =
+  ## source itself is a path expression.
+
+  var source = 12
+
+  var view: var int = source
+
+  source = 24
+
+  discard view
+
+block_trivial_borrow()

tests/lang/s06_experimental/s01_views/s01_path_expressions/t02_container_borrow_fail.nim

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+discard """
+description: '''
+Cannot mutate location of a container access
+'''
+errormsg: "cannot borrow view; what it borrows from is potentially mutated"
+"""
+
+{.experimental: "views".}
+
+proc block_container_borrow() =
+  ## Container access like `e[i]` is a path expression.
+
+  var source: seq[int] = @[0, 1, 2]
+
+  let idx0 = 1
+  var view: var int = source[idx0]
+
+  let idx1 = 0
+  source[idx1] = 24
+
+  discard view
+
+block_container_borrow()

tests/lang/s06_experimental/s01_views/s01_path_expressions/t03_tuple_borrow_fail.nim

@@ -0,0 +1,25 @@
+discard """
+description: '''
+Cannot mutate location of a container access
+'''
+errormsg: "cannot borrow view; what it borrows from is potentially mutated"
+line: 18
+"""
+
+{.experimental: "views".}
+
+proc block_tuple_borrow() =
+  ## Tuple access e[0] is a path expression.
+
+  var source: (int, int) = (1, 2)
+
+  var view: var int = source[0]
+
+  ## Location access only tracks single element of a tuple, so it is
+  ## possible to mutate other elements.
+  source[1] = 200
+  source[0] = 24
+
+  discard view
+
+block_tuple_borrow()

tests/lang/s06_experimental/s01_views/s01_path_expressions/t04_field_borrow_fail.nim

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+discard """
+description: '''
+Cannot mutate location of a container access
+'''
+errormsg: "cannot borrow view; what it borrows from is potentially mutated"
+"""
+
+{.experimental: "views".}
+
+type
+  Object = object
+    field1: int
+    field2: int
+
+proc block_trivial_borrow() =
+  ## Object field access e.field is a path expression.
+
+  var source = Object()
+
+  var view: var int = source.field1
+
+  ## Path expression tracks only specific fields, so all other ones can
+  ## be modified as needed.
+  source.field2 = 12
+  source.field1 = 10
+
+  discard view
+
+block_trivial_borrow()

tests/lang/s06_experimental/s01_views/s01_path_expressions/t05_to_openarray_borrow_fail.nim

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+discard """
+description: '''
+Cannot mutate location of an openarray
+'''
+errormsg: "cannot borrow view; what it borrows from is potentially mutated"
+"""
+
+{.experimental: "views".}
+
+proc block_to_openarray_borrow() =
+  ## `system.toOpenArray(e, ...)` is a path expression.
+
+  var source = @[1, 2, 3]
+
+  var view: openarray[int] = toOpenArray(source, 0, 1)
+
+  source[0] = 12
+
+  discard view
+
+block_to_openarray_borrow()

tests/lang/s06_experimental/s01_views/s01_path_expressions/t06_pointer_deref_borrow_fail.nim

@@ -0,0 +1,22 @@
+discard """
+description: '''
+Cannot mutate location created from pointer dereference
+'''
+errormsg: "'view' borrows from location 'source' which does not live long enough"
+"""
+
+{.experimental: "views".}
+
+proc block_pointer_deref_borrow() =
+  ## Pointer dereference `e[]` is a path expression.
+
+  var data = 12
+  var source = addr data
+
+  var view: lent int = source[]
+
+  source = addr data
+
+  discard view
+
+block_pointer_deref_borrow()

tests/lang/s06_experimental/s01_views/s01_path_expressions/t07_addr_borrow_fail.nim

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+discard """
+description: '''
+addr is not detected as a path expresesion
+'''
+knownIssue: "addr is not a path expression"
+
+"""
+
+
+{.experimental: "views".}
+
+proc block_pointer_deref_borrow() =
+  ## An address `addr e`, is a path expression.
+
+  var source = 12
+
+  var view: ptr lent int = addr source
+
+  source = 12
+
+  discard view
+
+block_pointer_deref_borrow()

tests/lang/s06_experimental/s01_views/s01_path_expressions/t08_type_conversion_borrow_fail.nim

@@ -0,0 +1,23 @@
+discard """
+description: '''
+Cannot mutate location of a container access
+'''
+errormsg: "'view' borrows from location 'source' which does not live long enough"
+"""
+
+{.experimental: "views".}
+
+proc block_type_conversion_borrow() =
+  ## Object field access e.field is a path expression.
+
+  var source = int16(12)
+
+  var view: var int = int32(source)
+
+  ## Path expression tracks only specific fields, so all other ones can
+  ## be modified as needed.
+  source = 10
+
+  discard view
+
+block_type_conversion_borrow()

tests/lang/s06_experimental/s01_views/s01_path_expressions/t09_proc_param_borrow_fail.nim

@@ -0,0 +1,26 @@
+discard """
+description: '''
+Cannot mutate borrow of the first argument
+'''
+errormsg: "cannot borrow view; what it borrows from is potentially mutated"
+"""
+
+{.experimental: "views".}
+
+proc borrowArg(e: var int): lent int = e
+
+proc block_argument_borrow() =
+  ## source itself is a path expression.
+
+  block borrow_arg_call:
+    ## example-explanation
+
+    var source = 12
+
+    var view: var int = borrowArg(source)
+
+    source = 24
+
+    discard view
+
+block_argument_borrow()

tests/lang/s06_experimental/s01_views/s02_array_views.nim

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+discard """
+description: '''
+Creating and accessing views for the array types
+'''
+
+"""
+
+{.experimental: "views".}
+
+## feature-documentation
+
+proc `sealedBorrow`() =
+  var simpleArray = [0, 1, 2, 3, 4, 5]
+
+  var view: openarray[int] = toOpenArray(simpleArray, 1, 3)
+
+  ## Openarray can only access a section of the original data, so indexing
+  ## miggh be offset.
+  doAssert view[0] == 1
+
+  ## Underlying elements might be modified
+  simpleArray[1] = 12
+
+  ## And as a result, view into this section is also affected.
+  doAssert view[0] == 12
+
+  view[2] = 24
+
+  doAssert simpleArray[3] == 24
+
+`sealedBorrow`()
+
+

tests/lang/s06_experimental/s01_views/t01_array_fail_sealed_borrow.nim

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+discard """
+description: '''
+Cannot mutate sealed location
+'''
+errormsg: "cannot borrow view; what it borrows from is potentially mutated"
+
+
+"""
+
+{.experimental: "views".}
+
+proc `sealedBorrow`() =
+  var simpleArray = [0, 1, 2, 3, 4, 5]
+
+  var view: openarray[int] = toOpenArray(simpleArray, 1, 3)
+
+  ## Openarray can only access a section of the original data, so indexing
+  ## miggh be offset.
+  doAssert view[0] == 1
+
+  ## Because `view` is accessed later, it is not possible to mutate original data
+  ## as it would result the change in the borrowed view.
+  simpleArray[1] = 12
+
+  doAssert view[0] == 12
+
+
+`sealedBorrow`()