Merge #1103

1103: Array inference r=flodiebold a=Lapz

Fixes the final item in #394. The only problem is that infering the repeat cause some types to be infered twices.
i.e 
```rust
fn test() {
    let y = unknown;
    [y, &y];
}
```

results in the following diff:

```diff
[11; 48) '{     ...&y]; }': ()
[21; 22) 'y': &{unknown}
[25; 32) 'unknown': &{unknown}
-[38; 45) '[y, &y]': [&&{unknown}]
+[38; 45) '[y, &y]': [&&{unknown};usize]
[39; 40) 'y': &{unknown}
+[39; 40) 'y': &{unknown}
[42; 44) '&y': &&{unknown}
[43; 44) 'y': &{unknown}
```

Should the code produce two inference results for 'y' and if not could any tell me what needs to change.

Co-authored-by: Lenard Pratt <[email protected]>

2 files changed, 58 insertions, 45 deletions

diff --git a/crates/ra_hir/src/ty/infer.rs b/crates/ra_hir/src/ty/infer.rs
index 887153484..9ace6b13a 100644
--- a/crates/ra_hir/src/ty/infer.rs
+++ b/crates/ra_hir/src/ty/infer.rs
@@ -32,7 +32,7 @@ use crate::{
     DefWithBody,
     ImplItem,
     type_ref::{TypeRef, Mutability},
-    expr::{Body, Expr, BindingAnnotation, Literal, ExprId, Pat, PatId, UnaryOp, BinaryOp, Statement, FieldPat, self},
+    expr::{Body, Expr, BindingAnnotation, Literal, ExprId, Pat, PatId, UnaryOp, BinaryOp, Statement, FieldPat,Array, self},
     generics::GenericParams,
     path::{GenericArgs, GenericArg},
     adt::VariantDef,
@@ -1074,7 +1074,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
 
                 Ty::apply(TypeCtor::Tuple, Substs(ty_vec.into()))
             }
-            Expr::Array { exprs } => {
+            Expr::Array(array) => {
                 let elem_ty = match &expected.ty {
                     Ty::Apply(a_ty) => match a_ty.ctor {
                         TypeCtor::Slice | TypeCtor::Array => {
@@ -1085,8 +1085,21 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                     _ => self.new_type_var(),
                 };
 
-                for expr in exprs.iter() {
-                    self.infer_expr(*expr, &Expectation::has_type(elem_ty.clone()));
+                match array {
+                    Array::ElementList(items) => {
+                        for expr in items.iter() {
+                            self.infer_expr(*expr, &Expectation::has_type(elem_ty.clone()));
+                        }
+                    }
+                    Array::Repeat { initializer, repeat } => {
+                        self.infer_expr(*initializer, &Expectation::has_type(elem_ty.clone()));
+                        self.infer_expr(
+                            *repeat,
+                            &Expectation::has_type(Ty::simple(TypeCtor::Int(
+                                primitive::UncertainIntTy::Known(primitive::IntTy::usize()),
+                            ))),
+                        );
+                    }
                 }
 
