fix(compiler): could not hydrate optionals (#3741)

There are several open issues in progress that need to be able to define generic optionals. Such as: - #1868 - #3575 - #3653 I only added `tryAt` method for Array since the actual work is defined in another issue, but I needed an example to write some test cases with. Since there are several efforts that need this change I opted to not wait and include it in one of those PRs but just add the support here so other efforts can rebase. ## Checklist - [x] Title matches [Winglang's style guide](https://www.winglang.io/contributing/start-here/pull_requests#how-are-pull-request-titles-formatted) - [x] Description explains motivation and solution - [x] Tests added (always) - [x] Docs updated (only required for features) - [x] Added `pr/e2e-full` label if this feature requires end-to-end testing *By submitting this pull request, I confirm that my contribution is made under the terms of the [Wing Cloud Contribution License](https://github.com/winglang/wing/blob/main/CONTRIBUTION_LICENSE.md)*.
winglang · Aug 8, 2023 · 6338ad7 · 6338ad7
1 parent af35df3
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diff --git a/docs/docs/04-standard-library/02-std/api-reference.md b/docs/docs/04-standard-library/02-std/api-reference.md
@@ -29,6 +29,7 @@ Immutable Array.
 | <code><a href="#@winglang/sdk.std.Array.indexOf">indexOf</a></code> | Returns the index of the first occurrence of searchElement found. |
 | <code><a href="#@winglang/sdk.std.Array.join">join</a></code> | Returns a new string containing the concatenated values in this array, separated by commas or a specified separator string. |
 | <code><a href="#@winglang/sdk.std.Array.lastIndexOf">lastIndexOf</a></code> | Returns the index of the last occurrence of searchElement found. |
+| <code><a href="#@winglang/sdk.std.Array.tryAt">tryAt</a></code> | Get the value at the given index, returning nil if the index is out of bounds. |
 
 ---
 
@@ -137,6 +138,22 @@ to search for.
 
 ---
 
+##### `tryAt` <a name="tryAt" id="@winglang/sdk.std.Array.tryAt"></a>
+
+```wing
+tryAt(index: num): <T>
+```
+
+Get the value at the given index, returning nil if the index is out of bounds.
+
+###### `index`<sup>Required</sup> <a name="index" id="@winglang/sdk.std.Array.tryAt.parameter.index"></a>
+
+- *Type:* num
+
+index of the value to get.
+
+---
+
 
 #### Properties <a name="Properties" id="Properties"></a>
 

diff --git a/examples/tests/invalid/container_types.w b/examples/tests/invalid/container_types.w
@@ -5,6 +5,10 @@ let arr3 = Array<str>["hello"];
 let arr4: Array<num> = arr3;
 arr1.someRandomMethod();
 
+let arr5: Array<num> = [1, 2, 3];
+let val: num = arr5.tryAt(0);
+//             ^^^^^^^^^^^^^ Expected type to be "num", but got "num?" instead
+
 //Map tests
 let m1: Map<num> = {"a" => 1, "b" => "2", "c" => 3};
 let m2: Map<num> = ["a" => 1, "b" => "2", "c" => 3];

diff --git a/examples/tests/valid/container_types.w b/examples/tests/valid/container_types.w
@@ -31,6 +31,16 @@ let arr7: Array<num> = arr4;
 assert(arr7.length == 3);
 assert(arr7.at(1) == 2);
 
+if let val = emptyArray.tryAt(0) {
+  assert(false); // Should not happen
+}
+
+if let val = arr1.tryAt(0) {
+  assert(val == 1);
+} else {
+  assert(false); // Should not happen
+}
+
 //Map tests
 let emptyMap = Map<num>{};
 assert(emptyMap.size() == 0);

