From a142beaf013a016a48eb9f193b55e0cbcb80b6a9 Mon Sep 17 00:00:00 2001
From: Lukas Wirth <lukastw97@gmail.com>
Date: Wed, 23 Dec 2020 12:24:24 +0100
Subject: Implement const block inference

---
 crates/hir_def/src/body/lower.rs  |  4 ++++
 crates/hir_def/src/expr.rs        |  8 +++++++-
 crates/hir_ty/src/infer/expr.rs   |  2 +-
 crates/hir_ty/src/tests/simple.rs | 13 +++++++++----
 crates/syntax/src/ast/expr_ext.rs |  4 ++++
 5 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/crates/hir_def/src/body/lower.rs b/crates/hir_def/src/body/lower.rs
index 4492a7d77..1b98504bb 100644
--- a/crates/hir_def/src/body/lower.rs
+++ b/crates/hir_def/src/body/lower.rs
@@ -246,6 +246,10 @@ impl ExprCollector<'_> {
                     let body = self.collect_block_opt(e.block_expr());
                     self.alloc_expr(Expr::Async { body }, syntax_ptr)
                 }
+                ast::Effect::Const(_) => {
+                    let body = self.collect_block_opt(e.block_expr());
+                    self.alloc_expr(Expr::Const { body }, syntax_ptr)
+                }
             },
             ast::Expr::BlockExpr(e) => self.collect_block(e),
             ast::Expr::LoopExpr(e) => {
diff --git a/crates/hir_def/src/expr.rs b/crates/hir_def/src/expr.rs
index b1e57c693..3bba30397 100644
--- a/crates/hir_def/src/expr.rs
+++ b/crates/hir_def/src/expr.rs
@@ -114,6 +114,9 @@ pub enum Expr {
     Async {
         body: ExprId,
     },
+    Const {
+        body: ExprId,
+    },
     Cast {
         expr: ExprId,
         type_ref: TypeRef,
@@ -253,7 +256,10 @@ impl Expr {
                     f(*expr);
                 }
             }
-            Expr::TryBlock { body } | Expr::Unsafe { body } | Expr::Async { body } => f(*body),
+            Expr::TryBlock { body }
+            | Expr::Unsafe { body }
+            | Expr::Async { body }
+            | Expr::Const { body } => f(*body),
             Expr::Loop { body, .. } => f(*body),
             Expr::While { condition, body, .. } => {
                 f(*condition);
diff --git a/crates/hir_ty/src/infer/expr.rs b/crates/hir_ty/src/infer/expr.rs
index 2cdce2cef..744569e6e 100644
--- a/crates/hir_ty/src/infer/expr.rs
+++ b/crates/hir_ty/src/infer/expr.rs
@@ -155,7 +155,7 @@ impl<'a> InferenceContext<'a> {
                 }
                 None => self.infer_block(statements, *tail, expected),
             },
-            Expr::Unsafe { body } => self.infer_expr(*body, expected),
+            Expr::Unsafe { body } | Expr::Const { body } => self.infer_expr(*body, expected),
             Expr::TryBlock { body } => {
                 let _inner = self.infer_expr(*body, expected);
                 // FIXME should be std::result::Result<{inner}, _>
diff --git a/crates/hir_ty/src/tests/simple.rs b/crates/hir_ty/src/tests/simple.rs
index a569223b4..a61282d5a 100644
--- a/crates/hir_ty/src/tests/simple.rs
+++ b/crates/hir_ty/src/tests/simple.rs
@@ -1894,6 +1894,7 @@ fn effects_smoke_test() {
             let x = unsafe { 92 };
             let y = async { async { () }.await };
             let z = try { () };
+            let w = const { 92 };
             let t = 'a: { 92 };
         }
 
@@ -1905,7 +1906,7 @@ fn effects_smoke_test() {
         }
         "#,
         expect![[r#"
-            16..136 '{     ...2 }; }': ()
+            16..162 '{     ...2 }; }': ()
             26..27 'x': i32
             30..43 'unsafe { 92 }': i32
             37..43 '{ 92 }': i32
@@ -1921,9 +1922,13 @@ fn effects_smoke_test() {
             99..109 'try { () }': {unknown}
             103..109 '{ () }': ()
             105..107 '()': ()
-            119..120 't': i32
-            127..133 '{ 92 }': i32
-            129..131 '92': i32
+            119..120 'w': i32
+            123..135 'const { 92 }': i32
+            129..135 '{ 92 }': i32
+            131..133 '92': i32
+            145..146 't': i32
+            153..159 '{ 92 }': i32
+            155..157 '92': i32
         "#]],
     )
 }
diff --git a/crates/syntax/src/ast/expr_ext.rs b/crates/syntax/src/ast/expr_ext.rs
index e4a9b945c..636ce166d 100644
--- a/crates/syntax/src/ast/expr_ext.rs
+++ b/crates/syntax/src/ast/expr_ext.rs
@@ -358,6 +358,7 @@ pub enum Effect {
     Async(SyntaxToken),
     Unsafe(SyntaxToken),
     Try(SyntaxToken),
+    Const(SyntaxToken),
     // Very much not an effect, but we stuff it into this node anyway
     Label(ast::Label),
 }
@@ -373,6 +374,9 @@ impl ast::EffectExpr {
         if let Some(token) = self.try_token() {
             return Effect::Try(token);
         }
+        if let Some(token) = self.const_token() {
+            return Effect::Const(token);
+        }
         if let Some(label) = self.label() {
             return Effect::Label(label);
         }
-- 
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