                 Ty::apply_one(TypeCtor::Array, elem_ty)
diff --git a/crates/ra_hir/src/ty/tests.rs b/crates/ra_hir/src/ty/tests.rs
index f0164f7ea..f6a325033 100644
--- a/crates/ra_hir/src/ty/tests.rs
+++ b/crates/ra_hir/src/ty/tests.rs
@@ -697,58 +697,58 @@ fn test(x: &str, y: isize) {
 [9; 10) 'x': &str
 [18; 19) 'y': isize
 [28; 324) '{     ... 3]; }': ()
-[38; 39) 'a': [&str]
-[42; 45) '[x]': [&str]
+[38; 39) 'a': [&str;_]
+[42; 45) '[x]': [&str;_]
 [43; 44) 'x': &str
-[55; 56) 'b': [[&str]]
-[59; 65) '[a, a]': [[&str]]
-[60; 61) 'a': [&str]
-[63; 64) 'a': [&str]
-[75; 76) 'c': [[[&str]]]
-[79; 85) '[b, b]': [[[&str]]]
-[80; 81) 'b': [[&str]]
-[83; 84) 'b': [[&str]]
-[96; 97) 'd': [isize]
-[100; 112) '[y, 1, 2, 3]': [isize]
+[55; 56) 'b': [[&str;_];_]
+[59; 65) '[a, a]': [[&str;_];_]
+[60; 61) 'a': [&str;_]
+[63; 64) 'a': [&str;_]
+[75; 76) 'c': [[[&str;_];_];_]
+[79; 85) '[b, b]': [[[&str;_];_];_]
+[80; 81) 'b': [[&str;_];_]
+[83; 84) 'b': [[&str;_];_]
+[96; 97) 'd': [isize;_]
+[100; 112) '[y, 1, 2, 3]': [isize;_]
 [101; 102) 'y': isize
 [104; 105) '1': isize
 [107; 108) '2': isize
 [110; 111) '3': isize
-[122; 123) 'd': [isize]
-[126; 138) '[1, y, 2, 3]': [isize]
+[122; 123) 'd': [isize;_]
+[126; 138) '[1, y, 2, 3]': [isize;_]
 [127; 128) '1': isize
 [130; 131) 'y': isize
 [133; 134) '2': isize
 [136; 137) '3': isize
-[148; 149) 'e': [isize]
-[152; 155) '[y]': [isize]
+[148; 149) 'e': [isize;_]
+[152; 155) '[y]': [isize;_]
 [153; 154) 'y': isize
-[165; 166) 'f': [[isize]]
-[169; 175) '[d, d]': [[isize]]
-[170; 171) 'd': [isize]
-[173; 174) 'd': [isize]
-[185; 186) 'g': [[isize]]
-[189; 195) '[e, e]': [[isize]]
-[190; 191) 'e': [isize]
-[193; 194) 'e': [isize]
-[206; 207) 'h': [i32]
-[210; 216) '[1, 2]': [i32]
+[165; 166) 'f': [[isize;_];_]
+[169; 175) '[d, d]': [[isize;_];_]
+[170; 171) 'd': [isize;_]
+[173; 174) 'd': [isize;_]
+[185; 186) 'g': [[isize;_];_]
+[189; 195) '[e, e]': [[isize;_];_]
+[190; 191) 'e': [isize;_]
+[193; 194) 'e': [isize;_]
+[206; 207) 'h': [i32;_]
+[210; 216) '[1, 2]': [i32;_]
 [211; 212) '1': i32
 [214; 215) '2': i32
-[226; 227) 'i': [&str]
-[230; 240) '["a", "b"]': [&str]
+[226; 227) 'i': [&str;_]
+[230; 240) '["a", "b"]': [&str;_]
 [231; 234) '"a"': &str
 [236; 239) '"b"': &str
-[251; 252) 'b': [[&str]]
-[255; 265) '[a, ["b"]]': [[&str]]
-[256; 257) 'a': [&str]
-[259; 264) '["b"]': [&str]
+[251; 252) 'b': [[&str;_];_]
+[255; 265) '[a, ["b"]]': [[&str;_];_]
+[256; 257) 'a': [&str;_]
+[259; 264) '["b"]': [&str;_]
 [260; 263) '"b"': &str
-[275; 276) 'x': [u8]
-[288; 290) '[]': [u8]
-[300; 301) 'z': &[u8]
-[311; 321) '&[1, 2, 3]': &[u8]
-[312; 321) '[1, 2, 3]': [u8]
+[275; 276) 'x': [u8;_]
+[288; 290) '[]': [u8;_]
+[300; 301) 'z': &[u8;_]
+[311; 321) '&[1, 2, 3]': &[u8;_]
+[312; 321) '[1, 2, 3]': [u8;_]
 [313; 314) '1': u8
 [316; 317) '2': u8
 [319; 320) '3': u8"###
@@ -1553,7 +1553,7 @@ fn test() {
 [11; 48) '{     ...&y]; }': ()
 [21; 22) 'y': &{unknown}
 [25; 32) 'unknown': &{unknown}
-[38; 45) '[y, &y]': [&&{unknown}]
+[38; 45) '[y, &y]': [&&{unknown};_]
 [39; 40) 'y': &{unknown}
 [42; 44) '&y': &&{unknown}
 [43; 44) 'y': &{unknown}"###
@@ -1578,7 +1578,7 @@ fn test() {
 [25; 32) 'unknown': &&{unknown}
 [42; 43) 'y': &&{unknown}
 [46; 53) 'unknown': &&{unknown}
-[59; 77) '[(x, y..., &x)]': [(&&{unknown}, &&{unknown})]
+[59; 77) '[(x, y..., &x)]': [(&&{unknown}, &&{unknown});_]
 [60; 66) '(x, y)': (&&{unknown}, &&{unknown})
 [61; 62) 'x': &&{unknown}
 [64; 65) 'y': &&{unknown}
@@ -1670,8 +1670,8 @@ fn test_line_buffer() {
 "#),
         @r###"
 [23; 53) '{     ...n']; }': ()
-[29; 50) '&[0, b...b'\n']': &[u8]
-[30; 50) '[0, b'...b'\n']': [u8]
+[29; 50) '&[0, b...b'\n']': &[u8;_]
+[30; 50) '[0, b'...b'\n']': [u8;_]
 [31; 32) '0': u8
 [34; 39) 'b'\n'': u8
 [41; 42) '1': u8