From 436b19c408a2eed3b400eafd6889eacb6ab5ea32 Mon Sep 17 00:00:00 2001
From: Swastik Baranwal <swstkbaranwal@gmail.com>
Date: Sun, 4 Sep 2022 16:45:26 +0530
Subject: [PATCH] checker: add error for mismatched types and format character
 for string interpolation (#15639)

---
 vlib/v/checker/str.v                          |  7 +++
 .../tests/str_interpol_invalid_err.out        | 55 +++++++++++++++++++
 .../checker/tests/str_interpol_invalid_err.vv | 16 ++++++
 3 files changed, 78 insertions(+)
 create mode 100644 vlib/v/checker/tests/str_interpol_invalid_err.out
 create mode 100644 vlib/v/checker/tests/str_interpol_invalid_err.vv

diff --git a/vlib/v/checker/str.v b/vlib/v/checker/str.v
index 8eea09bca..de4cdc26b 100644
--- a/vlib/v/checker/str.v
+++ b/vlib/v/checker/str.v
@@ -94,6 +94,13 @@ pub fn (mut c Checker) string_inter_lit(mut node ast.StringInterLiteral) ast.Typ
 				c.error('illegal format specifier `${fmt:c}` for type `${c.table.get_type_name(ftyp)}`',
 					node.fmt_poss[i])
 			}
+			// v fmt doesn't format this correctly
+			if
+				c.table.final_sym(typ).kind in [.array, .array_fixed, .struct_, .interface_, .none_, .map, .sum_type]
+				&& fmt in [`E`, `F`, `G`, `e`, `f`, `g`, `d`, `u`, `x`, `X`, `o`, `c`, `p`, `b`] {
+				c.error('illegal format specifier `${fmt:c}` for type `${c.table.get_type_name(ftyp)}`',
+					node.fmt_poss[i])
+			}
 			node.need_fmts[i] = fmt != c.get_default_fmt(ftyp, typ)
 		}
 		// check recursive str
diff --git a/vlib/v/checker/tests/str_interpol_invalid_err.out b/vlib/v/checker/tests/str_interpol_invalid_err.out
new file mode 100644
index 000000000..41c68f042
--- /dev/null
+++ b/vlib/v/checker/tests/str_interpol_invalid_err.out
@@ -0,0 +1,55 @@
+vlib/v/checker/tests/str_interpol_invalid_err.vv:8:13: error: illegal format specifier `x` for type `[]int`
+    6 |
+    7 | fn main() {
+    8 |     _ = '${[1]:x}'
+      |                ^
+    9 |     _ = '${[1]!:x}'
+   10 |     _ = '${Foo{}:x}'
+vlib/v/checker/tests/str_interpol_invalid_err.vv:9:14: error: illegal format specifier `x` for type `[1]int`
+    7 | fn main() {
+    8 |     _ = '${[1]:x}'
+    9 |     _ = '${[1]!:x}'
+      |                 ^
+   10 |     _ = '${Foo{}:x}'
+   11 |     _ = '${[1]:f}'
+vlib/v/checker/tests/str_interpol_invalid_err.vv:10:15: error: illegal format specifier `x` for type `Foo`
+    8 |     _ = '${[1]:x}'
+    9 |     _ = '${[1]!:x}'
+   10 |     _ = '${Foo{}:x}'
+      |                  ^
+   11 |     _ = '${[1]:f}'
+   12 |     _ := '${none:F}'
+vlib/v/checker/tests/str_interpol_invalid_err.vv:11:13: error: illegal format specifier `f` for type `[]int`
+    9 |     _ = '${[1]!:x}'
+   10 |     _ = '${Foo{}:x}'
+   11 |     _ = '${[1]:f}'
+      |                ^
+   12 |     _ := '${none:F}'
+   13 |     _ = '${{"a": "b"}:x}'
+vlib/v/checker/tests/str_interpol_invalid_err.vv:12:15: error: illegal format specifier `F` for type `none`
+   10 |     _ = '${Foo{}:x}'
+   11 |     _ = '${[1]:f}'
+   12 |     _ := '${none:F}'
+      |                  ^
+   13 |     _ = '${{"a": "b"}:x}'
+   14 |     _ = '${Alias(Foo{}):x}'
+vlib/v/checker/tests/str_interpol_invalid_err.vv:13:20: error: illegal format specifier `x` for type `map[string]string`
+   11 |     _ = '${[1]:f}'
+   12 |     _ := '${none:F}'
+   13 |     _ = '${{"a": "b"}:x}'
+      |                       ^
+   14 |     _ = '${Alias(Foo{}):x}'
+   15 |     _ = '${SumType(int(5)):o}'
+vlib/v/checker/tests/str_interpol_invalid_err.vv:14:22: error: illegal format specifier `x` for type `Alias`
+   12 |     _ := '${none:F}'
+   13 |     _ = '${{"a": "b"}:x}'
+   14 |     _ = '${Alias(Foo{}):x}'
+      |                         ^
+   15 |     _ = '${SumType(int(5)):o}'
+   16 | }
+vlib/v/checker/tests/str_interpol_invalid_err.vv:15:25: error: illegal format specifier `o` for type `SumType`
+   13 |     _ = '${{"a": "b"}:x}'
+   14 |     _ = '${Alias(Foo{}):x}'
+   15 |     _ = '${SumType(int(5)):o}'
+      |                            ^
+   16 | }
diff --git a/vlib/v/checker/tests/str_interpol_invalid_err.vv b/vlib/v/checker/tests/str_interpol_invalid_err.vv
new file mode 100644
index 000000000..b938fcfc5
--- /dev/null
+++ b/vlib/v/checker/tests/str_interpol_invalid_err.vv
@@ -0,0 +1,16 @@
+struct Foo {}
+
+type Alias = Foo
+
+type SumType = Alias | int
+
+fn main() {
+	_ = '${[1]:x}'
+	_ = '${[1]!:x}'
+	_ = '${Foo{}:x}'
+	_ = '${[1]:f}'
+	_ := '${none:F}'
+	_ = '${{"a": "b"}:x}'
+	_ = '${Alias(Foo{}):x}'
+	_ = '${SumType(int(5)):o}'
+}
-- 
2.30.2