diff --git a/libs/wingc/src/type_check.rs b/libs/wingc/src/type_check.rs
@@ -3839,7 +3839,6 @@ impl<'a> TypeChecker<'a> {
 					// Replace type params in function signatures
 					if let Some(sig) = v.as_function_sig() {
 						let new_return_type = self.get_concrete_type_for_generic(sig.return_type, &types_map);
-
 						let new_this_type = if let Some(this_type) = sig.this_type {
 							Some(self.get_concrete_type_for_generic(this_type, &types_map))
 						} else {
@@ -3932,6 +3931,11 @@ impl<'a> TypeChecker<'a> {
 		} else {
 			// Handle generic return types
 			// TODO: If a generic class has a method that returns another generic, it must be a builtin
+			if let Type::Optional(t) = *type_to_maybe_replace {
+				let concrete_t = self.get_concrete_type_for_generic(t, types_map);
+				return self.types.add_type(Type::Optional(concrete_t));
+			}
+
 			if let Some(c) = type_to_maybe_replace.as_class() {
 				if let Some(type_parameters) = &c.type_parameters {
 					// For now all our generics only have a single type parameter so use the first type parameter as our "T1"
@@ -3942,6 +3946,7 @@ impl<'a> TypeChecker<'a> {
 						.map(|(_, n)| n)
 						.expect("generic must have a type parameter");
 					let fqn = format!("{}.{}", WINGSDK_STD_MODULE, c.name.name);
+
 					return match fqn.as_str() {
 						WINGSDK_MUT_ARRAY => self.types.add_type(Type::MutArray(t1_replacement)),
 						WINGSDK_ARRAY => self.types.add_type(Type::Array(t1_replacement)),

diff --git a/libs/wingsdk/src/std/array.ts b/libs/wingsdk/src/std/array.ts
@@ -38,6 +38,19 @@ export class Array {
     throw new Error("Abstract");
   }
 
+  /**
+   * Get the value at the given index, returning nil if the index is out of bounds.
+   *
+   * @macro ($self$.at($args$))
+   *
+   * @param index index of the value to get
+   * @returns the value at the given index, or undefined if the index is out of bounds
+   */
+  public tryAt(index: number): T1 | undefined {
+    index;
+    throw new Error("Macro");
+  }
+
   /**
    * Merge arr to the end of this array
    * @param arr array to merge

diff --git a/tools/hangar/__snapshots__/invalid.ts.snap b/tools/hangar/__snapshots__/invalid.ts.snap
@@ -461,23 +461,23 @@ Duration <DURATION>"
 
 exports[`container_types.w 1`] = `
 "error: Unknown parser error
-   --> ../../../examples/tests/invalid/container_types.w:10:25
+   --> ../../../examples/tests/invalid/container_types.w:14:25
    |
-10 | let m2: Map<num> = [\\"a\\" => 1, \\"b\\" => \\"2\\", \\"c\\" => 3];
+14 | let m2: Map<num> = [\\"a\\" => 1, \\"b\\" => \\"2\\", \\"c\\" => 3];
    |                         ^^^^ Unknown parser error
 
 
 error: Unexpected 'string'
-   --> ../../../examples/tests/invalid/container_types.w:10:31
+   --> ../../../examples/tests/invalid/container_types.w:14:31
    |
-10 | let m2: Map<num> = [\\"a\\" => 1, \\"b\\" => \\"2\\", \\"c\\" => 3];
+14 | let m2: Map<num> = [\\"a\\" => 1, \\"b\\" => \\"2\\", \\"c\\" => 3];
    |                               ^^^ Unexpected 'string'
 
 
 error: Unknown parser error
-   --> ../../../examples/tests/invalid/container_types.w:10:47
+   --> ../../../examples/tests/invalid/container_types.w:14:47
    |
-10 | let m2: Map<num> = [\\"a\\" => 1, \\"b\\" => \\"2\\", \\"c\\" => 3];
+14 | let m2: Map<num> = [\\"a\\" => 1, \\"b\\" => \\"2\\", \\"c\\" => 3];
    |                                               ^^^^ Unknown parser error
 
 
@@ -509,87 +509,94 @@ error: Unknown symbol \\"someRandomMethod\\"
   |      ^^^^^^^^^^^^^^^^ Unknown symbol \\"someRandomMethod\\"
 
