Implement array functions with just an expression body

Author: dcodeIO

dist/assemblyscript.js

@@ -836,20 +836,27 @@ export class Compiler extends DiagnosticEmitter {
     var typeRef = this.ensureFunctionType(instance.signature);
     var module = this.module;
     if (body) {
+      let returnType = instance.signature.returnType;
 
       // compile body
       let previousFunction = this.currentFunction;
       this.currentFunction = instance;
-      let stmt = this.compileStatement(body);
-
-      // make sure all branches return
-      let allBranchesReturn = instance.flow.finalize();
-      let returnType = instance.signature.returnType;
-      if (returnType != Type.void && !allBranchesReturn) {
-        this.error(
-          DiagnosticCode.A_function_whose_declared_type_is_not_void_must_return_a_value,
-          assert(declaration.signature.returnType, "return type expected").range
-        );
+      let flow = instance.flow;
+      let stmt: ExpressionRef;
+      if (body.kind == NodeKind.EXPRESSION) { // () => expression
+        stmt = this.compileExpression((<ExpressionStatement>body).expression, returnType);
+        flow.set(FlowFlags.RETURNS);
+      } else {
+        assert(body.kind == NodeKind.BLOCK);
+        stmt = this.compileStatement(body);
+        // make sure all branches return
+        let allBranchesReturn = flow.finalize();
+        if (returnType != Type.void && !allBranchesReturn) {
+          this.error(
+            DiagnosticCode.A_function_whose_declared_type_is_not_void_must_return_a_value,
+            assert(declaration.signature.returnType, "return type expected").range
+          );
+        }
       }
       this.currentFunction = previousFunction;
 

dist/assemblyscript.js.map

@@ -2,12 +2,14 @@
  (type $ii (func (param i32) (result i32)))
  (type $iiiiv (func (param i32 i32 i32 i32)))
  (type $v (func))
+ (type $i (func (result i32)))
  (import "env" "abort" (func $abort (param i32 i32 i32 i32)))
  (global $function-expression/f1 (mut i32) (i32.const 0))
  (global $function-expression/f2 (mut i32) (i32.const 1))
  (global $function-expression/f3 (mut i32) (i32.const 2))
- (table 3 3 anyfunc)
- (elem (i32.const 0) $start~anonymous|0 $start~anonymous|0 $start~someName|2)
+ (global $function-expression/f4 (mut i32) (i32.const 3))
+ (table 4 4 anyfunc)
+ (elem (i32.const 0) $start~anonymous|0 $start~anonymous|0 $start~someName|2 $start~anonymous|3)
  (memory $0 1)
  (data (i32.const 4) "\16\00\00\00f\00u\00n\00c\00t\00i\00o\00n\00-\00e\00x\00p\00r\00e\00s\00s\00i\00o\00n\00.\00t\00s")
  (export "memory" (memory $0))
@@ -18,7 +20,10 @@
  (func $start~someName|2 (; 2 ;) (type $v)
   (nop)
  )
- (func $start (; 3 ;) (type $v)
+ (func $start~anonymous|3 (; 3 ;) (type $i) (result i32)
+  (i32.const 1)
+ )
+ (func $start (; 4 ;) (type $v)
   (if
    (i32.ne
     (call_indirect (type $ii)
@@ -58,5 +63,22 @@
   (call_indirect (type $v)
    (get_global $function-expression/f3)
   )
+  (if
+   (i32.ne
+    (call_indirect (type $i)
+     (get_global $function-expression/f4)
+    )
+    (i32.const 1)
+   )
+   (block
+    (call $abort
+     (i32.const 0)
+     (i32.const 4)
+     (i32.const 16)
+     (i32.const 0)
+    )
+    (unreachable)
+   )
+  )
  )
 )

src/compiler.ts

@@ -11,3 +11,6 @@ assert(f2(2) == 2);
 var f3 = function someName(): void {
 };
 f3();
+
+var f4 = (): i32 => 1;
+assert(f4() == 1);

tests/compiler/function-expression.optimized.wat

@@ -2,13 +2,15 @@
  (type $ii (func (param i32) (result i32)))
  (type $iiiiv (func (param i32 i32 i32 i32)))
  (type $v (func))
+ (type $i (func (result i32)))
  (import "env" "abort" (func $abort (param i32 i32 i32 i32)))
  (global $function-expression/f1 (mut i32) (i32.const 0))
  (global $function-expression/f2 (mut i32) (i32.const 1))
  (global $function-expression/f3 (mut i32) (i32.const 2))
+ (global $function-expression/f4 (mut i32) (i32.const 3))
  (global $HEAP_BASE i32 (i32.const 52))
- (table 3 3 anyfunc)
- (elem (i32.const 0) $start~anonymous|0 $start~anonymous|1 $start~someName|2)
+ (table 4 4 anyfunc)
+ (elem (i32.const 0) $start~anonymous|0 $start~anonymous|1 $start~someName|2 $start~anonymous|3)
  (memory $0 1)
  (data (i32.const 4) "\16\00\00\00f\00u\00n\00c\00t\00i\00o\00n\00-\00e\00x\00p\00r\00e\00s\00s\00i\00o\00n\00.\00t\00s\00")
  (export "memory" (memory $0))
@@ -25,7 +27,10 @@
  )
  (func $start~someName|2 (; 3 ;) (type $v)
  )
- (func $start (; 4 ;) (type $v)
+ (func $start~anonymous|3 (; 4 ;) (type $i) (result i32)
+  (i32.const 1)
+ )
+ (func $start (; 5 ;) (type $v)
   (if
    (i32.eqz
     (i32.eq
@@ -69,5 +74,24 @@
   (call_indirect (type $v)
    (get_global $function-expression/f3)
   )
+  (if
+   (i32.eqz
+    (i32.eq
+     (call_indirect (type $i)
+      (get_global $function-expression/f4)
+     )
+     (i32.const 1)
+    )
+   )
+   (block
+    (call $abort
+     (i32.const 0)
+     (i32.const 4)
+     (i32.const 16)
+     (i32.const 0)
+    )
+    (unreachable)
+   )
+  )
  )
 )