Support splats on left-hand sides of multiple assignment expressions (#…

…10410)

spec/compiler/codegen/multi_assign_spec.cr

@@ -0,0 +1,191 @@
+require "../../spec_helper"
+
+describe "Code gen: multi assign" do
+  it "supports n to n assignment" do
+    run(<<-CR).to_i.should eq(123)
+      a, b, c = 1, 2, 3
+      a &* 100 &+ b &* 10 &+ c
+      CR
+  end
+
+  it "supports 1 to n assignment" do
+    run(<<-CR).to_i.should eq(123)
+      class Foo
+        def [](index)
+          index &+ 1
+        end
+      end
+
+      a, b, c = Foo.new
+      a &* 100 &+ b &* 10 &+ c
+      CR
+  end
+
+  it "supports m to n assignment, with splat on left-hand side (1)" do
+    run(<<-CR).to_i.should eq(12345)
+      #{tuple_new}
+
+      a, *b, c = 1, 2, 3, 4, 5
+      a &* 10000 &+ b[0] &* 1000 &+ b[1] &* 100 &+ b[2] &* 10 &+ c
+      CR
+  end
+
+  it "supports m to n assignment, with splat on left-hand side (2)" do
+    run(<<-CR).to_i.should eq(12345)
+      #{tuple_new}
+
+      *a, b, c = 1, 2, 3, 4, 5
+      a[0] &* 10000 &+ a[1] &* 1000 &+ a[2] &* 100 &+ b &* 10 &+ c
+      CR
+  end
+
+  it "supports m to n assignment, with splat on left-hand side (3)" do
+    run(<<-CR).to_i.should eq(12345)
+      #{tuple_new}
+
+      a, b, *c = 1, 2, 3, 4, 5
+      a &* 10000 &+ b &* 1000 &+ c[0] &* 100 &+ c[1] &* 10 &+ c[2]
+      CR
+  end
+
+  it "supports m to n assignment, splat is empty tuple (1)" do
+    run(<<-CR).to_b.should be_true
+      #{tuple_new}
+
+      _, *x, _ = 1, 2
+      x.is_a?(Tuple(*typeof(Tuple.new)))
+      CR
+  end
+
+  it "supports m to n assignment, splat is empty tuple (2)" do
+    run(<<-CR).to_b.should be_true
+      #{tuple_new}
+
+      *x, _, _ = 1, 2
+      x.is_a?(Tuple(*typeof(Tuple.new)))
+      CR
+  end
+
+  it "supports m to n assignment, splat is empty tuple (3)" do
+    run(<<-CR).to_b.should be_true
+      #{tuple_new}
+
+      _, _, *x = 1, 2
+      x.is_a?(Tuple(*typeof(Tuple.new)))
+      CR
+  end
+
+  it "supports 1 to n assignment, with splat on left-hand side (1)" do
+    run(<<-CR).to_i.should eq(12345)
+      require "prelude"
+
+      a, *b, c = {1, 2, 3, 4, 5}
+      a &* 10000 &+ b[0] &* 1000 &+ b[1] &* 100 &+ b[2] &* 10 &+ c
+      CR
+  end
+
+  it "supports 1 to n assignment, with splat on left-hand side (2)" do
+    run(<<-CR).to_i.should eq(12345)
+      #{range_new}
+
+      *a, b, c = {1, 2, 3, 4, 5}
+      a[0] &* 10000 &+ a[1] &* 1000 &+ a[2] &* 100 &+ b &* 10 &+ c
+      CR
+  end
+
+  it "supports 1 to n assignment, with splat on left-hand side (3)" do
+    run(<<-CR).to_i.should eq(12345)
+      #{range_new}
+
+      a, b, *c = {1, 2, 3, 4, 5}
+      a &* 10000 &+ b &* 1000 &+ c[0] &* 100 &+ c[1] &* 10 &+ c[2]
+      CR
+  end
+
+  it "supports 1 to n assignment, splat is empty (1)" do
+    run(<<-CR).to_b.should be_true
+      require "prelude"
+
+      _, *x, _ = {1, 2}
+      x.is_a?(Tuple(*typeof(Tuple.new)))
+      CR
+  end
+
+  it "supports 1 to n assignment, splat is empty (2)" do
+    run(<<-CR).to_b.should be_true
+      #{tuple_new}
+      #{range_new}
+
+      *x, _, _ = {1, 2}
+      x.is_a?(Tuple(*typeof(Tuple.new)))
+      CR
+  end
+
+  it "supports 1 to n assignment, splat is empty (3)" do
+    run(<<-CR).to_b.should be_true
+      #{tuple_new}
+      #{range_new}
+
+      _, _, *x = {1, 2}
+      x.is_a?(Tuple(*typeof(Tuple.new)))
+      CR
+  end
+
+  it "supports 1 to n assignment, raises if too short" do
+    run(<<-CR).to_b.should be_true
+      require "prelude"
+
+      begin
+        a, *b, c = [1]
+        false
+      rescue ex : IndexError
+        ex.message == "Multiple assignment count mismatch"
+      end
+      CR
+  end
+
+  it "supports 1 to n assignment, raises if out of bounds (1)" do
+    run(<<-CR).to_b.should be_true
+      require "prelude"
+
+      begin
+        *a, b, c = [1]
+        false
+      rescue ex : IndexError
+        true
+      end
+      CR
+  end
+
+  it "supports 1 to n assignment, raises if out of bounds (2)" do
+    run(<<-CR).to_b.should be_true
+      require "prelude"
+
+      begin
+        a, b, *c = [1]
+        false
+      rescue ex : IndexError
+        true
+      end
+      CR
+  end
+end
+
+private def tuple_new
+  <<-CR
+    struct Tuple
+      def self.new(*args)
+        args
+      end
+    end
+  CR
+end
+
+private def range_new
+  <<-CR
+    struct Range(B, E)
+      def initialize(@begin : B, @end : E, @exclusive : Bool = false)
+      end
+    end
+  CR
+end

spec/compiler/formatter/formatter_spec.cr

@@ -647,6 +647,8 @@ describe Crystal::Formatter do
 
   assert_format "a , b  = 1  ,  2", "a, b = 1, 2"
   assert_format "a[1] , b[2] = 1  ,  2", "a[1], b[2] = 1, 2"
+  assert_format " * a = 1 ", "*a = 1"
+  assert_format " _ , *_ ,\na.foo  ,a.bar  =  1  ,  2,3", "_, *_, a.foo, a.bar = 1, 2, 3"
   assert_format "あ.い, う.え.お = 1, 2"
 
   assert_format "begin\n1\nensure\n2\nend", "begin\n  1\nensure\n  2\nend"