 
-error: Expected type to be \\"num\\", but got \\"str\\" instead
-  --> ../../../examples/tests/invalid/container_types.w:9:38
+error: Expected type to be \\"num\\", but got \\"num?\\" instead
+  --> ../../../examples/tests/invalid/container_types.w:9:16
   |
-9 | let m1: Map<num> = {\\"a\\" => 1, \\"b\\" => \\"2\\", \\"c\\" => 3};
-  |                                      ^^^ Expected type to be \\"num\\", but got \\"str\\" instead
+9 | let val: num = arr5.tryAt(0);
+  |                ^^^^^^^^^^^^^ Expected type to be \\"num\\", but got \\"num?\\" instead
+
+
+error: Expected type to be \\"num\\", but got \\"str\\" instead
+   --> ../../../examples/tests/invalid/container_types.w:13:38
+   |
+13 | let m1: Map<num> = {\\"a\\" => 1, \\"b\\" => \\"2\\", \\"c\\" => 3};
+   |                                      ^^^ Expected type to be \\"num\\", but got \\"str\\" instead
 
 
 error: Expected type to be \\"Map<num>\\", but got \\"Array<str>\\" instead
-   --> ../../../examples/tests/invalid/container_types.w:10:20
+   --> ../../../examples/tests/invalid/container_types.w:14:20
    |
-10 | let m2: Map<num> = [\\"a\\" => 1, \\"b\\" => \\"2\\", \\"c\\" => 3];
+14 | let m2: Map<num> = [\\"a\\" => 1, \\"b\\" => \\"2\\", \\"c\\" => 3];
    |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Expected type to be \\"Map<num>\\", but got \\"Array<str>\\" instead
 
 
 error: Expected type to be \\"Map<num>\\", but got \\"Map<str>\\" instead
-   --> ../../../examples/tests/invalid/container_types.w:12:20
+   --> ../../../examples/tests/invalid/container_types.w:16:20
    |
-12 | let m4: Map<num> = m3;
+16 | let m4: Map<num> = m3;
    |                    ^^ Expected type to be \\"Map<num>\\", but got \\"Map<str>\\" instead
 
 
 error: Unknown symbol \\"someRandomMethod\\"
-   --> ../../../examples/tests/invalid/container_types.w:13:4
+   --> ../../../examples/tests/invalid/container_types.w:17:4
    |
-13 | m1.someRandomMethod();
+17 | m1.someRandomMethod();
    |    ^^^^^^^^^^^^^^^^ Unknown symbol \\"someRandomMethod\\"
 
 
 error: Expected type to be \\"num\\", but got \\"str\\" instead
-   --> ../../../examples/tests/invalid/container_types.w:16:24
+   --> ../../../examples/tests/invalid/container_types.w:20:24
    |
-16 | let s1: Set<num> = {1, \\"2\\", 3};
+20 | let s1: Set<num> = {1, \\"2\\", 3};
    |                        ^^^ Expected type to be \\"num\\", but got \\"str\\" instead
 
 
 error: Expected \\"Array\\" type, found \\"Set<num>\\"
-   --> ../../../examples/tests/invalid/container_types.w:17:10
+   --> ../../../examples/tests/invalid/container_types.w:21:10
    |
-17 | let s2 = Set<num> [1, \\"2\\", 3];
+21 | let s2 = Set<num> [1, \\"2\\", 3];
    |          ^^^^^^^^^^^^^^^^^^^^ Expected \\"Array\\" type, found \\"Set<num>\\"
 
 
 error: Expected type to be \\"num\\", but got \\"str\\" instead
-   --> ../../../examples/tests/invalid/container_types.w:17:23
+   --> ../../../examples/tests/invalid/container_types.w:21:23
    |
-17 | let s2 = Set<num> [1, \\"2\\", 3];
+21 | let s2 = Set<num> [1, \\"2\\", 3];
    |                       ^^^ Expected type to be \\"num\\", but got \\"str\\" instead
 
 
 error: Expected type to be \\"num\\", but got \\"str\\" instead
-   --> ../../../examples/tests/invalid/container_types.w:18:24
+   --> ../../../examples/tests/invalid/container_types.w:22:24
    |
-18 | let s3: Set<num> = [1, \\"2\\", 3];
+22 | let s3: Set<num> = [1, \\"2\\", 3];
    |                        ^^^ Expected type to be \\"num\\", but got \\"str\\" instead
 
 
 error: Expected type to be \\"Set<num>\\", but got \\"Array<num>\\" instead
-   --> ../../../examples/tests/invalid/container_types.w:18:20
+   --> ../../../examples/tests/invalid/container_types.w:22:20
    |
-18 | let s3: Set<num> = [1, \\"2\\", 3];
+22 | let s3: Set<num> = [1, \\"2\\", 3];
    |                    ^^^^^^^^^^^ Expected type to be \\"Set<num>\\", but got \\"Array<num>\\" instead
 
 
 error: Expected type to be \\"Set<str>\\", but got \\"Set<num>\\" instead
-   --> ../../../examples/tests/invalid/container_types.w:20:20
+   --> ../../../examples/tests/invalid/container_types.w:24:20
    |
-20 | let s5: Set<str> = s4;
+24 | let s5: Set<str> = s4;
    |                    ^^ Expected type to be \\"Set<str>\\", but got \\"Set<num>\\" instead
 
 
 error: Unknown symbol \\"someRandomMethod\\"
-   --> ../../../examples/tests/invalid/container_types.w:21:4
+   --> ../../../examples/tests/invalid/container_types.w:25:4
    |
-21 | s1.someRandomMethod();
+25 | s1.someRandomMethod();
    |    ^^^^^^^^^^^^^^^^ Unknown symbol \\"someRandomMethod\\"
 
 
 error: Expected type to be \\"Array<str>\\", but got \\"MutArray<str>\\" instead
-   --> ../../../examples/tests/invalid/container_types.w:23:21
+   --> ../../../examples/tests/invalid/container_types.w:27:21
    |
-23 | let a: Array<str> = MutArray<str>[];
+27 | let a: Array<str> = MutArray<str>[];
    |                     ^^^^^^^^^^^^^^^ Expected type to be \\"Array<str>\\", but got \\"MutArray<str>\\" instead
 
 

diff --git a/tools/hangar/__snapshots__/test_corpus/valid/container_types.w_compile_tf-aws.md b/tools/hangar/__snapshots__/test_corpus/valid/container_types.w_compile_tf-aws.md
@@ -195,6 +195,23 @@ class $Root extends $stdlib.std.Resource {
     const arr7 = arr4;
     {((cond) => {if (!cond) throw new Error("assertion failed: arr7.length == 3")})((((a,b) => { try { return require('assert').deepStrictEqual(a,b) === undefined; } catch { return false; } })(arr7.length,3)))};
     {((cond) => {if (!cond) throw new Error("assertion failed: arr7.at(1) == 2")})((((a,b) => { try { return require('assert').deepStrictEqual(a,b) === undefined; } catch { return false; } })((arr7.at(1)),2)))};
+    {
+      const $IF_LET_VALUE = (emptyArray.at(0));
+      if ($IF_LET_VALUE != undefined) {
+        const val = $IF_LET_VALUE;
+        {((cond) => {if (!cond) throw new Error("assertion failed: false")})(false)};
+      }
+    }
+    {
+      const $IF_LET_VALUE = (arr1.at(0));
+      if ($IF_LET_VALUE != undefined) {
+        const val = $IF_LET_VALUE;
+        {((cond) => {if (!cond) throw new Error("assertion failed: val == 1")})((((a,b) => { try { return require('assert').deepStrictEqual(a,b) === undefined; } catch { return false; } })(val,1)))};
+      }
+      else {
+        {((cond) => {if (!cond) throw new Error("assertion failed: false")})(false)};
+      }
+    }
     const emptyMap = ({});
     {((cond) => {if (!cond) throw new Error("assertion failed: emptyMap.size() == 0")})((((a,b) => { try { return require('assert').deepStrictEqual(a,b) === undefined; } catch { return false; } })(Object.keys(emptyMap).length,0)))};
     const emptyMap2 = ({});